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β-Adrenergic stimulation and rapid pacing mutually promote heterogeneous electrical failure and ventricular

Vivek Garg1, Tyson Taylor2, Mark Warren2

  • 1Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah;

American Journal of Physiology. Heart and Circulatory Physiology
|February 26, 2015
PubMed

Insights

Rapid heart rhythms and beta-adrenergic stimulation accelerate electrical failure during global ischemia. These factors contribute to sudden cardiac arrest outcomes like asystole and ventricular fibrillation.

Area of Science:

  • Cardiovascular Physiology
  • Cardiac Electrophysiology
  • Sudden Cardiac Arrest Research

Background:

  • Sudden cardiac arrest (SCA) is a critical condition often involving global ischemia, catecholamine surge, and rapid heart rhythms (RHR).
  • Global electrical failure, leading to asystole, is a prevalent and severe outcome of SCA.
  • The specific roles of catecholamines and RHR in electrical failure during SCA require further elucidation.

Purpose of the Study:

  • To investigate the hypothesis that beta-adrenergic stimulation (βAS) and RHR accelerate electrical failure in globally ischemic hearts.
  • To understand the mechanisms underlying electrical depression and the development of ventricular fibrillation (VF) during ischemia.

Main Methods:

  • Optical mapping of action potential (OAP) in isolated rabbit ventricles subjected to 30-minute global ischemia.
  • Experimental groups included varying pacing rates (300 ms vs. 200 ms cycle length) and the presence or absence of isoproterenol (a β-agonist).
  • Motion artifacts were minimized using 2,3-butanedione monoxime.

Main Results:

  • RHR and βAS synergistically accelerated the decline in OAP upstroke velocity and the expansion of inexcitable regions.
  • Ventricular inexcitability developed more rapidly in the left ventricle (LV) than the right ventricle (RV).
  • Both RHR and βAS shortened the time to ventricular fibrillation (TVF); the time to 10% LV inexcitability strongly correlated with TVF.

Conclusions:

  • Beta-adrenergic stimulation and rapid heart rhythms are significant contributors to electrical depression and failure in the globally ischemic heart.
  • These factors may play a crucial role in the adverse outcomes of SCA, including asystole and persistent VF.
  • Targeting catecholamine surges and managing heart rate could be important strategies in managing SCA.

Keywords:
inexcitabilitymyocardial ischemiaoptical mappingventricular fibrillationβ-adrenergic stimulation

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