Circulation, Vol 74, 401-409, Copyright © 1986 by American Heart Association
S Kimura, AL Bassett, T Kohya, PL Kozlovskis and RJ Myerburg
We studied the effects of ischemia on transmembrane action potentials,
conduction time, and refractory periods of both endocardial and epicardial
muscle cells of coronary-perfused cat left ventricles. Oxygenated Tyrode's
solution was perfused through the left anterior descending coronary artery,
while the preparation was superfused with Tyrode's solution gassed with 95%
N2 and 5% CO2. Transmembrane action potentials recorded simultaneously from
endocardial and epicardial cells were normal during coronary perfusion.
When perfusion was discontinued ("ischemia"), rapid deterioration of action
potentials and prolongation of conduction time were observed in both
endocardial and epicardial cells. The magnitude of the reduction of action
potential amplitude and action potential duration (APD), and of
prolongation of conduction time, was greater in epicardial cells than in
endocardial cells, although the change in resting membrane potential was
almost the same. However, APD of endocardial cells decreased progressively
during 30 min of ischemia, whereas APD of epicardial cells was reduced
maximally at 10 min and then partially recovered. Shortening of refractory
periods of endocardial cells paralleled APD shortening, whereas refractory
periods of epicardial cells decreased for the first 10 min and then
increased. At 10 min of ischemia, APD and refractory periods of epicardial
cells were significantly shorter than those of endocardial cells. At 30 min
of ischemia, refractory periods of epicardial cells exceeded those of
endocardial cells because of development of greater postrepolarization
refractoriness in epicardial cells. Accompanying these different changes in
APD and refractory periods of endocardial and epicardial cells, spontaneous
extrasystolic impulses increased and rapid runs of extrasystolic impulses
could be induced by extrastimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
ARTICLES
Simultaneous recording of action potentials from endocardium and epicardium during ischemia in the isolated cat ventricle: relation of temporal electrophysiologic heterogeneities to arrhythmias
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