Nitroglycerin and arterial compliance.

The primary effect of nitrates on the circulatory system is a relaxation of capacitance vessels on the venous and arterial side, while dilatation of resistance vessels (arterioles) is a secondary phenomenon, or occurs only at higher doses. Relaxation of arteries may augment flow in conditions where these vessels offer an increased resistance due to e.g. spasm. Relaxation of capacitance arteries explains in part the lower systolic blood pressure after nitroglycerin. Improved "Windkessel" function may augment diastolic arterial pressure and thus improve coronary perfusion. Some methods for measuring arterial compliance are described. It is suggested that more simple measurements of arterial pulsations may be used for studying nitroglycerin tolerance.