AJP - Heart and Circulatory Physiology, Vol 245, Issue 1 82-H89, Copyright © 1983 by American Physiological Society
Effect of coronary occlusion on arrhythmias and conduction in the ovine heart
D. E. Euler, J. F. Spear and E. N. Moore
The proximal left circumflex coronary artery was occluded for 1 h in 16
open-chest sheep anesthetized with pentobarbital sodium. Epicardial
conduction was monitored at three or four sites within the ischemic zone
and one site in the normal zone. Eight of the sheep developed ventricular
fibrillation within the first 15 min of occlusion; the remaining sheep
survived the 1-h observation period. In the sheep that developed
spontaneous ventricular fibrillation, the circumflex perfused a
significantly greater amount of the left ventricle (44 +/- 3 vs. 39 +/- 3%;
P = 0.008). The occurrence of spontaneous ventricular fibrillation was
invariably preceded by a period of sustained (0.5-4 min) ventricular
tachycardia. Six of the surviving sheep developed episodes of sustained
(2-10 min) tachycardia that were self-terminating. The ischemic zone
electrograms showed continuous fractionated electrical activity during both
self-terminating tachycardias and tachycardias ending in fibrillation. The
continuous epicardial electrical activity did not appear to cause the
tachycardias but rather occurred as a result of the tachycardias. The
genesis of ventricular tachycardia and fibrillation in this model may
involve mechanisms different from ischemia-induced ventricular tachycardia
and fibrillation in canine and porcine hearts.
