AJP - Heart and Circulatory Physiology, Vol 241, Issue 4 654-H661, Copyright © 1981 by American Physiological Society
Limitations of postextrasystolic potentiation in identifying ischemic myocardium
A. L. Cornish, H. G. Hanley, W. O'Connor, J. D. Slack, T. A. Patrick and J. S. Cole
To evaluate the usefulness of postextrasystolic potentiation in
differentiating ischemic yet viable myocardium from infarcted myocardium,
20 dogs were chronically instrumented with left ventricular pressure
gauges, left circumflex coronary artery flow probes, occluders, pacing
wires, and ultrasonic segment-length transducers. Ten dogs had acute (1 h)
coronary occlusions followed by reperfusion (4 days) and were then killed.
Ten more dogs had more prolonged (1 mo) occlusions and were then killed.
Timed premature ventricular contractions were induced, and the
postextrasystolic beat was evaluated. In ischemic segments that were
hypokinetic, postextrasystolic potentiation of shortening occurred in both
groups. In ischemic segments that were akinetic or dyskinetic, potentiation
of shortening did not occur in either group. Both groups showed recovery of
shortening, and histologically normal myocardium was identified in the
region between the segments in all animals. Thus, akinetic and dyskinetic
segments did not show postextrasystolic potentiation of shortening, even
though the tissue was viable and showed functional recovery. Failure to
improve shortening after a premature ventricular beta in an ischemic
segment does not necessarily indicate nonviable myocardium.
