AJP - Heart and Circulatory Physiology, Vol 233, Issue 3 392-H348, Copyright © 1977 by American Physiological Society
Loss of regional ventricular postextrasystolic potentiation after coronary occlusion in dogs
B. Crozatier, D. Franklin, P. Theroux, H. Tomoike, S. Sasayama and J. Ross Jr
Postextrasystolic potentiation following coronary artery occlusion was
studied serially using pairs of ultrasonic crystals to measure regional
myocardial function in control, marginally ischemic, and ischemic segments
of the left ventricle in dogs. Prior to coronary occlusion (CO), percent
shortening in control (normal) segments increased by an average of 51.4 +/-
4.6% in the beat after a premature ventricular contraction (post-PVC beat),
and this response changed little after coronary occlusion. During the 1st
min after CO, in ischemic segments, systolic expansion developed but was
replaced by active shortening in post-PVC beats; however, after 3 min of CO
(average) and thereafter, there was no net positive shortening in post-PVC
beats. In marginally ischemic segments early after CO, hypokinesia
developed, but there was marked augmentation of percent shortening (208.6
+/- 32.6%) which persisted in post-PVC beats even after 2 h. It is
concluded that loss of postextrasystolic potentiation occurs rapidly in
ischemic regions after CO and is not indicative of irreversible damage;
partially ischemic regions retain this mechanism for prolonged periods.
