Influence of sublingual nitroglycerin on the digital circulation of man.

By means of the digital rheoplethysmographic (RPG) method, the effect of sublingually administered nitroglycerin (NTG), 1/200 gr (0.3 mg), on the digital circulation was studied in 17 normal subjects and 5 patients with ischemic heart disease and angina pectoris. NTG produced dilatation of all digital vessels, reflected especially by increases in total digital volume. NTG produced marked changes in the dicrotic notch of the pulse wave, noted also in inflow volume curves but not in outflow volume curves. The dicrotic notch was displaced later on the descending limb of the digital pulse wave and became deeper and more prominent after NTG. It is suggested that NTG produces disproportionate dilatation of the arterial system, having its greatest effect on arteries near the heart, including the coronaries and great vessels branching off the aorta, and on left intraventricular cavity pressure. This greater regional vasodilatation of vessels near the heart could delay closure of the aortic valve, producing a delayed and prominent dicrotic notch of the pulse wave.