AJP - Heart and Circulatory Physiology, Vol 250, Issue 3 474-H481, Copyright © 1986 by American Physiological Society
Reactive hyperemia following one-beat coronary occlusions in the awake dog
R. J. Bache and D. S. Hess
This study was performed to examine the effect of alterations of cardiac
activity during brief coronary artery occlusions on the subsequent reactive
hyperemic response. Reactive hyperemia following coronary occlusions equal
in duration to one cardiac cycle were examined in 12 chronically
instrumented awake dogs while heart rate was maintained constant by cardiac
pacing. During continuous pacing, one-beat coronary occlusions resulted in
reactive hyperemia with excess flow equal to 220 +/- 23% blood flow debt
repayment. When coronary occlusions of identical duration were performed
while a single cycle of pacing was omitted during the interval of
occlusion, the subsequent reactive hyperemia was decreased. Conversely,
when coronary occlusion was produced during the first potentiated beat
following a single cycle of paired ventricular stimulation, the reactive
hyperemia was increased. Since, in the absence of coronary occlusion,
omitting a single paced beat caused a transient decrease in coronary flow,
while a single cycle of paired ventricular stimulation caused a brief
increase in coronary flow, the reactive hyperemic responses were corrected
for these perturbations in flow. Despite these corrections, the influence
of alterations of myocardial activity during the interval of occlusion
persisted, with the decreased reactive hyperemia when occlusion occurred
during an omitted beat and increased hyperemia when occlusion was performed
during a potentiated beat. These data indicate substantial coupling between
myocardial activity during coronary occlusions as brief as one cardiac
cycle in duration and the subsequent reactive hyperemic response.
