Coronary pressure-flow autoregulation protects myocardium from pressure-induced changes in oxygen consumption.
Pressure-flow autoregulation minimizes changes in coronary blood flow (CBF) when coronary perfusion pressure (CPP) is altered. This investigation determined if autoregulation also minimizes CPP-induced changes in coronary vascular volume (CVV) and CVV-dependent changes in myocardial oxygen consumption (MVO2). In 11 anesthetized dogs, the left anterior descending coronary artery was cannulated, and responses to 20-mmHg changes in CPP were examined over a range of CPP from 60 to 180 mmHg. Changes in CPP had no significant effect on systemic hemodynamics or on left ventricular end-diastolic segment length, end-systolic segment length, or percent segment shortening. In hearts with effective pressure-flow autoregulation [closed-loop gain (GC) > 0.4], CVV increased 0.06%/mmHg change in CPP. For the same hearts, MVO2 increased 0.04%/mmHg change in CPP. In hearts with ineffective autoregulation (GC < 0.4), CVV increased 0.97%/mmHg (P < 0.001 vs. autoregulating hearts), and MVO2 increased 0.41%/mmHg (P < 0.001 vs. autoregulating hearts). MVO2 and CVV were correlated (r = 0.69, P < 0.0001) independently of autoregulatory capability, but only when autoregulation was poor and capacitance was elevated did CPP significantly affect MVO2. We conclude that pressure-flow autoregulation protects myocardium from CPP-induced changes in CVV, which in turn produces changes in oxygen consumption.
Department of Physiology, University of North Texas Health Science Center at Fort Worth 76107-2699.
X J
XJ
Bai
T
T
Iwamoto
A G
AG
Williams
W L
WL
Fan
H F
HF
Downey
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001810:Blood Volume; D003326:Coronary Circulation / Q000502:physiology*; D004285:Dogs; D005260:Female; D006321:Heart / Q000502:physiology; D006439:Hemodynamics; D006706:Homeostasis; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption