Hemodynamic changes at the onset of spontaneous versus pacing-induced angina.

To determine the origin of angina pectoris at rest hemodynamic monitoring was performed for 24 to 72 hours in 25 patients with unstable angina who had pacing-induced angina during cardiac catheterization. During the monitoring period, seven patients had spontaneous epidsodes of angina at rest that could be compared with the pain-free periods and periods of pacing-induced angina. At the onset of spontaneous angina, the patients had a significantly lower mean double product (P is less than 0.005) and triple product (P is less than 0.025) than at the onset of pacing-induced angina. The mean double product (heart rate x systolic blood pressure) was 9,411 +/- 2,815 mm Hg/min during pain-free rest, 10,635 +/- 2,587 at the onset of spontaneous angina and 16,623 +/- 3,904 during pacing-induced angina. The mean resting pain-free triple product (heart rate x systolic blood pressure x ejection time) was 3,023 +/- 703 and 3,536 +/- 931 mm Hg/sec per min during, respectively, pain-free rest and spontaneous angina, and 4,350 +/- 938 mm Hg/sec per min during pacing-induced angina. These marked differences in the double and triple products were associated with a mean increase in pulmonary arterial diastolic pressure (from 10.7 mm Hg at rest to 14 mm Hg) at the onset of both spontaneous and pacing-induced angina. Although indirect, these data suggest that transient changes in coronary blood flow, rather than changes in myocardial work, may be primarily responsible for spontaneous angina at rest in certain patients with the syndrome of unstable angina.