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Posts Tagged ‘Los Angeles’


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
ANS- autonomic innervation of heart

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.
  1. 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
  2. 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.

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

https://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

https://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

Justin D Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/05/07/on-devices-and-on-algorithms-arrhythmia-after-cardiac-surgery-prediction-and-ecg-prediction-of-paroxysmal-atrial-fibrillation-onset/

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

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2012/11/04/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/
Sustained Cardiac Atrial Fibrillation: Management Strategies by Director of the Arrhythmia Service and Electrophysiology Lab at The Johns Hopkins Hospital

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2012/10/16/sustained-cardiac-atrial-fibrillation-management-strategies-by-director-of-the-arrhythmia-service-and-electrophysiology-lab-at-the-johns-hopkins-hospital/
Stroke and Bleeding in Atrial Fibrillation with Chronic Kidney Disease

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2012/08/16/stroke-and-bleeding-in-atrial-fibrillation-with-chronic-kidney-disease/
Atrial Fibrillation: The Latest Management Strategies

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2012/07/16/atrial-fibrillation-the-latest-management-strategies/
Genetics of Conduction Disease: Atrioventricular (AV) Conduction Disease (block): Gene Mutations – Transcription, Excitability, and Energy Homeostasis

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/04/28/genetics-of-conduction-disease-atrioventricular-av-conduction-disease-block-gene-mutations-transcription-excitability-and-energy-homeostasis/

Minimally Invasive Structural CVD Repairs: FDA grants 510(k) Clearance to Philips’ EchoNavigator – X-ray and 3-D Ultrasound Image Fused

Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/03/21/minimally-invasive-structural-cvd-repairs-fda-grants-510k-to-philips-echonavigator-x-ray-and-3-d-ultrasound-image-fused/

Accurate Identification and Treatment of Emergent Cardiac Events

Larry Bernstein, MD, FCAP
https://pharmaceuticalintelligence.com/2013/03/15/accurate-identification-and-treatment-of-emergent-cardiac-events/

Percutaneous Endocardial Ablation of Scar-Related Ventricular Tachycardia

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2012/07/18/percutaneous-endocardial-ablation-of-scar-related-ventricular-tachycardia/

Sympathetic (red) and parasympathetic (blue) n...

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 ...

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 Ele...

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)

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