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Prolongation of Ventricular Refractoriness by Defibrillation Shocks May be Due to Additional Depolarization of the Action Potential
Author(s) -
DILLON STEPHEN M.,
MEHRA RAHUL
Publication year - 1992
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.1992.tb00988.x
Subject(s) - refractory period , medicine , prolongation , shock (circulatory) , depolarization , defibrillation , cardiology , carnivora , fissipedia , electrophysiology , anesthesia
Shock‐Induced Refractoriness Prolongation in Canines. Introduction: A comparison of the effects of shock timing and strength on the effective refractory periods (ERPs) of open chest canine hearts to the duration of depolarization in optically recorded action potentials from the rabbit heart was conducted in order to investigate the mechanism of ERP prolongation in the canine. Methods and Results: Studies were conducted in four open chest canines hearts and three isolated, perfused rabbit hearts. Shocks were applied during ventricular pacing and the strength and timing were varied. The shock voltage gradient was measured at the stimulating site used to assess the ERP in the canine and at the optical recording site in the rabbit. Shock voltage gradients ranged from 7.5 to 53 V/cm in the canine and 2 to 25 V/cm in the rabbit. Shock coupling intervals (CIs) were varied over a range of 15% to 105% of the control ERP (canine) and 10% to 115% of the control action potential duration (APD) (rabbit). Shocks prolonged the ERP in the canine and they caused an additional period of depolarization that prolonged the action potential in the rabbit. ERP and APD prolongation showed similar dependencies on the shock strength and CI: both increased with increasing shock strength and CI. Conclusion: ERP prolongation in the canine may be due to the same type of responses seen on the optically recorded action potentials in the rabbit. ERP prolongation by low‐strength shocks at long CIs in the canine may be due to graded responses and premature action potentials. ERP prolongation by high‐strength shocks over a range of CIs may be due to the additional depolarization time response that prolongs the action potential in rabbits. ( J Cardiovasc Electrophysiol, Vol. 3, pp. 442–456. October 1992 )