Cyclic fluctuations in coronary blood pressure and flow induced by coronary artery constriction.

Slow cyclic fluctuations were frequently observed in blood pressure of the distal portion of the partially constricted coronary artery of anesthetized dogs. Lowering the mean peripheral coronary blood pressure below 50% of the control value was required for initiation of fluctuations. Each fluctuation in pressure was composed of 2 phases; the phase of rise and phase of fall. Almost invariably, the phase of rise and phase of fall were accompanied by increase and decrease in coronary blood flow, respectively. When the mean peripheral coronary blood pressure fell below 20% of the control value during the phase of fall, systolic bulge and elevation of the ST segment of surface ventriculra electrocardiogram occurred. Period duration of each fluctuation ranged from 30 sec to 14 min. The cyclic fluctuations in pressure, flow, electrocardiogram and left ventricular wall motion were eliminated by nitroglycerin, but were not affected by phentolamine, propranolol, atropine, cervical vagotomy, and stellectomy.