Posts Tagged ‘Circulatory system’

Mechanical Circulatory Assist Devices as a Bridge to Heart Transplantation or as “Destination Therapy“: Options for Patients in Advanced Heart Failure

Writer and Curator: Larry H. Bernstein, MD, FCAP


Curator: Aviva Lev-Ari, PhD, RN 


UPDATED on 10/22/2018

HeartMate 3 gets FDA approval for extended use

Revamped Abbott Labs device is seen as an option for cardiac patients who are unlikely to get transplants.

“When heart failure (HF) progresses to an advanced stage, difficult decisions must be made,” the AHA says on its website. “Do I want to receive aggressive treatment? Is quality of life more important than living as long as possible? How do I feel about resuscitation?”

LVADs can take over the pumping function of a failing heart, but they also present some of the most expensive implantable-device surgeries. An article in the peer-reviewed journal JACC: Heart Failure reported last year that the average total cost to implant an LVAD in Medicare beneficiaries was $175,000, more than double the cost of a heart transplant.

Amador said between 5,000 and 5,500 Americans will have LVAD implants this year. That compares with 2,200 adult heart transplants that happen annually in the U.S., according to the JACC article.

Starling RC.
Cleve Clin J Med. 2013 Jan; 80(1):33-40.

For patients with advanced heart failure, outcomes are good after heart transplantation, but not enough donor hearts are available. Fortunately, mechanical circulatory assist devices have become an excellent option and should be considered either as a bridge to transplantation or as “destination therapy.” Current mechanical circulatory assist devices improve quality of life in patients who are candidates.
For some patients, conventional treatments are inadequate to relieve the effects of heart failure. Under these circumstances, mechanical circulatory support is considered. There are now a variety of devices capable of pumping blood to restore circulation of vital organs, even temporarily replacing the function of the native heart.

The ABIOMED AB5000™ Circulatory Support System is a short-term mechanical system that can provide left, right, or biventricular support for patients whose hearts have failed but have the potential for recovery. The AB5000™ can be used to support the heart, giving it time to rest – and potentially recover native heart function. The device can also be used as a bridge to definitive therapy.


CardioWest™ temporary Total Artificial Heart (TAH-t)
This medical device is the modern version of the Jarvik 7 artificial heart first implanted into Barney Clark in 1982. The CardioWest™ temporary Total Artificial Heart is the only FDA approved temporary total artificial heart in the world.
The TAH-t is used as a bridge to heart transplant for eligible patients suffering from end-stage biventricular failure.


Other related articles published on this Scientific Journal include the following:

Ventricular Assist Device (VAD): A Recommended Approach to the Treatment of Intractable Cardiogenic Shock (larryhbern)

Trans-apical Transcatheter Aortic Valve Replacement in a Patient with Severe and Complex Left Main Coronary Artery Disease (LMCAD) (larryhbern)
Clinical Indications for Use of Inhaled Nitric Oxide (iNO) in the Adult Patient Market: Clinical Outcomes after Use, Therapy Demand and Cost of Care (Aviva Lev-Ari)

Gene Therapy Into Healthy Heart Muscle: Reprogramming Scar Tissue In Damaged Hearts
(Aviva Lev-Ari)

Heart Renewal by pre-existing Cardiomyocytes: Source of New Heart Cell Growth Discovered
(Aviva Lev-Ari)

Heart Remodeling by Design – Implantable Synchronized Cardiac Assist Device: Abiomed’s Symphony (Aviva Lev-Ari)

Economic Toll of Heart Failure in the US: Forecasting the Impact of Heart Failure in the United States – A Policy Statement From the American Heart Association (Aviva Lev-Ari)

Stenosis, Ischemia and Heart Failure (Aviva Lev-Ari)

Congestive Heart Failure & Personalized Medicine: Two-gene Test predicts response to Beta Blocker Bucindolol (Aviva Lev-Ari)

Phrenic Nerve Stimulation in Patients with Cheyne-Stokes Respiration and Congestive Heart Failure (larryhbern)

First Drug to improve Heart Failure Mortality in Over a Decade – (Aviva Lev-Ari)

Meta-analysis: Heart Failure Worsens Short-term Prognosis of NSTE-ACS Patients – TCTMD
(Aviva Lev-Ari)

THYMOSIN (Aviva Lev-Ari)

Resident-cell-based Therapy (Aviva Lev-Ari)

Amyloidosis with Cardiomyopathy (larryhbern)

Blood-vessels-generating stem cells discovered (ritu.saxena)

Stem Cell Research — The Frontier is at the Technion in Israel (A Lev-Ari)

Implantable Synchronized Cardiac Assist Device Designed for Heart Remodeling: Abiomed’s Symphony

Aviva Lev-Ari, PhD, RN


What is Acute Heart Failure?

What is Acute Heart Failure? (Photo credit: Novartis AG)

English: The CardioWest™ temporary Total Artif...

English: The CardioWest™ temporary Total Artificial Heart (Photo credit: Wikipedia)

English: Graph showing the correlation between...

English: Graph showing the correlation between BNP serum level and mortality. Source: Inder S. Anand, Lloyd D. Fisher, Yann-Tong Chiang, Roberto Latini, Serge Masson,Aldo P. Maggioni, Robert D. Glazer, Gianni Tognoni, Jay N. Cohn (24th Feb 2003). Changes in Brain Natriuretic Peptide and Norepinephrine Over Time and Mortality and Morbidity in the Valsartan Heart Failure Trial (Val-HeFT). Circulation 107: 1278-83. DOI: 10.1161/01.CIR.0000054164.99881.00 (Photo credit: Wikipedia)


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Pros and Cons of Drug Stabilizers for Arterial  Elasticity as an Alternative or Adjunct to Diuretics and Vasodilators in the Management of Hypertension.

Author, and Content Consultant to e-SERIES A: Cardiovascular Diseases: Justin Pearlman, MD, PhD, FACC


Article Curator: Aviva Lev-Ari, PhD, RN

This article presents the 2013 Thought Frontier on Hypertension and Vascular Compliance.

Conceptual development of the subject is presented in the following nine parts:

1.        Physiology of Circulation and Role of Arterial Elasticity

2.      Isolated Systolic Hypertension caused by Arterial Stiffening may be inadequately treated by Diuretics or Vasodilatation Antihypertensive Medications

3.         Physiology of Circulation and Compensatory Mechanism of Arterial Elasticity

4.         Vascular Compliance – The Potential for Novel Therapies

  • Novel Mechanism for Disease Etiology: Modulation of Nuclear and Cytoskeletal Actin Polymerization.
  • Genetic Therapy targeting Vascular Conductivity 
  • Regenerative Medicine for Vasculature Function Protection

5.        In addition to curtailing high pressures, stabilizing BP variability is a potential target for management of hypertension

6.        Mathematical Modeling: Arterial stiffening  explains much of primary hypertension

7.         Classification of Blood Pressure and Hypertensive Treatment Best Practice of Care in the US

8.         Genetic Risk for High Blood Pressure

9.         Is it Hypertension or Physical Inactivity: Cardiovascular Risk and Mortality – New results in 3/2013.

Summary By Justin D. Pearlman MD ME PhD MA FACC

1.       Physiology of Circulation and Role of Arterial Elasticity

  • Simplistically, high blood pressure stems from too much volume (salt water) for the vascular space, or conversely, too little space for the volume. Biological signals, such as endothelin, hypoxia, acidosis, nitric oxide, can modify vascular volume by constricting muscles in blood vessel walls. Less simplistically the physics of circulation are governed by numerous factors, with essentials detailed below.
  • The vascular space has two major circuits: pulmonary (lungs) and systemic (body).
  • Compliance (C)  relates change in volume (ΔV) to change in pressure (ΔP) as a measure of the strength of elasticity, where elasticity summarizes the intrinsic forces that  return to original shape after deformation: C = ΔV/ΔP . Those values can be estimated by ultrasound imaging with Doppler blood velocity estimation, by MRI, or invasively. Related properties can also be measured, such as wave propagation time or fractional flow reserve.
  • The vascular system is dynamic, with frequency components and reactive elements. The fundamental frequency is governed by the heart rate delivering a stroke volume forward into the vasculature; a heart rate of 60/minute corresponds to the frequency of 1 Hertz (1 cycle/second). The pressure rise due to the ejection of stroke volume is called the pulse pressure.
  • Numerous factors affect blood flow, including blood composition (affected by anemia or blood dilution), leakiness of vessels, elasticity, wave propagation, streamlines, viscosity, osmotic pressure (affected by protein deficiency and other factors),
  • In a static system, the driving force relates linearly flow by way of resistance (R  in units of dyn·s·cm−5): V=IR (Ohm’s law).
    • Pulmonary:\frac {80 \cdot (mean\ pulmonary\ arterial\ pressure - mean \ pulmonary \ artery \ wedge \ pressure)} {cardiac\ output}
    • Systemic:\frac {80 \cdot (mean\ arterial\ pressure - mean \ right \ atrial \ pressure)} {cardiac\ output}
  • In a dynamic, reactive system, the relation between the driving potential (pressure gradient), and current (blood flow) is governed by a differential equation. However, use of complex numbers and exponentials recovers simplicity similar to Ohm’s law:
    • Variables take the form Ae^{st}, where t is time, s is a complex parameter, and A is a complex scalar. Complex values simply mean two dimensional, e.g., magnitude (as in resistance) plus phase shift (to account for reactive components).
    • Complex version of Ohm’s law: \boldsymbol{V} = \boldsymbol{I} \cdot \boldsymbol{Z} where V and I are the complex scalars in the voltage and current respectively and Z is the complex impedance.
    • Frequency dependent “resistance” is captured by the term impedance.
  • Breathing in increases the return of blood to the heart, adding to pulse variation.
  • Dynamic elastance  (Eadyn relates volume variation (VVS) to pressure variation (PPV): Eadyn=PPV/SVV
    • PPV(%) = 100% × (PPmax − PPmin)/[(PPmax + PPmin)/2)]
      • where PPmax and PPmin are the maximum and minimum pulse pressures determined during a single  respiratory cycle
    • SVV(%) = 100% × [(SVmax − SVmin)/SVmean]
      • where SVmax and SVmin  are the maximum and minimum standard deviation of arterial pressure about the mean arterial pressure during a single respiratory cycle
  • The nervous system provides both stimulants and inhibitors (sympathetic and vagal nerves) to regulate blood vessel wall muscle tone and also heart rate. Many medications, and anesthetic agents in particular, reduce those responses to stimuli, so the vessels dilate, vascular impedance lowers, pressures drop, and autoregulation is impaired.
  • Diuretics aim to decrease volume of circulating fluid, vasodilators aim to increase the vascular space, and elasticity treatments will aim to preserve or improve the ability to accommodate changes in volume of fluid.
    • Vessel dilation near the skin promotes heat loss.
  • Vascular elasticity is impaired by atherosclerosis, menopause, and endothelial dysfunction (impaired nitric oxide signals  response, impaired endothelin response).
  • Elastance in a cyclic pressure system of systole-diastole (contraction-dilation) presents impedance as a pulsatile load on the heart. Inotropy describes the generation of pressure by cardiac contraction, lusiotropy the compliance of the heart to accept filling with minimal back pressure to the lungs. Chronic exposure to elevated vascular impedance leads to impairment of lusiotropy (diastolic failure, stiff heart) and inotropy (systolic failure, weak heart).

2.      Isolated Systolic Hypertension caused by Arterial Stiffening may be inadequately treated by Diuretics or Vasodilatation Antihypertensive Medications

3. Physiology of Circulation and Compensatory Mechanism of Arterial Elasticity

Antihypertensive agents have focused on the following approaches:

  1. The most common prescriptions, a mild diuretic, hydrochlorothiazide (HCTZ), is known to improve blood vessel compliance by reducing cell turgor, which explains why its full onset of benefit as well as its slow offset when stopped can take more than one month.
  2. Chlorthalidone  – Some evidence suggests that chlorthalidone may be superior to hydrochlorothiazide for the treatment of hypertension. However, a recent study concluded: chlorthalidone in older adults was not associated with fewer adverse cardiovascular events or deaths than hydrochlorothiazide. However, it was associated with a greater incidence of electrolyte abnormalities, particularly hypokalemia.
  • Increased vascular space (vasodilation)

    • Alternatively, the pressure can be lowered by increasing the vascular space for a given vascular volume. Examples of mediators for arterial tone (degree of dilation) include nitric oxide, prostacyclin and endothelin.




Hyperpolarization mediated (Calcium channel blocker) Changes in the resting membrane potential of thecell affects the level of intracellular calciumthrough modulation of voltage sensitive calcium channelsin the plasma membrane.
cAMP mediated Adrenergic stimulation results in elevated levelsof cAMP and protein kinase A, which results inincreasing calcium removal from the cytoplasm.
cGMP mediated (Nitrovasodilator) Through stimulation of protein kinase G.Until 2002, the enzyme for this conversion wasdiscovered to be mitochondrial aldehyde dehydrogenase.Proc. Natl. Acad. Sci. USA 102 (34): 12159–12164. doi:10.1073/pnas.0503723102



Hyperpolarization mediated (Calcium channel blocker) adenosineamlodipine (Norvasc),diltiazem (Cardizem,Dilacor XR) andnifedipine (Adalat, Procardia).
cAMP mediated prostacyclin
cGMP mediated (Nitrovasodilator) nitric oxide
  • Reduced pulsatile force (beta blockers)

These work by blocking certain nerve and hormonal signals to the heart and blood vessels, thus lowering blood pressure. Frequently prescribed beta blockers include

  • metoprolol (Lopressor, Toprol XL)
  • carvedilol (Coreg)
  • nadolol (Corgard)
  • penbutolol (Levatol).
  • Metabolized nebivolol increases vascular NO production, involves endothelial ß2-adrenergic receptor ligation, with a subsequent rise in endothelial free [Ca2+]i and endothelial NO synthase–dependent NO production
  • Angiotensin-converting enzyme (ACE) inhibitors

These allow blood vessels to widen by preventing the hormone angiotensin from affecting blood vessels. Frequently prescribed ACE inhibitors include captopril (Capoten), lisinopril (Prinivil, Zestril) and ramipril (Altace).

  • Angiotensin II receptor blockers

These help blood vessels relax by blocking the action of angiotensin. Frequently prescribed angiotensin II receptor blockers include losartan (Cozaar), olmesartan (Benicar) and valsartan (Diovan).
Another very commonly prescribed drug class of medication counteracts hardening of arteries.

Atheroma lipids have enzyme systems that explicitly disassemble cholesterol esters and reconstruct them inside blood vessel walls,e.g.,  Anacetrapib, Genetic variants that improve cholesterol levels are stimulating development of additional medications.

We can propose that atheroma build up in arterial blood vessel walls constitutes a maladaptive defense against aneurysm and risk of vessel rupture from hypertension.

Arguably, HMG-CoA reductase inhibitors,  statin therapy is a second example of a medication that helps protect vascular elasticity, both by its lipid effects and its anti-inflammatory effects.

The best-selling statin is atorvastatin, marketed as Lipitor (manufactured by Pfizer) and Torvast. By 2003, atorvastatin became the best-selling pharmaceutical in history,[4] with Pfizer reporting sales of US$12.4 billion in 2008.[5] As of 2010, a number of statinsare on the market: atorvastatin (Lipitor and Torvast), fluvastatin (Lescol), lovastatin (Mevacor, Altocor, Altoprev), pitavastatin(Livalo, Pitava), pravastatin (Pravachol, Selektine, Lipostat), rosuvastatin (Crestor) and simvastatin (Zocor, Lipex).[6] Several combination preparations of a statin and another agent, such as ezetimibe/simvastatin, are also available.

References for Statins from:

Clinical Considerations of Statin Therapy’s manifold effects, in

Compensatory Effects in the Physiology of Circulation

Before declaring vessel elasticity a new and highly desirable treatment target, consider that it is not firmly established that hardening of arteries (loss of elasticity) is entirely maladaptive.

In parallel with any focus on increasing vascular elasticity or compliance, each of the issues discussed, below merits scrutiny and investigation.

Cardiac Circulation Dynamics

Endothelium morphology, rheological properties of intra vasculature fluid dynamics and blood viscosity provided explanation for shear stress of vessels under arterial pressure


Aging and Vasculature Diminished Elasticity

While among other reasons for Hypertension increasing prevalence with aging, arterial stiffening is one.

Yet, stiffer vessels are more efficient at transmitting pressure to distal targets. With aging, muscle mass diminishes markedly and the contribution to circulation from skeletal muscle tissue compressions combined with competent venous valves fades.



Aging and Myocardial Diminished Contractility and Ejection Fraction

With aging heart contractility diminishes. These issues can cause under perfusion of tissues, inadequate nutrient blood delivery (ischemia), lactic acidosis, tissue dysfunction and multi-organ failure. Hardened arteries may compensate. Thus, pharmacotherapy to increase Arterial Elasticity may be counterindicated for patients with mild to progressive CHF.


Our biosystems are highly interdependent, and we cannot leap to conclusions without careful thorough evidence. Increasing arterial elastance will lower vascular impedance and change the frequency components of our pulsatile perfusion system.

MOST comprehensive review of the Human Cardiac Conduction System presented to date:

Diminished contractility will increase the amount of energy needed to maintain circulation. It will change efficiency dramatically – consider the difference between periodically pushing someone sitting on a swing at the resonance frequency if the pendulum versus significantly off resonance.


Increased Arterial Elasticity – Potential Risk to Myocardium

The hypothesis that we should focus on cellular therapies to increase vascular compliance may decrease the circulation efficiency and result in worsening of cardiac right ventricular morphology and development of Dilated cardiomyopathy and hypertrophic cardiomyopathy (muscle thickening and diastolic failure), an undesirable outcome resulting from an attempt to treat the hypertension.

4. Vascular Compliance – The Potential of Noval Therapies

  • Novel Mechanism for Disease Etiology for the Cardiac Phenotype: Modulation of Nuclear and Cytoskeletal Actin Polymerization.

Lamin A/C and emerin regulate MKL1–SRF activity by modulating actin dynamics

Chin Yee Ho,

Diana E. Jaalouk,

Maria K. Vartiainen

Jan Lammerding

Nature (2013) doi:10.1038/nature12105

Published online 05 May 2013


Cornell University, Weill Institute for Cell and Molecular Biology/Department of Biomedical Engineering, Ithaca, New York 14853, USA

Chin Yee Ho &

Jan Lammerding

Brigham and Women’s Hospital/Harvard Medical School, Department of Medicine, Boston 02115, Massachusetts, USA

Chin Yee Ho,

Diana E. Jaalouk &

Jan Lammerding

Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland

Maria K. Vartiainen

Present address: American University of Beirut, Department of Biology, Beirut 1107 2020, Lebanon.

Diana E. Jaalouk


C.Y.H., D.E.J. and J.L. conceived and designed the overall project, with valuable help from M.K.V. C.Y.H. and D.E.J. performed the experiments. C.Y.H., D.E.J. and J.L. analysed data. C.Y.H. and J.L. wrote the paper.

Corresponding author Jan Lammerding

Laminopathies, caused by mutations in the LMNA gene encoding the nuclear envelope proteins lamins A and C, represent a diverse group of diseases that include Emery–Dreifuss muscular dystrophy (EDMD), dilated cardiomyopathy (DCM), limb-girdle muscular dystrophy, and Hutchison–Gilford progeria syndrome1. Most LMNA mutations affect skeletal and cardiac muscle by mechanisms that remain incompletely understood. Loss of structural function and altered interaction of mutant lamins with (tissue-specific) transcription factors have been proposed to explain the tissue-specific phenotypes1. Here we report in mice that lamin-A/C-deficient (Lmna/) and LmnaN195K/N195K mutant cells have impaired nuclear translocation and downstream signalling of the mechanosensitive transcription factor megakaryoblastic leukaemia 1 (MKL1), a myocardin family member that is pivotal in cardiac development and function2. Altered nucleo-cytoplasmic shuttling of MKL1 was caused by altered actin dynamics in Lmna/ and LmnaN195K/N195K mutant cells. Ectopic expression of the nuclear envelope protein emerin, which is mislocalized in Lmnamutant cells and also linked to EDMD and DCM, restored MKL1 nuclear translocation and rescued actin dynamics in mutant cells. These findings present a novel mechanism that could provide insight into the disease aetiology for the cardiac phenotype in many laminopathies, whereby lamin A/C and emerin regulate gene expression through modulation of nuclear and cytoskeletal actin polymerization.

  • Genetic Therapy to Conductivity Disease

  • Regenerative Medicine for Vasculature Function Protection



5. Stabilizing BP Variability is the next Big Target in Hypertension Management

Hypertension caused by Arterial Stiffening is Ineffectively Treated by Diuretics and Vasodilatation Antihypertensives

Barcelona, Spain – An aging population grappling with rising rates of hypertension and other cardiometabolic risk factors should prompt an overhaul of how hypertension is diagnosed and monitored and should spur development of drugs with entirely new mechanisms of action, one expert says. Speaking here at the 2013 International Conference on Prehypertension and Cardiometabolic Syndrome, meeting cochair Dr Reuven Zimlichman (Tel Aviv University, Israel) argued that the definitions of hypertension, as well as the risk-factor tables used to guide treatment, are no longer appropriate for a growing number of patients.

Most antihypertensives today work by producing vasodilation or decreasing blood volume and so are ineffective treatments in ISH patients. In the future, he predicts, “we will have to start looking for a totally different medication that will aim to improve or at least to stabilize arterial elasticity: medication that might affect factors that determine the stiffness of the arteries, like collagen, like fibroblasts. Those are not the aim of any group of antihypertensive medications today.”

Zimlichman believes existing databases could be used to develop algorithms that take this progression of disease into account, in order to better guide hypertension management. He also points out that new ambulatory blood-pressure-monitoring devices also measure arterial elasticity. “Unquestionably, these will improve our ability to diagnose both the status of the arteries and the changes of the arteries with time as a result of our treatment. So if we treat the patient and we see no improvement in arterial elasticity, or the patient is worse, something is wrong, something is not working—either the patient is not taking the medication, or our choice of medication is not appropriate, or the dose is insufficient, etc.”

Oslo, Norway – New research that is only just starting to be digested by the hypertension community indicates that visit-to-visit variability in blood-pressure readings will likely become another way of looking for “at-risk” hypertensive patients and in fact is likely to be more reliable as an indicator of cardiovascular risk than the currently used mean BP.

The Goal of Stabilizing BP variability 

June 29, 2010  

Discussing the importance of this issue for guidelines and clinical practice, Dr Tony Heagerty (University of Manchester, UK) told the recent European Society of Hypertension (ESH) European Meeting on Hypertension 2010: “We are poking around in the dark, offering treatment blankly across a large community, and probably treating a lot of people who don’t need to be treated, while not necessarily treating the highest-risk patients. We should stop being reassured by ‘occasional’ normal BPs. The whole game now is, can we improve the identification of our ‘at-risk’ individuals?”

Heagerty was speaking at a special plenary session on late-breaking research discussing BP variability as a risk factor. This issue has emerged following new analyses reported at the ACC meeting and published in a number of papers in the Lancet and Lancet Neurology earlier this year, which showed that variability in blood pressure is a much stronger determinant of both stroke and coronary disease outcome than average blood pressure.

Three years later, 2/1/2013, Zimlichman also argued that definitions of essential and secondary hypertension have changed very little over the past few decades and have typically only been tweaked up or down related to other CV risk factors. Diastolic hypertension has been the primary goal of treatment, and treatment goals have not adequately taken patient age into account (in whom arterial stiffening plays a larger role), and they have typically relied too heavily on threshold cutoffs, rather than the “linear progression” of risk factors and their impact on organ damage.

6. Mathematical Modeling: Arterial stiffening provides sufficient explanation for primary hypertension

Klas H. PettersenScott M. BugenhagenJavaid NaumanDaniel A. BeardStig W. Omholt

(Submitted on 3 May 2013 (v1), last revised 6 May 2013 (this version, v2))

Hypertension is one of the most common age-related chronic diseases and by predisposing individuals for heart failure, stroke and kidney disease, it is a major source of morbidity and mortality. Its etiology remains enigmatic despite intense research efforts over many decades. By use of empirically well-constrained computer models describing the coupled function of the baroreceptor reflex and mechanics of the circulatory system, we demonstrate quantitatively that arterial stiffening seems sufficient to explain age-related emergence of hypertension. Specifically, the empirically observed chronic changes in pulse pressure with age, and the impaired capacity of hypertensive individuals to regulate short-term changes in blood pressure, arise as emergent properties of the integrated system. Results are consistent with available experimental data from chemical and surgical manipulation of the cardio-vascular system. In contrast to widely held opinions, the results suggest that primary hypertension can be attributed to a mechanogenic etiology without challenging current conceptions of renal and sympathetic nervous system function. The results support the view that a major target for treating chronic hypertension in the elderly is the reestablishment of a proper baroreflex response.

Klas H. Pettersen1, Scott M. Bugenhagen2, Javaid Nauman3, Daniel A. Beard2 & Stig W. Omholt3

1Department of Mathematical and Technological Sciences, Norwegian University of Life Science, Norway

2Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA

3NTNU Norwegian University of Science and Technology, Department of Circulation and Medical Imaging, Cardiac Exercise Research Group, Trondheim, Norway

Correspondence should be addressed to: KHP (

Keywords: hypertension, mechanogenic, baroreceptor signaling, cardiovascular model, arterial stiffening

Author contributions: K.H.P. and S.W.O. designed the study. K.H.P. constructed the

integrated model and performed the numerical experiments with contributions from

D.A.B. and S.M.B.. J.N. extracted and compiled empirical test data from the HUNT2

Survey. S.W.O, K.H.P. and D.A.B. wrote the paper.


7. Classification of Blood Pressure and Hypertensive Treatment:

Best Practice of Care in the US

8. Genetic Risk for High Blood Pressure

Hypertension.2013; 61: 931doi: 10.1161/​HYP.0b013e31829399b2

Blood Pressure Single-Nucleotide Polymorphisms and Coronary Artery Sisease (page 995)

Blood pressure (BP) is considered a major cardiovascular risk factor that is influenced by multiple genetic and environmental factors. However, the precise genetic underpinning influencing interindividual BP variation is not well characterized; and it is unclear whether BP-associated genetic variants also predispose to clinically apparent cardiovascular disease. Such an association of BP-related variants with cardiovascular disease would strengthen the concept of BP as a causal risk factor for cardiovascular disease. In this issue of Hypertension, analyses within the Coronary ARtery DIsease Genome-Wide Replication And Meta-Analysis consortium indicate that common genetic variants associated with BP in the population, indeed, contribute to the susceptibility for coronary artery disease (CAD). Lieb et al tested 30 single-nucleotide polymorphisms—that based on prior studies were known to affect BP—for their association with CAD. In total, data from 22 233 CAD cases and 64 762 controls were analyzed. The vast majority (88%) of BP-related single-nucleotide polymorphisms were also shown to increase the risk of CAD (as defined by an odds ratio for CAD >1; Figure). On average, each of the multiple BP-raising alleles was associated with a 3% (95% confidence interval, 1.8%–4.3%) risk increase for CAD.

Masked Hypertension in Diabetes Mellitus (page 964)

The first important finding in the IDACO study of masked hypertension (MH) in the population with diabetes mellitus and non–diabetes mellitus was that antihypertensive treatment converted some sustained hypertensives into sustained normotensives; this resulted in an increased cardiovascular disease risk in the treated versus untreated normotensive comparator group (Figure). Not surprisingly, normalization of blood pressure (BP) with treatment did not eliminate the lifetime cardiovascular disease burden associated with prior elevated BP nor did it correct other cardiometabolic risk factors that clustered with the hypertensive state.

The second important IDACO finding was that treatment increased the prevalence of MH by decreasing conventional BP versus daytime ambulatory BP (ABP) by a ratio of ≈3 to 2. The clinical implication of increased prevalence of MH with therapy in the population of both diabetes mellitus and non–diabetes mellitus was that these subjects did not receive sufficient antihypertensive therapy to convert MH into normalized ABP (ie, treated, normalized ABP being the gold standard for minimizing cardiovascular disease risk). Indeed, there is a transformation-continuum from sustained hypertension to MH and finally to sustained normotension with increasing antihypertensive therapy. These IDACO findings strongly suggest that many physicians mistakenly have their primary focus on normalizing in-office rather than out-of-office home BP and/or 24-hour ABP values and this results in an increased prevalence of MH. However, what constitutes optimal normalized ABP will remain empirical until established in randomized controlled trials.

Genetic Risk Score for Blood Pressure (page 987)

Elevated blood pressure (BP) is a strong, independent, and modifiable risk factor for stroke and heart disease. BP is a heritable trait, and genome-wide association studies have identified several genetic loci that are associated with systolic BP, diastolic BP, or both. Although the variants have modest effects on BP, typically 0.5 to 1.0 mm Hg, their presence may act over the entire life course and, therefore, lead to substantial increase in risk of cardiovascular disease (CVD). However, the independent impact of these variants on CVD risk has not been established in a prospective setting. Havulinna et al genotyped 32 common single-nucleotide polymorphisms in several Finnish cohorts, with up to 32 669 individuals after exclusion of prevalent CVD cases. The median follow-up was 9.8 years, during which 2295 incident CVD events occurred. Genetic risk scores were created for systolic BP and diastolic BP by multiplying the risk allele count of each single-nucleotide polymorphism by the effect size estimated in published genome-wide association studies on BP traits. The GRSs were strongly associated with baseline systolic BP, diastolic BP, and hypertension (all P<10–62). Hazard ratios for incident CVD increased roughly linearly by quintile of systolic BP or diastolic BP GRS (Figure). GRSs remained significant predictors of CVD risk after adjustment for traditional risk factors, even including BP and use of antihypertensive medication. These findings are consistent with a lifelong effect of these variants on BP and CVD risk.

Related Articles on Genetics and Blood Pressure

Genetic Predisposition to Higher Blood Pressure Increases Coronary Artery Disease Risk

  • Wolfgang Lieb,
  • Henning Jansen,
  • Christina Loley,
  • Michael J. Pencina,
  • Christopher P. Nelson,
  • Christopher Newton-Cheh,
  • Sekar Kathiresan,
  • Muredach P. Reilly,
  • Themistocles L. Assimes,
  • Eric Boerwinkle,
  • Alistair S. Hall,
  • Christian Hengstenberg,
  • Reijo Laaksonen,
  • Ruth McPherson,
  • Unnur Thorsteinsdottir,
  • Andreas Ziegler,
  • Annette Peters,
  • John R. Thompson,
  • Inke R. König,
  • Jeanette Erdmann,
  • Nilesh J. Samani,
  • Ramachandran S. Vasan,
  • andHeribert Schunkert
  • , on behalf of CARDIoGRAM

Hypertension. 2013;61:995-1001, published online before print March 11 2013,doi:10.1161/HYPERTENSIONAHA.111.00275

Masked Hypertension in Diabetes Mellitus: Treatment Implications for Clinical Practice

  • Stanley S. Franklin,
  • Lutgarde Thijs,
  • Yan Li,
  • Tine W. Hansen,
  • José Boggia,
  • Yanping Liu,
  • Kei Asayama,
  • Kristina Björklund-Bodegård,
  • Takayoshi Ohkubo,
  • Jørgen Jeppesen,
  • Christian Torp-Pedersen,
  • Eamon Dolan,
  • Tatiana Kuznetsova,
  • Katarzyna Stolarz-Skrzypek,
  • Valérie Tikhonoff,
  • Sofia Malyutina,
  • Edoardo Casiglia,
  • Yuri Nikitin,
  • Lars Lind,
  • Edgardo Sandoya,
  • Kalina Kawecka-Jaszcz,
  • Jan Filipovský,
  • Yutaka Imai,
  • Jiguang Wang,
  • Hans Ibsen,
  • Eoin O’Brien,
  • and Jan A. Staessen
  • , on behalf of the International Database on Ambulatory blood pressure in relation to Cardiovascular Outcomes (IDACO) Investigators

Hypertension. 2013;61:964-971, published online before print March 11 2013,doi:10.1161/HYPERTENSIONAHA.111.00289

A Blood Pressure Genetic Risk Score Is a Significant Predictor of Incident Cardiovascular Events in 32 669 Individuals

  • Aki S. Havulinna,
  • Johannes Kettunen,
  • Olavi Ukkola,
  • Clive Osmond,
  • Johan G. Eriksson,
  • Y. Antero Kesäniemi,
  • Antti Jula,
  • Leena Peltonen,
  • Kimmo Kontula,
  • Veikko Salomaa,
  • and Christopher Newton-Cheh

Hypertension. 2013;61:987-994, published online before print March 18 2013,doi:10.1161/HYPERTENSIONAHA.111.00649

9. Is it Hypertension or Physical Inactivity: Cardiovascular Risk and Mortality – New results in 3/2013.

Heart doi:10.1136/heartjnl-2012-303461

  • Epidemiology
  • Original article

Estimating the effect of long-term physical activity on cardiovascular disease and mortality: evidence from the Framingham Heart Study

  1. Susan M Shortreed1,2,
  2. Anna Peeters1,3,
  3. Andrew B Forbes1

+Author Affiliations

  1. 1Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia

  2. 2Biostatistics Unit, Group Health Research Institute, Seattle, Washington, USA

  3. 3Obesity and Population Health Unit, Baker IDI Heart and Diabetes Institute, Melbourne, Australia

Correspondence toDr Susan M Shortreed, Biostatistics Unit, Group Health Research Institute, 1730 Minor Avenue, Suite 1600, Seattle, WA 98101, USA;

  • Published Online First 8 March 2013


Objective In the majority of studies, the effect of physical activity (PA) on cardiovascular disease (CVD) and mortality is estimated at a single time point. The impact of long-term PA is likely to differ. Our study objective was to estimate the effect of long-term adult-life PA compared with long-term inactivity on the risk of incident CVD, all-cause mortality and CVD-attributable mortality.

Design Observational cohort study.

Setting Framingham, MA, USA.

Patients 4729 Framingham Heart Study participants who were alive and CVD-free in 1956.

Exposures PA was measured at three visits over 30 years along with a variety of risk factors for CVD. Cumulative PA was defined as long-term active versus long-term inactive.

Main outcome measures Incident CVD, all-cause mortality and CVD-attributable mortality.

Results During 40 years of follow-up there were 2594 cases of incident CVD, 1313 CVD-attributable deaths and 3521 deaths. Compared with long-term physical inactivity, the rate ratio of long-term PA was 0.95 (95% CI 0.84 to 1.07) for CVD, 0.81 (0.71 to 0.93) for all-cause mortality and 0.83 (0.72 to 0.97) for CVD-attributable mortality. Assessment of effect modification by sex suggests greater protective effect of long-term PA on CVD incidence (p value for interaction=0.004) in men (0.79 (0.66 to 0.93)) than in women (1.15 (0.97 to 1.37)).


  • Cumulative long-term PA has a protective effect on incidence of all-cause and CVD-attributable mortality compared with long-term physical inactivity.
  • In men, but not women, long-term PA also appears to have a protective effect on incidence of CVD.

Summary – PENDING

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44. Smith H (2011) in Texts in Applied Mathematics, Texts in Applied Mathematics. (Springer New York, New York, NY), pp 119–130.

Other related articles were published on this Open Access Online Scientific Journal including the following:

Pearlman, JD and A. Lev-Ari 5/24/2013 Imaging Biomarker for Arterial Stiffness: Pathways in Pharmacotherapy for Hypertension and Hypercholesterolemia Management

Lev-Ari, A. 5/17/2013 Synthetic Biology: On Advanced Genome Interpretation for Gene Variants and Pathways: What is the Genetic Base of Atherosclerosis and Loss of Arterial Elasticity with Aging

Bernstein, HL and A. Lev-Ari 5/15/2013 Diagnosis of Cardiovascular Disease, Treatment and Prevention: Current & Predicted Cost of Care and the Promise of Individualized Medicine Using Clinical Decision Support Systems

Pearlman, JD and A. Lev-Ari 5/7/2013 On Devices and On Algorithms: Arrhythmia after Cardiac Surgery Prediction and ECG Prediction of Paroxysmal Atrial Fibrillation Onset

Pearlman, JD and A. Lev-Ari 5/4/2013 Cardiovascular Diseases: Decision Support Systems for Disease Management Decision Making

Larry H Bernstein, MD, FACP, 12/10/2012

Genomics & Genetics of Cardiovascular DiseaseDiagnoses: A Literature Survey of AHA’s Circulation Cardiovascular Genetics, 3/2010 – 3/2013

Aviva Lev-Ari, PhD, RN and Larry H. Bernstein, MD, FACP, 3/7/2013

Mitochondrial Dysfunction and Cardiac Disorders

Curator: Larry H Bernstein, MD, FACP

Aviva Lev-Ari, PhD, RN, 4/7/2013


Read Full Post »

Biomaterials Technology: Models of Tissue Engineering for Reperfusion and Implantable Devices for Revascularization

Author and Curator: Larry H Bernstein, MD, FACP


Curator: Aviva Lev-Ari, PhD, RN

This is the THIRD of a three part series on the evolution of vascular biology and the studies of the effects of biomaterials
in vascular reconstruction and on drug delivery, which has embraced a collaboration of cardiologists at Harvard Medical School , Affiliated Hospitals, and MIT,
requiring cardiovascular scientists at the PhD and MD level, physicists, and computational biologists working in concert, and
an exploration of the depth of the contributions by a distinguished physician, scientist, and thinker.

The FIRST part – Vascular Biology and Disease – covered the advances in the research on

Drug Eluting Stents: On MIT’s Edelman Lab’s Contributions to Vascular Biology and its Pioneering Research on DES

  • vascular biology,
  • signaling pathways,
  • drug diffusion across the endothelium and
  • the interactions with the underlying muscularis (media),
  • with additional considerations for type 2 diabetes mellitus.

The SECOND part – Stents and Drug Delivery – covered the

Vascular Repair: Stents and Biologically Active Implants

  • purposes,
  • properties and
  • evolution of stent technology with
  • the acquired knowledge of the pharmacodynamics of drug interactions and drug distribution.

In this THIRD part, on Problems and Promise of Biomaterials Technology, we cover the biomaterials used and the design of the cardiovascular devices, extension of uses, and opportunities for improvement

Biomaterials Technology: Tissue Engineering and Vascular Models –

Problems and Promise

We have thus far elaborated on developments in the last 15 years that have led to significant improvements in cardiovascular health.

First, there has been development of smaller sized catheters that can be introduced into

  • not only coronary arteries, but into the carotid and peripheral vasculature;

Second, there has been specific design of coated-stents that can be placed into an artery

  • for delivery of a therapeutic drug.

This began with a focus on restenosis, a serious problem after vascular repair, beginning
with the difficult problem of  control of heparin activity given intravenously, and was
extended to modifying the heparan-sulfate molecular structure

  • to diminish vascular endothelial hyperplasia,
  • concurrent with restriction of the anticoagulant activity.

Third, the ability to place stents with medicated biomaterials locally has extended to

  • the realm of chemotherapy, and we shall see where this progresses.

The Engineered Arterial Blood Flow Models

Biomedical engineers, in collaboration with physicians, biologists, chemists, physicists, and
mathematicians, have developed models to predict vascular repair by knowledge of

  • the impact of interventions on blood flow.

These models have become increasingly sophisticated and precise, and they propel us
toward optimization of cardiovascular therapeutics in general and personalizing treatments
for patients with cardiovascular disease. (1)
The science of vascular biology has been primarily stimulated by the clinical imperative to

  • combat complications that ensue from vascular interventions.

Thus, when a novel vascular biological finding or cardiovascular medical/surgical technique
is presented, we are required to ask the 2-fold question:

  • what have we learned about the biology of the blood vessel?
  • how might this knowledge be used to enhance clinical perspective and treatment?

The innovative method of engineering arterial conduits presented by Campbell et al. in
Circulation Research presents us with just such a challenge, and we deal with it’s biological and clinical ramifications.

Each of four pivotal studies in vascular tissue engineering has been an important advance
in the progression to a tissue-engineered blood vessel that can serve as a

  • living graft, responsive to the biological environment as
  • a self-renewing tissue with an inherent healing potential.
  • Weinberg and Bell taught us that a tissue-engineered graft could be constructed
  • and could be composed of human cells.

L’heureux et al demonstrated that the mechanical strength of such a material

  • derived in major part from the extracellular matrix and
  • production of matrix and integrity of cellular sheets
  • could be enhanced by alterations in culture conditions.

Niklason et al. noted that grafts are optimally formed

  • when incubated within environmental conditions that they will confront in vivo
  • or would have experienced if formed naturally.

Campbell et al. now demonstrate that it is possible to remove

  • the immune reaction and acute rejection that may follow cell-based grafting
  • by culturing tissues in the anticipated host and
  • address a fundamental issue of whether cell source or site of cell placement
  • dictates function after cell implantation.

It appears that the vascular matrix can be remodeled by the body according to the needs of the environment. It may
very well be that the ultimate configuration of autologous cell-based vascular graft need not be determined at
outset by the cells that comprise the device, but rather

  • by a dynamics that is established by environmental needs, wherein the body molds
  • tissue-engineered constructs to meet
    • local flow,
    • metabolic, and
    • inflammatory requirements.

In other words, cell source for tissue reconstruction may be secondary to
cell pliability to environmental influence.

Endothelial and smooth muscle cells from many, perhaps any,

  • vascular bed can be used to create new grafts and will then
  • achieve secondary function once in place in the artery.

The environmental remodeling observed after implantation

  • may modify limitations of grafts that are composed of nonvascular peritoneal cells whose initial structure
    is not either venous or arterial. (2)
  • The trilaminate vascular architecture provides biochemical regulation and mechanical integrity.
  • Yet regulatory control can be regained after injury without recapitulating tertiary structure.

Tissue-engineered (TE) endothelium controls repair even when

  • placed in the perivascular space of injured vessels.

It remains unclear from vascular repair studies whether endothelial implants recapitulate the vascular
epithelial lining
or expose injured tissues to endothelial cells (ECs) with unique healing potential because

  • ECs line the vascular epithelium and the vasa vasorum.

Authors examined this issue in a nonvascular tubular system, asking whether airway repair is controlled by

  • bronchial epithelial cells (EPs) or by
  • Endothelial Cells (ECs) of the perfusing bronchial vasculature.

Localized bronchial denuding injury

  • damaged epithelium, narrowed bronchial lumen, and led to
  • mesenchymal cell hyperplasia, hypervascularity, and inflammatory
  • cell infiltration. Peribronchial TE constructs embedded with

EPs or ECs limited airway injury, although optimum repair was obtained

  • when both cells were present in TE matrices.

EC and EP expression of

  • PGE2, TGF1, TGF2, GM-CSF, IL-8, MCP-1, and soluble VCAM-1
  • and ICAM-1 was altered by matrix embedding,

but expression was altered most significantly when both,

  • EC and EP,  cells were present simultaneously.

EPs may provide for functional control of organ injury and fibrous response, and

ECs may provide for preservation of tissue perfusion and the epithelium in particular.

Together the two cells

  • optimize functional restoration and healing, suggesting that
  • multiple cells of a tissue contribute to the differentiated biochemical function and repair
    of a tissue, but 
    need not assume
  • a fixed, ordered architectural relationship, as in intact tissues, to achieve these effects. (3)

Matrix-embedded Endothelial Cells (MEECs) Implants

The implantation of matrix-embedded endothelial cells (MEECs)

  • is considered to have therapeutic potential in controlling the vascular response to injury and
  • maintaining patency in arteriovenous anastomoses.

Authors considered the 3-dimensional microarchitecture of the tissue engineering scaffold to be
a key regulator of endothelial behavior in MEEC constructs.

Notably, Authors found that

  • ECs in porous collagen scaffold had a markedly altered cytoskeletal structure with oriented actin
    and rearranged focal adhesion proteins, in comparison to cells grown on 2D surfaces.

Examining the immunomodulatory capabilities of MEECs revealed, MEECs were able to reduce the recruitment
of monocytes
to an inflamed endothelial monolayer by 5-fold compared to EC on 2D surfaces.

An analysis of secreted factors from the cells revealed

  • an 8-fold lower release of Monocyte Chemotactic Protein-1 (MCP-1) from MEECs.

Differences between 3D and 2D cultured cells were abolished in the presence of

  • inhibitors to the focal adhesion associated signaling molecule Src, suggesting that
  • adhesion-mediated signaling is essential in controlling the potent immunomodulatory
    effects of MEEC. (4)

Cardiogenesis is regulated by a complex interplay between transcription factors. How do these interactions
regulate the transition from mesodermal precursors to cardiac progenitor cells (CPCs)?

Yin Yang 1 (YY1), a member of the GLI-Kruppel

  • family of DNA-binding zinc finger transcription factor (TF), can
  • activate or inhibit transcription in a context-dependent manner.

Bioinformatic-based Transcription Factor Genome-wide Sequencing Analysis

These investigators performed a bioinformatic-based transcription factor genome-wide sequencing analysis

  • binding  site analysis on upstream promoter regions of genes that are enriched in embryonic stem cell–derived CPCs
  • to identify novel regulators of mesodermal cardiac lineage

From 32 candidate transcription factors screened, they found that

  • Yin Yang 1 (YY1), a repressor of sarcomeric gene expression, is present in CPCs.

They uncovered the ability of YY1 to transcriptionally activate Nkx2.5,

  • Nkx2.5 as a key marker of early cardiogenic commitment.
  • YY1 regulates Nkx2.5 expression via a 2.1-kb cardiac-specific enhancer as demonstrated by in vitro
  1. luciferase-based assays,
  2. in vivo chromatin immunoprecipitation,
  3. and genome-wide sequencing analysis.

Furthermore, the ability of YY1 to activate Nkx2.5 expression depends on its cooperative interaction with Gata4.

Cardiac mesoderm–specific loss-of-function of YY1 resulted in early embryonic lethality.

This was corroborated in vitro by embryonic stem cell–based assays which showed the

  • overexpression of YY1 enhanced the cardiogenic differentiation of embryonic stem cells into CPCs.

The results indicate an essential and unexpected role for YY1

  • to promote cardiogenesis as a transcriptional activator of Nkx2.5
  • and other CPC-enriched genes. (5)

Proportional Hazards Models to Analyze First-onset of Major
Cardiovascular Disease Events

Various measures of arterial stiffness and wave reflection are considered to be cardiovascular risk markers.

Prior studies have not assessed relations of a comprehensive panel of stiffness measures to prognosis

Authors used Proportional Hazards Models to analyze first-onset of major cardiovascular disease events 

  • myocardial infarction,
  • unstable angina,
  • heart failure, or
  • stroke

In relation to arterial stiffness measured by

  • pulse wave velocity [PWV]
  • wave reflection
  • augmentation index [AI]
  • carotid-brachial pressure amplification [PPA]
  • and central pulse pressure [CPP]

in 2232 participants (mean age, 63 years; 58% women) in the Framingham Heart Study.

During median follow-up of 7.8 (range, 0.2 to 8.9) years,

  • 151 of 2232 participants (6.8%) experienced an event.

In multivariable models adjusted for

  • age,
  • sex,
  • systolic blood pressure,
  • use of antihypertensive therapy,
  • total and high-density lipoprotein cholesterol concentrations,
  • smoking, and
  • presence of diabetes mellitus,

Higher aortic PWV was associated with a 48% increase in

  • cardiovascular disease risk
    (95% confidence interval, 1.16 to 1.91 per SD; P0.002).

After PWV was added to a standard risk factor model,

  • integrated discrimination improvement was 0.7%
    (95% confidence interval, 0.05% to 1.3%; P < 0.05).

In contrast, AI, CPP, and PPA were not related to

  • cardiovascular disease outcomes in multivariable models.

(1) Higher aortic stiffness assessed by PWV is associated with

  • increased risk for a first cardiovascular event.

(2) Aortic PWV improves risk prediction when added to standard risk factors

  • and may represent a valuable biomarker of CVD risk in the community. (6)

1. Engineered arterial models to correlate blood flow to tissue biological response. J Martorell, P Santoma, JJ Molins,
AA Garcıa-Granada, JA Bea, et al.  Ann NY Acad Sci 2012: 1254:51–56. (Issue: Evolving Challenges in Promoting
Cardiovascular Health)

2.  Vascular Tissue Engineering. Designer Arteries. Elazer R. Edelman. Circ Res. 1999; 85:1115-1117

3.  Tissue-engineered endothelial and epithelial implants differentially and synergistically regulate airway repair.
BG Zani, K Kojima, CA Vacanti, and ER Edelman.   PNAS 13, 2008; 105(19):7046–7051.

4.  The role of scaffold microarchitecture in engineering endothelial cell immunomodulation.
L Indolfi, AB Baker, ER Edelman. Biomaterials 2012;

5.  Essential and Unexpected Role of Yin Yang 1 to Promote Mesodermal Cardiac Differentiation. S Gregoire, R Karra,
D Passer, Marcus-André Deutsch, et al.  Circ Res. 2013;112:900-910.

6.  Arterial Stiffness and Cardiovascular Events. The Framingham Heart Study.
GF Mitchell, Shih-Jen Hwang, RS Vasan, MG Larson, et al.  Circulation. 2010;121:505-511.

Cardiology Diagnosis of ACS and Stents – 2012

The Year in Cardiology 2012: Acute Coronary Syndromes.

Nick E.J. West

The European Society of Cardiology (ESC) produced updated guidance on management of STEMI in 2012.
It also produced a third version of the Universal Definition of Myocardial Infarction.
The importance of early diagnosis is stressed, with first ECG in patients

  • with suspected STEMI recommended within 10 min of first medical contact (FMC)
  • and primary percutaneous coronary intervention (PPCI) for STEMI
  • ideally within 90 min (rated ‘acceptable’ out to a maximum of 120 min).

The guidance highlights the importance of collaborative networks

  • to facilitate achievement of such targets.
  • the importance of prompt assessment
  • management of atypical presentations not always considered under the umbrella of STEMI, including
    • left bundle branch block (LBBB),
    • paced rhythms, and
    • isolated ST-segment elevation in lead aVR,

especially when accompanied by symptoms consistent with myocardial ischaemia.

Therapeutic hypothermia is now recommended for

  • all resuscitated patients with STEMI complicated by cardiac arrest
  •  immediate coronary angiography with a view to follow-on PPCI
  • when the ECG demonstrates persistent ST-segment elevation.

In the light of recently published studies and meta-analyses,

  • including that of Kalesan et al., drug-eluting stents (DES) are
  • now routinely preferred to bare metal stents (BMS) in view of
  • the reduced need for repeat revascularization and the lack of
  • previously perceived hazard for stent thrombosis.

The more potent antiplatelet agents prasugrel and ticagrelor are also preferred

  • to clopidogrel for all STEMI cases, with duration of dual antiplatelet therapy (DAPT)
  • ideally for 1 year, but reduced to a strict
  • minimum of 6 months for patients receiving DES.

The Third Universal Definition of Myocardial Infarction was published
simultaneously with the STEMI guidance. This guideline endorses

  • cardiac troponin as the biomarker of choice to detect myocardial necrosis
  • with spontaneously occurring myocardial infarction (MI) defined as an
  • elevation above the 99th percentile upper reference value for the assay.

There is further development and clarification of MI in different settings

  • to allow standardization across trials and registries

in particular after revascularization procedures: after CABG with normal baseline troponin

  • MI is defined as a rise to a value 10 times greater than baseline in the first 48 h, and
  • a rise to 5 times greater than 99th percentile upper reference after PCI

in patients with a normal baseline level (or a 20% rise when troponin is elevated and stable or falling pre-procedure).

ACCF/AHA  updated guidance on the management of unstable angina/non-STEMI:

angiography with a view to revascularization

  • is now recommended within 12–24 h of presentation, with
  • DAPT pre-loading prior to PCI procedures also now advocated.

Ticagrelor and prasugrel are cited as acceptable alternatives to clopidogrel.
The maintenance dose of aspirin recommended for the majority of cases is 81 mg daily.
This guideline brings about transatlantic agreement in most areas.

Risk Stratification

Identification and appropriate triage of patients presenting to emergency departments
with acute chest pain remains a difficult dilemma:

  • many are low-risk and have a non-cardiac origin
  • a significant minority with coronary artery disease may not be picked up
    on clinical grounds even when accompanied by appropriate tests,

    • including ECG and biomarker estimation used in conjunction
    • with a clinical risk score (e.g. GRACE, TIMI).

As endorsed in ESC guidance, there has been increasing interest in

  • non-typical ECG patterns for the diagnosis of STEMI; although LBBB is
  • an accepted surrogate

Widimsky et al.  retrospectively analysed 6742 patients admitted to hospital with acute MI

  • in patients presenting with right bundle branch block, a blocked epicardial vessel was
  • more common (51.7 vs. 39.4%; P < 0.001) and incidence of both shock and mortality
  • comparable with LBBB (14.3 vs. 13.1%; P = NS; and 15.8 vs. 15.4%; P = NS, respectively).

Wong et al. demonstrated the importance of ST-elevation in lead aVR,

  • often viewed as indicative of left main stem occlusion, having increased mortality
  • in patients presenting with both inferior and anterior infarction.

Perhaps the most important data regarding the ECG in 2012 were also the most simple:

  • Antoni et al. highlighted a powerful and very simple method of risk stratification;
  •  heart rate measured on a 12-lead ECG at discharge after Primary PCI (PPCI) is an
  • independent predictor of mortality at 1 and 4 years of follow-up.

Patients with a discharge heart rate of ≥70 b.p.m. had a two-fold higher mortality at both follow-up
time points, with every increase of 5 b.p.m. in heart rate

  • equating to a 29% increase in mortality at 1 year and 24% at 5 years.

These findings have important implications for the optimization of patient therapies after MI (including the use of
rate-limiting agents such as beta-blockers, calcium channel-blockers, and ivabradine), although large randomized
trials are needed to confirm that

  • interventions to reduce heart rate will replicate the benefits observed in this study.

Figure 1.  Kaplan–Meier time-to-event plots for heart rate at discharge divided by quartiles and all-cause mortality
(A and C) and cardiovascular mortality (B and D) at 1-year (A and B) and 4-year (C and D) follow-up,
demonstrating relationship between discharge heart rate and mortality after PPCI for STEMI.
Modified from Antoni et al.

Coronary Intervention and Cardioprotection in Acute Coronary Syndromes

Microvascular obstruction during PCI for ACS/STEMI is associated with increased infarct size and adverse prognosis;
its pathophysiology is thought to be a combination of

  • mechanical distal embolization of thrombus and plaque constituents during PCI,  coupled with
  • enhanced constriction/hyperreactivity of the distal vascular bed.

The most novel Strategy to Reduce Infarct Size

is the use of a Bare Metal Stent (BMS) covered on its outer surface with a mesh micronet designed to
trap and hold potentially friable material that might embolize distally at the time of PCI.

The MASTER study randomized 433 STEMI patients to PPCI

  • with conventional BMS or DES at the operator’s discretion vs.
  • the novel MGuard stent (InspireMD, Tel Aviv, Israel);

the primary endpoint of complete ST-segment resolution was better

  • in patients receiving MGuard (57.85 vs. 44.7%; P = 0.008), as was
  • the achievement of TIMI grade 3 flow in the treated vessel (91.7 vs. 82.9%; P = 0.006).

Nevertheless, median ST-segment resolution did not differ

  • between treatment groups,
  • myocardial blush grade was no different, and
  • safety outcomes at 30 days (death, adverse events) as well as
  • overall MRI-determined infarct mass.

Higher TVR rates may accrue with a BMS platform when compared with

  • current-generation DES (as now endorsed for PPCI in ESC guidance).

In comparing the four studies in cardioprotection, there remains little to choose between strategies as evidenced by

  • the relatively minor differences between surrogate endpoints employed regardless of
  • therapeutic intervention chosen (Figure 2).

Figure 2.  Comparison of study endpoints for reduction in infarct size in STEMI.
Study endpoints listed on the x-axis. STR, ST-segment resolution; TIMI 3, thrombolysis in
myocardial infarction grade 3 antegrade flow; myocardial blush grade 2/3 (MBG 2/3).

Recent advances in

  • PCI equipment,
  • peri-procedural pharmacology,
  • technique, and safety, as well as
  • convergence of national guidance,

are leading to the point where

  • even in the highest risk patients such as those presenting with ACS, small improvements
  • may be difficult to discern despite large well-designed and -conducted studies.


  1. a. The Task Force on the management of ST-segment elevation acute myocardial infarction
    of the European Society of Cardiology. ESC guidelines for the management of acute
    myocardial infarction in patients presenting with ST-segment elevation. Eur Heart J
    2012;33:2569–2619.  b. Management of acute myocardial infarction in patients presenting
    with ST-segment elevation. The Task Force on the Management of Acute Myocardial
    Infarction of the European Society of Cardiology.  Eur Heart J 2003; 24 (1): 28-66.
  2. ESC Guidelines for the management of acute coronary syndromes in patients presenting
    without persistent ST-segment elevation: The Task Force for the management of acute
    coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation
    of the European Society of Cardiology (ESC).
  3. Thygesen K, Alpert JS, Jaffe AS, Simoons ML, Chaitman BS, White HD. The Writing Group on
    behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Universal Definition of
    Myocardial Infarction. Third universal definition of myocardial infarction.
    Eur Heart J 2012;33:2551–2567.
  4. Kalesan B, Pilgrim T, Heinimann K, Raber L, Stefanini GG, et al. Comparison of drug-eluting
    stents with bare metal stents in patients with ST-segment elevation myocardial infarction.
    Eur Heart 2012;33:977–987.
  5. Jneid H, Anderson JL, Wright RS, Adams CS, et al. 2012 ACCF/AHA Focused Update of the
    Guideline for the Management of Patients with Unstable Angina/Non-ST-Elevation Myocardial
    Infraction (Updating the 2007 Guideline and Replacing the 2011 Focused Update). A Report
    of the American College of CardiologyFoundation/American Heart Association Task Force
    on Practice Guidelines. J Am Coll Cardiol 2012;60:645–681.
  6. Widimsky P, Rohác F, Stásek J, Kala P, Rokyta R, et al. Primary angioplasty in acute myocardial
    infarction with right bundle branch block: should new onset right bundle branch block be added
    to future guidelines as an indication for reperfusion therapy? Eur HeartJ 2012;33:86–95.
  7. Wong CK, Gao W, Stewart RA, French JK, and the HERO-2 Investigators. The prognostic meaning of
    the full spectrum of aVR ST-segment changes in acute myocardial infarction.
    Eur Heart J 2012;33:384–392.
  8. Antoni L, Boden H, Delgado V, Boersma E, et al. Relationship between discharge heart rate and mortality
    in patients after myocardial infarction treated with primary percutaneous coronary intervention.
    Eur Heart J 2012;33:96–102.
  9. Stone GW, Abizaid A, Silber S, Dizon JM, Merkely B, et al. Prospective, randomised, multicenter evaluation
    of a polyethylene terephthalate micronet mesh-covered stent (MGuard) in ST-segment elevation myocardial
    infarction. The MASTER Trial. J Am Coll Cardiol. doi:pii:S0735-1097(12)04506-8. 10.1016/j.jacc.2012.09.004. 
  10. Zhou C, Yao Y, Zheng Z, Gong J, Wang W, Hu S, Li L. Stenting technique, gender, and age are associated with
    cardioprotection by ischaemic postconditioning in primary coronary intervention: a systematic review of
    10 randomized trials. Eur Heart J 2012;33:3070–3077.

Resistant Hypertension.

Robert M. Carey.
Hypertension. 2013;61:746-750.

Resistant hypertension is defined as failure to achieve goal blood pressure (BP) <140/90 mm Hg
(or <130/80 mm Hg in patients with diabetes mellitus or chronic kidney disease) in patients with

  • hypertension who are compliant with maximum tolerated doses of an appropriate antihypertensive drug regimen consisting of a minimum of 3 agents of different classes, including a diuretic.
  • Patients who meet the criteria for resistant hypertension but whose BP can be controlled on maximum tolerated
    doses of ≥4 antihypertensive agents are classified as having controlled resistant hypertension.

Although the number of failed antihypertensive drugs required for the classification of resistant hypertension is arbitrary,

  • this diagnosis identifies patients at high risk for having a potentially curable form of hypertension, and
  • those who may benefit from specific therapeutic approaches to lower BP.


The first portion of this document shows the impact that ER Edelman and his peers have had in the development
of interventional cardiology, and in carrying out studies to test, validate, or reject assumptions about the interaction of
biomaterials with

  • vascular and smooth muscle tissue in the repair of injured vessels, by
  1. trauma
  2. inflammatory injury
  3. stent placement.

In the second portion of this discussion, I introduce current views about complications in implanted devices, evolving
standards, and the current definitions of stable, unstable, and previously unclassified ACS risk.

Pushing Drug-Eluting Stents Into Uncharted Territory

Simpler Than You Think—More Complex Than You Imagine

Campbell Rogers, MD; Elazer R. Edelman, MD, PhD.  Circulation 2006; 113: 2262-2265.​CIRCULATIONAHA.106.623470

Mechanical failure is a characteristic of a material or a device and not necessarily an indication of inadequacy. All devices
will fail under some specific stress. It is only failure at the lowest levels of stress that may represent inadequacy. Stress on
a material, for example, rises with strain until a critical load is exceeded, at which point the material fatigues and loses
mechanical integrity. Failure analysis, the science by which these conditions are rigorously defined, is an important
component of device design, development, and use. Once the transition point to failure is identified, material use can be
restricted to the zone of safety or modified so as to have this zone expanded. Just as the characterization of a material is
incomplete unless pushed to the limits of load bearing, characterization of an implantable device is incomplete unlesspreclinical and clinical environments test the limits of device functionality. It was in this light in 1999 that the Authors noted the impossibility of defining the functional limits of novel bare metal stents in head-to-head trials, which, by necessity, could only include lesions into which the predicate device (the Palmaz-Schatz stent, Cordis, Warren, NJ) could have be placed.

New School Percutaneous Interventions

Over the past 5 years, the number of percutaneous interventions has grown by 40%. This expansion derives from an
increased breadth of cases, as percutaneous interventions are now routinely performed in diabetic, small-vessel, multilesion,diffuse disease, and acute coronary syndrome settings. Contemporaneously, widespread adoption of drug-eluting stents has emboldened clinicians and provided greater security in the use of these devices in lesions or patients previously thought to

Head-to-head randomized trial data have accumulated so that analysis may demonstrate differences among drug-eluting stents. The playing field for prospective randomized trials could enhance the weight of evidence to unanswered questions about what underlying factors determine device failure.

Complexity Simplified

Drug-eluting stent “failure” can be defined operationally in the same way as material failure:

  • inadequate function in the setting of a given load or strain.

The inability to withstand stress may take many forms that can change over time. Failure may be manifest acutely as

  • the inability to deliver a stent to the desired location,
  • subacutely as stent thrombosis or
  • postprocedural myonecrosis, and later as
  • restenosis

“Simple lesions” are those in which few devices should fail;“Complex” lesions have a heightened risk of failure. To be of value, each scale of advancing complexity must provoke higher failure rates.  For any device may fail sooner than another along one such “complexity” scale and later along another. As advanced drug-eluting stent designs have enhanced deliverability and reduced restenosis rates, 7 randomized trials comparing directly the two Food and Drug Administration (FDA)-approved drug-eluting stents, Cypher (Cordis-Johnson and Johnson) and Taxus (Boston Scientific, Boston, Mass), have been reported.  These trials report a broad range of restenotic failure as evidenced by the need for revascularization. Across these trials, driven by a variety of factors, revascularization rates vary quite widely.

The clinical end point of target lesion revascularization (TLR) becomes

  • a single measure of device failure.

When the 7 trials are depicted in order of increasing TLR, the rate of failure increases more slowly with 1 device than
the other.  This gives two regression plots for Taxus vs Cypher with different slopes, as complexity increases, and the

  • separation between the failure rates of the two devices broadens plotted against “degree of complexity” assigned by the  slopes of the lines.

Finally, the correlation between TLR rates for Taxus and Cypher stents indicates that trial-specific events and conditions determined TLR (with a sharp slope of Taxus vs Cypher (r-sq = 0.85).  The ratio of TLR (the slope) wasgreater than 3, suggesting that although both devices are subject to increasing failure as complexity increases,

  • one device becomes ever-more likely than the other to fail when applied in settings with ever-higher TLR risk.

In other words, composite medical devices with a wide range of

  • structural,
  • geometric, and
  • pharmacological differences
    • can be shown to produce different clinical effects
    • as the environments in which they are tested become increasingly complex.

What the Individual Trials Cannot Tell Us

The progressive difference between the performances of the 2 FDA-approved drug-eluting stents as they are pushed into
more complex settings is precisely what one would anticipate from medical devices with different performance signatures.
Most randomized trials, even if they include high complexity, are unable to identify predictors of failure because of the low numbers of patients enrolled, and the problem gets worse as the number of subsets increase. Consequently, device development, and clinical practice, knowing which patient or lesion characteristics confer higher failure rates is critical.
This analysis has centered on restenosis. Other failure modes to be considered are

  • stent thrombosis,
  • postprocedural myonecrosis
  • late plaque rupture
  • vascular disease away from the site
  • heightened inflammatory reaction
    • are no less critical and may be determined by
    • completely different device or patient characteristics.

Well-executed registry or pooled data

It is in this light that the registry report of Kastrati et al. in the current issue of Circulation is of greatest value. There are
two ways in which well-executed registry or pooled data can be most complementary to randomized trials.

First, large numbers of patients provide a higher incidence of rare failure modes as well as allow more granular determination of lesion- or patient-specific predictors of failure (meta-analysis or better, combined data file). A pooled analysis of several head-to-head randomized bare metal stent trials allowed identification of clear risk factors for stent thrombosis that had eluded analysis of the individual (smaller) trials.

Second, registry or pooled data may incorporate a broader range of patient characteristics, allowing greater discrimination between devices. The report of Kastrati et al may fall into this category as well, as it includes “high risk” populations from several randomized trials. They report on more than 2000 lesions in 1845 patients treated with either Taxus or Cypher drug-eluting stents at two hospitals.  The study population is from a series of randomized trials comparing Taxus and Cypher stents.   Using multivariate analysis to identify what lesion and patient characteristics predict failure (restenosis), they identified risk factors that included

  • prior history of coronary bypass surgery
  • calcification
  • smaller vessel size
  • greater degree of prestent and poststent stenosis.

Use of a Cypher rather than Taxus stent was independently associated with lower restenosis risk.

An interesting negative finding was the absence of diabetes as a significant predictor, at odds with strong suggestions from several other analyses. A better understanding from preclinical or clinical studies of the effect of diabetic states on restenosis is critical.

Author’s opinion voiced:

This Author (LHB), considers the study underpowered to answer that question because of further partitioning with several variables. Pooled data with

  • rigorous ascertainment and
  • careful statistical methodology, taken
  • together with randomized trial data, open a door to device choice based on the knowledge that risk of failure (complexity) does vary, and
  • the higher the complexity, the greater the incremental benefit of choosing one device over another.

A decision algorithm is therefore possible, whereby multiple failure modes and risk factors are weighed, and

  • an optimum stent choice made which balances
  • safety and efficacy based on the totality of evidence, rather than anecdote and loose comparisons of disparate subgroups from individual trials.

Evaluating Clinical Trials

The subject of trial(s) is difficult… the aim and meaning of all the trials… is

  • to let people know what they ought to do or what they must believe

It was perhaps naïve to imagine that devices as different one from another as the two current FDA-approved drug-eluting
stents would produce identical clinical results. If so, it ought not to come as a surprise that head-to-head randomized trial
data from many different countries in complex settings are now indicating just how differently the 2 devices may perform.

Future trials should be designed and evaluated to examine why these differences exist. Trials residing
only in previous safety and complexity domains

  • are unlikely to offer deeper insights into
    1. device performance,
    2. patient care decisions, or
    3. discrimination of alternative therapies.

We look forward to more trials that will examine what we currently believe to be the limits of

  • drug-eluting stents and interventional cardiology and to

help define in simple terms differences

  • between complex devices applied to complex problems.

This 2009 article was an excellent demonstration of comparing two commonly used coated-stents, and then extending the argument to the need for more data to further delineated the factors that explain the differences they found. In the previous article, the SECOND in the three article series,  Stents and Drug Delivery

Vascular Repair: Stents and Biologically Active Implants

we concentrated on stents and drug delivery, and not on stent failure.  But the following article in J Control Release,

was published the following year, and is another example of this method of explanatory approach to the problem.

Lesion Complexity Determines Arterial Drug Distribution After Local Drug Delivery

AR Tzafriri,  N Vukmirovic, VB Kolachalama, I Astafieva, ER Edelman. J Control Release. 2010; 142(3): 332–338.
http://:dx.       PMCID: PMC2994187

Local drug delivery from endovascular stents has transformed how we treat coronary artery disease. Yet, few drugs are in fact effective when delivered from endovascular implants and those that possess a narrow therapeutic window. The width of this window is predicated to a great degree upon the extent of drug deposition and distribution through the arterial wall.

  • Drugs that are retained within the blood vessel are far more effective than those that are not.

Thus, for example, heparin regulates virtually every aspect of the vascular response to injury, but it is so soluble and diffusible that it simply cannot stay in the artery for more than minutes after release.

  • Heparin has no effect on intimal hyperplasia when eluted from a stent.
  • Paclitaxel and sirolimus in contradistinction are far smaller compounds with perhaps more narrow and specific effects than heparin.

These drugs bind tenaciously to tissue protein elements and specific intracellular targets and remain beneath stent struts long after release.

The clinical efficacy of paclitaxel and sirolimus at reducing coronary artery restenosis rates following elution from stents appears incontrovertible. Emerging clinical and preclinical data suggest that the benefit of the local release of these drugs is beset by significant complications, that rise with lesion complexity as

  • the native composition and layered ultrastructure of the native artery is more significantly disrupted.

Virmani and others have hypothesized that the attraction of lipophilic drugs like paclitaxel and sirolimus to fat should affect their retention within and effects upon atheromatous lesions.

Though stents are deployed in diseased arteries drug distribution has only been quantified in intact, non-diseased vessels.

Authors @ MIT, correlated steady-state arterial drug distribution with tissue ultrastructure and composition in abdominal aortae from atherosclerotic human autopsy specimens and rabbits

  • with lesions induced by dietary manipulation and controlled injury.

Drug and compositional metrics were quantified and correlated at a compartmental level, in each of the tunica layers, or at an intra-compartmental level. All images were processed to

  • eliminate backgrounds and artifacts, and
  • pixel values between thresholds were extracted for all zones of interest.

Specific algorithms analyzed each of the histo/immuno-stained arterial structures. Intra-compartmental analyses were

  • performed by sub-dividing arterial cross-sections into 2–64 equal sectors and
  • evaluating the pixel-average luminosity for each sector.

Linear regression of drug versus compositional luminosities asymptotically approached steady state after subdivision into 16 sectors. This system controlled delivered dose and removed the significant unpredictability in release that is imposed by variability

  • in stent position relative to the arterial wall,
  • inflation techniques and stent geometry.
As steady state tissue distribution results were obtained under constant source conditions, without washout by flowing blood,
  • they constitute upper bounds for arterial drug distribution
  • following transient modes of in vivo drug delivery wherein
  • only a fraction of the eluted dose is absorbed by the artery

Paclitaxel, everolimus, and sirolimus deposition in human aortae was maximal in the media and scaled inversely with lipid content.

Net tissue paclitaxel and everolimus levels were indistinguishable in mildly injured rabbit arteries independent of diet. Yet, serial sectioning of cryopreserved arterial segments demonstrated

  • a differential transmural deposition pattern that was amplified with disease and
  • correlated with expression of their intracellular targets, tubulin and FKBP-12.

Tubulin distribution and paclitaxel binding increased with

  • vascular injury and macrophage infiltration, and
  • were reduced with (reduced) lipid content.

Sirolimus analogues and their specific binding target FKBP-12 were less sensitive to alterations of diet
in mildly injured arteries, presumably reflecting a faster transient response of FKBP-12 to injury.

The idea that drug deposition after balloon inflation and stent implantation within diseased, atheromatous and sclerotic vessels tracks so precisely with specific tissue elements is

  • an important consideration of drug-eluting technologies and
  • may well require that we consider diseased rather than naïve tissues in preclinical evaluations.

Another publication in the same year reveals the immense analytical power used in understanding the complexities
of drug-eluting stents.

Luminal Flow Amplifies Stent-Based Drug Deposition in Arterial Bifurcations

Kolachalama VB, Levine EG, Edelman ER.    PLoS ONE 2009; 4(12): e8105.

Treatment of arterial bifurcation lesions using drug-eluting stents (DES) is now common clinical practice.
Arterial drug distribution patterns become challenging to analyze if the lesion involves more than a vessel
such as in the case of bifurcations.  As use extends to nonstraightforward lesions and complex geometries,
questions abound

  • regarding DES longevity and safety

Indeed, there is no consensus on best stent placement scenario, no understanding as to

  • whether DES will behave in bifurcations as they do in straight segments, and
  • whether drug from a main-branch (MB) stent can be deposited within a side-branch (SB).

It is not evident how to

  • efficiently determine the efficacy of local drug delivery and
  • quantify zones of excessive drug that are
  • harbingers of vascular toxicity and thrombosis,
  • and areas of depletion that are associated
  • with tissue overgrowth and
  • luminal re-narrowing.

Geometry modeling and governing equations

Authors @MIT constructed two-phase computational models of stent-deployed arterial bifurcations

  • simulating blood flow and drug transport to investigate the
  • factors modulating drug distribution when the main-branch (MB) was treated using a DES.

The framework for constructing physiologically realistic three dimensional computational models of single
and bifurcated arterial vessels was SolidWorks (Dassault Systemes) (Figs. 1A–1B, Movie S1). The geometry
generation algorithm allowed for controlled alteration of several parameters including

  • stent location
  • strut dimensions
  • stent-cell shape
  • lumen diameter to arterial tissue thickness ratio
  • lengths of the arterial branches
  • extent of stent apposition and
  • the bifurcation angle.

For the current study, equal lengths (2LS) were assumed for the proximal and distal sections of the MB from the bifurcation. The SB was constructed at an angle of 300. The inlet conditions were based on

  • mean blood flow and
  • diameter measurements

obtained from human left anterior descending coronary artery (LAD).

The diameter of the lumen (DMB) and thickness (TMB) for the MB were defined such that DMB=TMB~10 and

  • this ratio was also maintained for the SB.

Schematics of the computational models used for the study. A stent of length LS is placed at the upstream section of the arterial vessel in the (A) absence and in the (B) presence of a bifurcation, respectively.

  • Insets in (B) denote delta wing stent design (i),
  • strut thickness (d) (ii), and
  • the outlets of the side-branch in (iii) and
  • and the main-branch in (iv).

A delta wing-shaped cell design belonging to the class of slotted-tube stents was used for all simulations.
The length (LS) and diameter (DS) were

  • fixed at 9|10-2 m and 3|10-2 m, respectively, for the MB stent.

All stents were assumed to be perfectly apposed to the lumen of MB and the intrinsic strut shape was modeled as

  • square with length 10-4 m.

The continuity and momentum equations were solved within the arterial lumen, where

vf , rho~1060 kg=m3, P and m are

  • velocity
  • density
  • pressure and the
  • viscosity of blood.

In order to capture boundary layer effects at the lumen-wall (or mural) surface, a Carreau model was employed for

  • all the simulations to account for shear thinning behavior of blood at low shear rates

In the arterial lumen, drug transport followed advection-diffusion process.  Similar to the momentum transport in the arterial lumen, the continuity equation was solved within the arterial wall by assuming it as a porous medium.

A finite volume solver (Fluent, ANSYS Inc.) was utilized to perform the coupled flow and drug transport simulations. The semi-implicit method for pressure-linked equations-consistent (SIMPLEC) algorithm was used with second order spatial accuracy. A second order discretization scheme was used to solve the pressure equation and second order  upwind schemes were used for the momentum and concentration variables.

Simulations for each case were performed

  • for at least 2500 iterations or
  • until there was a 1028 reduction in the mass transport residual.

Drug distribution in non-bifurcating vessels

Constant flow simulations generate local recirculation zones juxtaposed to the stent which in turn act as

  • secondary sources of drug deposition and
  • induce an asymmetric tissue drug distribution profile in the longitudinal flow direction.

Our3D computational model predicts a far more extensive fluid mechanic effect on drug deposition than previously appreciated in two-dimensional (2D) domains.

Within the stented region, drug deposition on the mural interface quantified as

  • the area-weighted average drug concentration (AWAC)
  • in the distal segment of the stent is 12% higher than the proximal segment

Total drug uptake in the arterial wall denote as volume-weighted average concentration (VWAC) is highest in the middle segment of the stent and 5% higher than the proximal stent region

Increased mural drug deposition along the flow direction in a non-bifurcating arterial vessel.

Inset shows a high magnification image of drug pattern in the distal stent segment outlined by black dashed line.
The entire stent is divided into three equal sections denoted as proximal, middle and distal sections, respectively
and the same notation is followed for subsequent analyses.

These observations indicate that the flow-mediated effect induced by the presence of the stent in the artery

  • is maximal on the mural surface and
  • increases in the longitudinal flow direction.

Further, these results suggest that transmural diffusion-mediated transport sequesters drug from both

  • the proximal and distal portions of the stent
  • into the central segment of the arterial wall beneath the stent.

Predicted levels of average drug concentration varied exponentially

  • with linear increments of inlet flow rate

but maintained similar relationship between the inter-segment concentration levels within the stented region.

Stent position influences drug distribution in bifurcated beds

The location of the stent directly modulates

  • the extent to which drug is deposited on the arterial wall as well as
  • spatial gradients that are established in arterial drug distribution.

Similar to the non-bifurcating vessel case,

  • peaks in drug deposition occur directly beneath the stent struts regardless of the relative location of the SB with respect to the stent. However,
  • drug distribution and corresponding spatial heterogeneity within inter-strut regions depend on the stent location with respect to the flow divider.
  • Mural drug deposition is a function of relative stent position with respect to the side-branch and Reynolds number in arterial bifurcations.

Impact of flow on drug distribution in bifurcations

One can appreciate how blood flow and flow dividers affect arterial drug deposition, and especially on inter-strut drug deposition.

  • Drug deposition within the stented-region of MB  and the entire SB significantly decreases with flow acceleration regardless of stent placement.

Simulations predicted

Local endovascular drug delivery was long assumed to be governed by diffusion alone. The impact of flow was
thought to be restricted to systemic dilution.

  • 2D computational models suggested a complex interplay between the stent and blood flow
  1. Arterial drug deposition is a function of stent location.
  2. Arterial drug deposition is mediated by flow in bifurcated beds.
  • extensive flow-mediated drug delivery in bifurcated vascular beds where the drug distribution patterns are heterogeneous and sensitive to relative stent position and luminal flow.

A single DES in the MB coupled with large retrograde luminal flow on the lateral wall of the side-branch (SB) can provide drug deposition on the SB lumen-wall interface, except

  • when the MB stent is downstream of the SB flow divider.
  • the presence of the SB affects drug distribution in the stented MB.

Fluid mechanic effects play an even greater role than in the SB

  • especially when the DES is across and downstream to the flow divider
  • and in a manner dependent upon

    the Reynolds number.


We presented the hemodynamic effects on drug distribution patterns using a

  • simplified uniform-cell stent design, though our methodology is adaptable to
    several types of stents with variable design features.

Variability in arterial drug distribution due to other geometric and morphologic aspects such as

  • bifurcation angle, arterial taper as well as presence of a trifurcation can also be understood using our computational framework.

Further, performance of a candidate DES using other commonly used stenting procedures for bifurcation lesions such as culotte and crush techniques can be quantified based on their resulting drug distribution patterns.

Other Related Articles that were published on this Open Access Online Scientific Journal include the following:

Vascular Repair: Stents and Biologically Active Implants

Larry H Bernstein, MD, FACP and Aviva Lev-Ari, RN, PhD, 5/4/2013

Modeling Targeted Therapy

Larry H Bernstein, MD, FACP 3/2/2013

Quantum Biology And Computational Medicine

Larry H Bernstein, MD, FACP 4/3/2013

Virtual Biopsy – is it possible?

Larry H Bernstein, MD, FACP 3/3/2013

Reprogramming cell fate  3/2/2013

Larry H Bernstein, MD, FACP

How Methionine Imbalance with Sulfur-Insufficiency Leads to Hyperhomocysteinemia

Larry H Bernstein, MD, FACP 4/4/2013

Amyloidosis with Cardiomyopathy

Larry H Bernstein, MD, FACP 3/31/2013

Nitric Oxide, Platelets, Endothelium and Hemostasis

Larry H Bernstein, MD, FACP 11/8/2012

Mitochondrial Damage and Repair under Oxidative Stress

Larry H Bernstein, MD, FACP 10/28/2012

Endothelial Function and Cardiovascular Disease

Larry H Bernstein, MD, FACP 10/25/2012

Endothelial Dysfunction, Diminished Availability of cEPCs, Increasing CVD Risk for Macrovascular Disease –Therapeutic Potential of cEPCs

Aviva Lev-Ari, PhD, RN 8/27/2012

Prostacyclin and Nitric Oxide: Adventures in Vascular Biology – A Tale of Two Mediators

Aviva Lev-Ari, RN, PhD, 4/30/2013

Genetics of Conduction Disease: Atrioventricular (AV) Conduction Disease (block): Gene Mutations – Transcription, Excitability, and Energy Homeostasis

Aviva Lev-Ari, PhD, 4/28/2013

Revascularization: PCI, Prior History of PCI vs CABG

Aviva Lev-Ari, PhD, 4/25/2013

Revascularization: PCI, Prior History of PCI vs CABG

Aviva Lev-Ari, PhD, RN 4/25/2013

Cholesteryl Ester Transfer Protein (CETP) Inhibitor: Potential of Anacetrapib to treat Atherosclerosis and CAD

Aviva Lev-Ari, PhD, RN 4/7/2013

Hypertriglyceridemia concurrent Hyperlipidemia: Vertical Density Gradient Ultracentrifugation a Better Test to Prevent Undertreatment of High-Risk Cardiac Patients

Aviva Lev-Ari, PhD, RN 4/4/2013

Fight against Atherosclerotic Cardiovascular Disease: A Biologics not a Small Molecule – Recombinant Human lecithin-cholesterol acyltransferase (rhLCAT) attracted AstraZeneca to acquire AlphaCore

Aviva Lev-Ari, PhD, RN 4/3/2013

High-Density Lipoprotein (HDL): An Independent Predictor of Endothelial Function & Atherosclerosis, A Modulator, An Agonist, A Biomarker for Cardiovascular Risk

Aviva Lev-Ari, PhD, RN 3/31/2013

Acute Chest Pain/ER Admission: Three Emerging Alternatives to Angiography and PCI

Aviva Lev-Ari, PhD, RN 3/10/2013

Genomics & Genetics of Cardiovascular Disease Diagnoses: A Literature Survey of AHA’s Circulation Cardiovascular Genetics, 3/2010 – 3/2013

Lev-Ari, A. and L H Bernstein 3/7/2013

The Heart: Vasculature Protection – A Concept-based Pharmacological Therapy including THYMOSIN

Aviva Lev-Ari, PhD, RN 2/28/2013

Arteriogenesis and Cardiac Repair: Two Biomaterials – Injectable Thymosin beta4 and Myocardial Matrix Hydrogel

Aviva Lev-Ari, PhD, RN 2/27/2013

Coronary artery disease in symptomatic patients referred for coronary angiography: Predicted by Serum Protein Profiles

Aviva Lev-Ari, PhD, RN 12/29/2012

Special Considerations in Blood Lipoproteins, Viscosity, Assessment and Treatment

Bernstein, HL and Lev-Ari, A. 11/28/2012

Peroxisome proliferator-activated receptor (PPAR-gamma) Receptors Activation: PPARγ transrepression for Angiogenesis in Cardiovascular Disease and PPARγ transactivation for Treatment of Diabetes

Aviva Lev-Ari, PhD, RN 11/13/2012γ-transrepression-for-angiogenesis-in-cardiovascular-disease-and-pparγ-transactivation-for-treatment-of-dia/

Clinical Trials Results for Endothelin System: Pathophysiological role in Chronic Heart Failure, Acute Coronary Syndromes and MI – Marker of Disease Severity or Genetic Determination?

Aviva Lev-Ari, PhD, RN 10/19/2012

Endothelin Receptors in Cardiovascular Diseases: The Role of eNOS Stimulation

Aviva Lev-Ari, PhD, RN 10/4/2012

Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography

Aviva Lev-Ari, PhD, RN 10/4/2012

Positioning a Therapeutic Concept for Endogenous Augmentation of cEPCs — Therapeutic Indications for Macrovascular Disease: Coronary, Cerebrovascular and Peripheral

Aviva Lev-Ari, PhD, RN 8/29/2012

Cardiovascular Outcomes: Function of circulating Endothelial Progenitor Cells (cEPCs): Exploring Pharmaco-therapy targeted at Endogenous Augmentation of cEPCs

Aviva Lev-Ari, PhD, RN 8/28/2012

Endothelial Dysfunction, Diminished Availability of cEPCs, Increasing CVD Risk for Macrovascular Disease – Therapeutic Potential of cEPCs

Aviva Lev-Ari, PhD, R N 8/27/2012

Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs

Aviva Lev-Ari, PhD, RN 8/24/2012

Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production

Aviva Lev-Ari, PhD, RN 7/19/2012

Resident-cell-based Therapy in Human Ischaemic Heart Disease: Evolution in the PROMISE of Thymosin beta4 for Cardiac Repair

Aviva Lev-Ari, PhD, RN 4/30/2012

Triple Antihypertensive Combination Therapy Significantly Lowers Blood Pressure in Hard-to-Treat Patients with Hypertension and Diabetes

Aviva Lev-Ari, PhD, RN 5/29/2012

Macrovascular Disease – Therapeutic Potential of cEPCs: Reduction Methods for CV Risk

Aviva Lev-Ari, PhD, RN 7/2/2012

Mitochondria Dysfunction and Cardiovascular Disease – Mitochondria: More than just the “powerhouse of the cell”

Aviva Lev-Ari, PhD, RN 7/9/2012

Bystolic’s generic Nebivolol – positive effect on circulating Endothelial Proginetor Cells endogenous augmentation

Aviva Lev-Ari, PhD, RN 7/16/2012

Arteriogenesis and Cardiac Repair: Two Biomaterials – Injectable Thymosin beta4 and Myocardial Matrix Hydrogel

Aviva Lev-Ari, PhD, RN 2/27/2013

Cardiac Surgery Theatre in China vs. in the US: Cardiac Repair Procedures, Medical Devices in Use, Technology in Hospitals, Surgeons’ Training and Cardiac Disease Severity”

Aviva Lev-Ari, PhD, RN 1/8/2013

Heart Remodeling by Design – Implantable Synchronized Cardiac Assist Device: Abiomed’s Symphony

Aviva Lev-Ari, PhD, RN 7/23/2012

Acute Chest Pain/ER Admission: Three Emerging Alternatives to Angiography and PCI

Aviva Lev-Ari, PhD, RN 3/10/2013

Dilated Cardiomyopathy: Decisions on implantable cardioverter-defibrillators (ICDs) using left ventricular ejection fraction (LVEF) and Midwall Fibrosis: Decisions on Replacement using late gadolinium enhancement cardiovascular MR (LGE-CMR)

Aviva Lev-Ari, PhD, RN 3/10/2013

The Heart: Vasculature Protection – A Concept-based Pharmacological Therapy including THYMOSIN

Aviva Lev-Ari, PhD, RN 2/28/2013

FDA Pending 510(k) for The Latest Cardiovascular Imaging Technology

Aviva Lev-Ari, PhD, RN 1/28/2013

PCI Outcomes, Increased Ischemic Risk associated with Elevated Plasma Fibrinogen not Platelet Reactivity

Aviva Lev-Ari, PhD, RN 1/10/2013

The ACUITY-PCI score: Will it Replace Four Established Risk Scores — TIMI, GRACE, SYNTAX, and Clinical SYNTAX

Aviva Lev-Ari, PhD, RN 1/3/2013

Coronary artery disease in symptomatic patients referred for coronary angiography: Predicted by Serum Protein Profiles

Aviva Lev-Ari, PhD, RN 12/29/2012

Heart Renewal by pre-existing Cardiomyocytes: Source of New Heart Cell Growth Discovered

Aviva Lev-Ari, PhD, RN 12/23/2012

Cardiovascular Risk Inflammatory Marker: Risk Assessment for Coronary Heart Disease and Ischemic Stroke – Atherosclerosis.

Aviva Lev-Ari, PhD, RN 10/30/2012

To Stent or Not? A Critical Decision

Aviva Lev-Ari, PhD, RN 10/23/2012

New Definition of MI Unveiled, Fractional Flow Reserve (FFR)CT for Tagging Ischemia

Aviva Lev-Ari, PhD, RN 8/27/2012

Ethical Considerations in Studying Drug Safety — The Institute of Medicine Report

Aviva Lev-Ari, PhD, RN 8/23/2012

New Drug-Eluting Stent Works Well in STEMI

Aviva Lev-Ari, PhD, RN 8/22/2012

Expected New Trends in Cardiology and Cardiovascular Medical Devices

Aviva Lev-Ari, PhD, RN 8/17/2012

Coronary Artery Disease – Medical Devices Solutions: From First-In-Man Stent Implantation, via Medical Ethical Dilemmas to Drug Eluting Stents

Aviva Lev-Ari, PhD, RN 8/13/2012

Percutaneous Endocardial Ablation of Scar-Related Ventricular Tachycardia

Aviva Lev-Ari, PhD, RN 7/18/2012

Competition in the Ecosystem of Medical Devices in Cardiac and Vascular Repair: Heart Valves, Stents, Catheterization Tools and Kits for Open Heart and Minimally Invasive Surgery (MIS)

Aviva Lev-Ari, PhD, RN 6/22/2012

Global Supplier Strategy for Market Penetration & Partnership Options (Niche Suppliers vs. National Leaders) in the Massachusetts Cardiology & Vascular Surgery Tools and Devices Market for Cardiac Operating Rooms and Angioplasty Suites

Aviva Lev-Ari, PhD, RN 6/22/2012

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Author and Reporter: Anamika Sarkar, Ph.D.

Among many important roles of Nitric oxide (NO), one of the key actions is to act as a vasodilator and maintain cardiovascular health. Induction of NO is regulated by signals in tissue as well as endothelium.

Importance of NO has been nicely reviewed in the article  “Discovery of NO and its effects of vascular biology”. Other articles which are good readings for the importance of NO are  – a) regulation of glycolysis b) NO in cardiovascular disease c) NO and Immune responses Part I and Part II d) NO signaling pathways (Also, please see Source for more articles on NO and its significance).

The rate of production of NO has been established to be dependent on Wall Shear Stress (WSS) (Mashour and Broock, Brain Res., 1999) . Many mathematical models have been developed as 2D diffusion models to predict distribution of NO transport in single vessels, eg. arterioles (Please see Sources for references ).

Chen et. al. (Med. Biol. Eng. Comp., 2011) developed a 3-D model consisting of two branched arterioles and nine capillaries surrounding the vessels. Their model not only takes into account of the 3-D volume, but also branching effects on blood flow (Please see Fig 1 and Fig 2 from Chen et. al. 2011 ).


Fig. 1 Blood phase separation with vascular branching. RBC
fractional flow in daughter branch alpha is not necessarily equal
to that in branch beta


The mathematical model considers dynamic characteristics related to blood flow, blood vessel structures and transport mechanism in the wall. The authors have considered effects of branching and ratio of diameters between blood vessels of parent and children to determine the fractional blood flow which gets distributed in the network. These branching effects of the vessels will also affect the blood volume or RBC (Red Blood Cell), hence NO consumption in the blood. Parameters in the model are either obtained or fitted with experimental results from literature. Their model assumes a linear relationship of NO production with wall shear stress which in turn will be regulated by blood flow determined by branching characteristics of blood vessels. Moreover, the mathematical model includes transport of NO through the blood vessels in the tissue (in the defined volume of the model) as diffusion model,. The model was solved using Finite Elements method using the software COMSOL.

Their model results show that wall shear stress changes depending upon the distribution of RBC in the microcirculations of blood vessels, which leads to differential production of NO along the vascular network. Levels of NO at vascular walls can be less in branches which receive more blood flow, due to the balance between higher consumption of NO by RBC and production of NO due to high wall stress.  Their 3-D simulations showed the importance of capillaries such that NO can be concentrated in tissues far away in distance from arterioles facilitating much controlled NO regulation.

Though, the 3-D model developed by Chen et. al., (2011) is an idealized mathematical model of blood flow with production and consumption of NO, depending upon WSS, yet it shows importance of structure of blood vessels in distributions of NO in vessels and tissues. Such a model with proper extension to larger network can give more insights into differential distributions of NO as a function of blood flow and wall shear stress. As nano-medicine become sophisticated in years to come, information of distribution of NO in tissues and blood vessels can help the medicine to be more targeted.


Chen (2011) :

Mashour and Broock, Brain Res., 1999:

Mathematical Modes of NO Distribution in 2-D

Other research on Nitric Oxide and Vascular Biology on this Scientific Web Site include the following:

Nitric Oxide and Immune Responses: Part 1

Curator and Reporter: Aviral Vatsa, 10/18/2012

Clinical Trials Results for Endothelin System: Pathophysiological role in Chronic Heart Failure, Acute Coronary Syndromes and MI – Marker of Disease Severity or Genetic Determination?

Curator: Aviva Lev-Ari, 10/19/2012

Nitric Oxide and Sepsis, Hemodynamic Collapse, and the Search for Therapeutic Options

Curator and Reporter: Larry Bernstein, MD, 10/20/2012

Mitochondrial Damage and Repair under Oxidative Stress

Curator: Larry H Bernstein, MD, FCAP, 10/28/2012

Nitric Oxide and Immune Responses: Part 2

Curator: Aviral Vatsa, PhD, MBBS, 10/28/2012

Differential Distribution of Nitric Oxide – A 3-D Mathematical Model

Author: Anamika Sarkar, PhD, 10/28/2012

Statins’ Nonlipid Effects on Vascular Endothelium through eNOS Activation

Curator, EAW: Larry Bernstein, 10/8/2012

Nitric Oxide Nutritional remedies for hypertension and atherosclerosis. It’s 12 am: do you know where your electrons are?

Author and Reporter: Meg Baker, 10/7/2012.

Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography

Curator: Aviva Lev-Ari, 10/4/2012.

Coronary Artery Disease – Medical Devices Solutions: From First-In-Man Stent Implantation, via Medical Ethical Dilemmas to Drug Eluting Stents August 13, 2012

Author: Aviva Lev-Ari, PhD, RN, 8/13/2012

Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs

Curator; Aviva Lev-Ari, PhD, RN, 8/24/2012


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Reporter: Prabodh Kandala, PhD

Mice and monkeys don’t develop diseases in the same way that humans do. Nevertheless, after medical researchers have studied human cells in a Petri dish, they have little choice but to move on to study mice and primates.

University of Washington bioengineers have developed the first structure to grow small human blood vessels, creating a 3-D test bed that offers a better way to study disease, test drugs and perhaps someday grow human tissues for transplant.

The findings are published this week in the Proceedings of the National Academy of Sciences.

“In clinical research you just draw a blood sample,” said first author Ying Zheng, a UW research assistant professor of bioengineering. “But with this, we can really dissect what happens at the interface between the blood and the tissue. We can start to look at how these diseases start to progress and develop efficient therapies.”

Zheng first built the structure out of the body’s most abundant protein, collagen, while working as a postdoctoral researcher at Cornell University. She created tiny channels and injected this honeycomb with human endothelial cells, which line human blood vessels.

During a period of two weeks, the endothelial cells grew throughout the structure and formed tubes through the mold’s rectangular channels, just as they do in the human body.

When brain cells were injected into the surrounding gel, the cells released chemicals that prompted the engineered vessels to sprout new branches, extending the network. A similar system could supply blood to engineered tissue before transplant into the body.

After joining the UW last year, Zheng collaborated with the Puget Sound Blood Center to see how this research platform would work to transport real blood.

The engineered vessels could transport human blood smoothly, even around corners. And when treated with an inflammatory compound the vessels developed clots, similar to what real vessels do when they become inflamed.

The system also shows promise as a model for tumor progression. Cancer begins as a hard tumor but secretes chemicals that cause nearby vessels to bulge and then sprout. Eventually tumor cells use these blood vessels to penetrate the bloodstream and colonize new parts of the body.

When the researchers added to their system a signaling protein for vessel growth that’s overabundant in cancer and other diseases, new blood vessels sprouted from the originals. These new vessels were leaky, just as they are in human cancers.

“With this system we can dissect out each component or we can put them together to look at a complex problem. That’s a nice thing — we can isolate the biophysical, biochemical or cellular components. How do endothelial cells respond to blood flow or to different chemicals, how do the endothelial cells interact with their surroundings, and how do these interactions affect the vessels’ barrier function? We have a lot of degrees of freedom,” Zheng said.

The system could also be used to study malaria, which becomes fatal when diseased blood cells stick to the vessel walls and block small openings, cutting off blood supply to the brain, placenta or other vital organs.

“I think this is a tremendous system for studying how blood clots form on vessels walls, how the vessel responds to shear stress and other mechanical and chemical factors, and for studying the many diseases that affect small blood vessels,” said co-author Dr. José López, a professor of biochemistry and hematology at UW Medicine and chief scientific officer at the Puget Sound Blood Center.

Future work will use the system to further explore blood vessel interactions that involve inflammation and clotting. Zheng is also pursuing tissue engineering as a member of the UW’s Center for Cardiovascular Biology and the Institute for Stem Cell and Regenerative Medicine.


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