Haemodynamic effects of angina pectoris, and of nitroglycerin in normal and anginal subjects.

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Abstract
Observations were made of total body O2 consumption, heart rate, cardiac output, stroke volume, and blood pressure in 10 normal subjects and in 22 patients with angina pectoris, at rest and during exercise in the sitting posture, before and then after the administration of nitroglycerin. In the absence of nitro-glycerin, resting values and hemodynamic response to exercise were comparable in normal subjects and patients with angina pectoris, in spite of the presence of anginal pain in all the patients during exercise observations. Changes observed 3 min. after nitroglycerin taken at rest were again comparable in normal subjects and patients. While cardiac output, diastolic pressure, and pressure time - min. were unchanged, there was a small increase in heart rate and a fall in stroke volume and systolic pressure. In 5 normal subjects performing steady exercise for 12 min. nitroglycerin caused a fall in systolic pressure which was significant from 3 min. to 9 min. Diastolic pressure was unchanged. Cardiac output appeared first to fall, but by 9 min. had exceeded control values. These changes were small and not statistically significant. When exercise performance was studied before and 8-10 min. after nitroglycerin in 10 normal subjects and in 17 patients with angina pectoris, there was a significant increase in cardiac output and stroke volume. There was a small reduction in systolic mean pressure and pressure time - mn., which was significant only in the normal subjects. Heart rate and diastolic pressure were unchanged. These changes, together with a reduction of ventricular dimensions, would tend to reduce energy expenditure of ventricular muscle. They are, however, small and the therapeutic action of this drug in angina pectoris may well result also from its direct effect on coronary arteries.