Reflex Blood Pressure Control during Acute Myocardial Ischemia in the Conscious Dog

Abstract

Occlusions of the left circumflex coronary artery were performed before and after surgical denervation of sinoaortic baroreceptors in conscious, resting dogs. The removal of baroreceptors dramatically compromised arterial blood pressure maintenance. Mean pressure fell 9.1 mm Hg before denervation and 33.0 mm Hg after denervation. Aortic flow was reduced somewhat more without baroreceptors, and calculated total peripheral resistance fell 15% at the peak of occlusion in denervated dogs compared with a 2% increase in intact dogs. Flow studies indicated that femoral resistance was maintained or increased under the influence of active arterial baroreceptors but that femoral resistance fell dramatically in their absence. Renal resistance fell during coronary occlusion whether or not arterial baroreceptors were functional. Under both conditions, renal flow was maintained near its resting level. Results of this study suggest an important function in the maintenance of perfusion pressure by arterial baroreceptors during left circumflex coronary artery occlusion. The elimination of the arterial baroreceptors unmasked a dilatory response that reduced total peripheral resistance and, consequently, arterial blood pressure. Vessels which supply skeletal muscle and skin collectively were critically involved, but flow to the kidneys did not appear to play an important role.