Orthotopic Heart Transplant (OHT): Effects of Autonomic Innervation / Denervation on Atrial Fibrillation (AF) Genesis and Maintenance

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Orthotopic Heart Transplant (OHT): Effects of Autonomic Innervation / Denervation on Atrial Fibrillation (AF) Genesis and Maintenance

June 30, 2013 by larryhbern

Orthotopic Heart Transplant (OHT): Effects of Autonomic Innervation / Denervation on Atrial Fibrillation (AF) Genesis and Maintenance

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

and

Curator: Aviva Lev-Ari, PhD, RN

Sympathetic stimulation increases heart rate (positive chronotropy), inotropy and conduction velocity (positive dromotropy), whereas parasympathetic stimulation of the heart has opposite effects.

Noheria A, Patel SM, Mirzoyev S, Madhavan M, Friedman PA, Packer DL, Daly RC, Kushwaha SS, Edwards BS, Asirvatham SJ.

Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California.
Pacing Clin Electrophysiol. 2013 Jun;36(6):741-7. http://dx.doi.org/10.1111/pace.12102. Epub 2013 Feb 25.

http://www.cvphysiology.com/Blood%20Pressure/ANS-medulla.gif

The medulla, located in the brainstem above the spinal cord, is the primary site in the brain for regulating sympathetic and parasympathetic (vagal) outflow to the heart and blood vessels. The nucleus tractus solitarius (NTS) of the medulla receives sensory input from different systemic and central receptors (e.g., baroreceptors and chemoreceptors).

The heart is innervated by vagal and sympathetic fibers. The right vagus nerve primarily innervates the SA node, whereas the left vagus innervates the AV node; however, there can be significant overlap in the anatomical distribution. Atrial muscle is also innervated by vagal efferents, whereas the ventricular myocardium is only sparsely innervated by vagal efferents. Sympathetic efferent nerves are present throughout the atria (especially in the SA node) and ventricles, including the conduction system of the heart.

Cardiac function is altered by neural activation. Sympathetic stimulation increases heart rate (positive chronotropy), inotropy and conduction velocity (positive dromotropy), whereas parasympathetic stimulation of the heart has opposite effects. Sympathetic and parasympathetic effects on heart function are mediated by beta-adrenoceptors and muscarinic receptors, respectively.

The overall effect of sympathetic activation is to increase cardiac output, systemic vascular resistance (both arteries and veins), and arterial blood pressure. Enhanced sympathetic activity is particularly important during exercise, emotional stress, and during hemorrhagic shock.

The actions of autonomic nerves are mediated by the release of neurotransmitters that bind to specific cardiac receptors and vascular receptors. These receptors are coupled to signal transduction pathways that evoke changes in cellular function.

Sympathetic Parasympathetic

Heart

Chronotropy (rate)

+ + + − − −

Inotropy (contractility)

+ + + − 1

Lusitropy (relaxation)

+ + + – 1

Dromotropy (conduction velocity)

+ + − − −

Vessels

Arterial constriction + + + 0

Venous constriction + + + 0

Relative magnitude of responses indicated by number of + or – signs.
1 More pronounced in atria than ventricles.

CV Physiology: Autonomic Innervation of the Heart and Vasculature
http://www.cvphysiology.com/Blood%20Pressure/BP008.htm

Ablation Therapy for Cardiac Arrhythmias

By Richard N. Fogoros, M.D., About.com Guide Updated November 18, 2011

The most common form of ablation is done during a specialized form of cardiac catheterization, performed by a type of doctor known as a cardiac electrophysiologist (heart rhythm specialist). These procedures are sometimes called “trans-catheter ablations.”

During trans-catheter ablation procedures, specialized electrode catheters are positioned inside the heart, and the cardiac electrical system is mapped, showing the abnormal electrical pathways that are often responsible for producing the rapid heart rate. If these abnormal pathways are identified, the tip of the catheter (a tube) is placed on the abnormal pathway and the pathway is ablated (eliminated). The ablation itself is accomplished by transmitting some form of energy through the catheter (heat energy, freezing energy, or microwave energy), in order to damage the tissue at the tip of the catheter.

Decreased postoperative atrial fibrillation following cardiac transplantation: the significance of autonomic denervation.

BACKGROUND: Endocardial ablation approaches have been proposed to targeting the retroatrial cardiac ganglia to treat atrial fibrillation (AF) . The potential value using this approach is unknown. Disruption of the autonomic inputs with orthotropic heart transplant (OHT) provides a unique opportunity to study the effects of autonomic innervation on AF genesis and maintenance.

The investigators hypothesized that due to denervation, the risk of postoperative AF would be lower following OHT compared to surgical maze even though both groups get isolation of the pulmonary veins.

METHODS: We reviewed 155 OHTs (mean age 52 ± 11 years, 72% males) and used 1:1 age-, sex-, and date-of-surgery-matched two control groups from patients undergoing surgical maze or only coronary artery bypass grafting (CABG). Using conditional logistic regression we compared the odds of AF within 2 weeks following OHT versus controls.

RESULTS: Postoperative AF occurred in 10/155 (6.5%) OHT patients.

The conditional odds of postoperative AF were lower for OHT as compared to controls (vs maze: odds ratio [OR] 0.27 [95% confidence interval (CI) 0.13-0.57], vs CABG: OR 0.38 [0.17-0.81], P = 0.003; and
on additional adjustment for left atrial enlargement, vs maze: OR 0.28 [0.13-0.60], vs CABG: OR 0.14 [0.04-0.47], P = 0.0009).

CONCLUSIONS:

Risk of postoperative AF is significantly lower with OHT as in comparison to surgical maze. As both surgeries entail isolation of the pulmonary veins but

only OHT causes disruption of autonomic innervation,

this observation supports a mechanistic role of autonomic nervous system in AF. The benefit of targeting the cardiac autonomic system to treat AF needs further investigation.

What Is Atrial Fibrillation? (afibrunner.wordpress.com)
Atrial fibrillation symptoms (findmedicalsolutions.com)
Promising Mid-Term Results From Thoracoscopic Ablation of Persistent Atrial Fibrillation Presented a (dailyfinance.com)
Atrial Fibrillation Genetic Risk (23andme.com)
Atrial Fibrillation: Preliminary Research Genetic Risk (23andme.com)
Intermountain Medical Center reseachers develop new 3-D technology to treat atrial fibrillation (eurekalert.org)
Excessive Supraventricular Ectopic Activity Is Indicative of Paroxysmal Atrial Fibrillation in Patients with Cerebral Ischemia (plosone.org)
Heart repair process found in zebrafish (utsandiego.com)
Paroxysmal Atrial Fibrillation Patients Should Undergo Depression Screening (medindia.net)
New risk assessment tool to predict stroke in patients with atrial fibrillation (medfinder.wordpress.com)

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

Imbalance of Autonomic Tone: The Promise of Intravascular Stimulation of Autonomics

Aviva Lev-Ari, PhD, RN

http://pharmaceuticalintelligence.com/2012/09/02/imbalance-of-autonomic-tone-the-promise-of-intravascular-stimulation-of-autonomics/

Renal Sympathetic Denervation: Updates on the State of Medicine

Aviva Lev-Ari, PhD, RN

http://pharmaceuticalintelligence.com/2012/12/31/renal-sympathetic-denervation-updates-on-the-state-of-medicine/

On Devices and On Algorithms: Prediction of Arrhythmia after Cardiac Surgery and ECG Prediction of an Onset of Paroxysmal Atrial Fibrillation

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Xarelto (Rivaroxaban): Anticoagulant Therapy gains FDA New Indications and Risk Reduction for: (DVT) and (PE), while in use for Atrial fibrillation increase in Gastrointestinal (GI) Bleeding Reported

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Sympathetic (red) and parasympathetic (blue) nervous system Русский: Аанатомия иннервации вегетативной нервной системы. Системы: симпатическая (красным) и парасимпатическая (синим) Українська: Аанатомія іннервації вегетативної нервової системи. Симпатична (червоним) та парасимпатична (синім) гілки Polski: Układ autonomiczny: czerwony – sympatyczny, niebieski – parasympatyczny. (Photo credit: Wikipedia)

Scheme of atrial fibrillation (top) and sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation. (Photo credit: Wikipedia)

English: A graphical representation of the Electrical conduction system of the heart showing the Sinoatrial node, Atrioventricular node, Bundle of His, Purkinje fibers, and Bachmann’s bundle (Photo credit: Wikipedia)

Posted in Biomedical Measurement Science, CABG, Cardiac & Vascular Repair Tools Subsegment, Ecosystems & Industrial Concentration in the Medical Device Sector, Electrophysiology, FDA Regulatory Affairs, Frontiers in Cardiology and Cardiovascular Disorders, Health Economics and Outcomes Research, International Global Work in Pharmaceutical, Medical Devices R&D Investment, Pharmaceutical Industry Competitive Intelligence, Pharmacotherapy of Cardiovascular Disease | Tagged Atrial fibrillation, Cardiology, Cardiovascular Disorders, Cedars-Sinai Medical Center, Heart disease, Los Angeles | 3 Comments

3 Responses

on June 30, 2013 at 10:02 AM | Reply Heart transplantation research in the next decade–a goal to achieving evidence-based outcomes | Pharmaceutical Intelligence

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on June 30, 2013 at 11:39 AM | Reply Vasoplegia in orthotopic heart transplants | Pharmaceutical Intelligence

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on July 16, 2013 at 3:46 PM | Reply Heart Transplant (HT) Indication for Heart Failure (HF): Procedure Outcomes and Research on HF, HT @ Two Nation’s Leading HF & HT Centers | Pharmaceutical Intelligence

I actually consider this amazing blog , âSAME SCIENTIFIC IMPACT: Scientific Publishing –
Open Journals vs. Subscription-based « Pharmaceutical Intelligenceâ, very compelling plus the blog post ended up being a good read.
Many thanks,Annette

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