AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 25-H30, Copyright © 1987 by American Physiological Society
Metabolic mediation of single brief diastolic occlusion reactive hyperemic responses
N. Sadick, G. P. Dube, P. A. McHale and J. C. Greenfield Jr
We tested the hypothesis that coronary reactive hyperemia following a
single brief diastolic occlusion and subsequent systole is coupled to
myocardial metabolic activity and myocardial O2 consumption (MVO2). Sixteen
conscious dogs with Formalin-induced heart block were studied. A 400-ms
diastolic occlusion was introduced during normal ventricular pacing,
resulting in a reactive hyperemic repayment of 216 +/- 22%. A 400-ms
diastolic occlusion was also introduced during a higher level of myocardial
metabolic activity induced by ventricular paired pacing. MVO2 and mean
coronary blood flow were significantly increased relative to these
parameters during normal pacing, but reactive hyperemic repayment (189 +/-
18%) was not significantly changed. A third set of conditions was designed
to measure the response to a 400-ms occlusion during normal pacing while
eliminating the difference in magnitudes of myogenic influences that may
exist between paired pacing and normal pacing. Adenosine and phenylephrine
were infused intravenously during normal pacing to maintain mean aortic
pressure and mean coronary flow at paired pacing levels. MVO2 was similar
to O2 consumption during normal pacing in the absence of drug infusion, but
the reactive hyperemic repayment was significantly reduced (94 +/- 22%)
relative to paired pacing. Thus the magnitude of reactive hyperemic
response after a brief diastolic occlusion is related primarily to
myocardial metabolic activity.
