The effect of intraaortic balloon counterpulsation on regional myocardial blood flow and oxygen consumption in the presence of coronary artery stenosis in patients with unstable angina.

To determine whether a reduction in myocardial oxygen demand or an increase in coronary blood flow or both are responsible for the salutory effect of intraaortic balloon counterpulsation (IABP) in relieving medically refractory angina, we assessed these variables in six patients in whom IABP was required for relief of myocardial ischemia. IABP decreased the rate-pressure product and aortic end-diastolic pressure, and the peak systolic aortic pressure and regional myocardial oxygen consumption declined in all but one patient. Peak and mean aortic diastolic pressures increased. Changes in regional coronary blood flow paralleled changes in peak systolic aortic pressure (r = 0.92, p less than 0.007). Thus, relief of angina during IABP could not be ascribed to an increase in regional coronary blood flow. Reduction of myocardial oxygen consumption is the most likely mechanism by which IABP relieves myocardial ischemia in patients with unstable angina pectoris.