Hemodynamic effects of diltiazem in hypertension.

Cardiac hemodynamics, diameter, blood flow velocity, and volumic flow of the brachial artery were studied before and after diltiazem administration in 11 patients with sustained essential hypertension. The study was compared with the hemodynamic effects of dihydralazine. The caliber of the brachial artery was evaluated with a pulsed Doppler velocimeter enabling the determination of the angle between the ultrasound beam and the vessel axis with a precision of 2%. After bolus administration of diltiazem, blood pressure and total peripheral resistance significantly decreased (P less than 0.001) while cardiac index and heart rate significantly increased (P less than 0.01). After 25 minutes of perfusion, cardiac output and heart rate returned toward control values, while blood pressure and total peripheral resistance remained decreased. The results contrasted with those observed after dihydralazine, which induced a sustained increase in cardiac index and heart rate. The caliber of the brachial artery decreased significantly (P less than 0.001) after dihydralazine and increased significantly after diltiazem (P less than 0.01). The study provided evidence that the antihypertensive effect of diltiazem was due to a fall in total peripheral resistance, associated with a transient baroreflex mediated tachycardia, and that--in addition to their effects on small arteries--vasodilating drugs may either increase (diltiazem) or decrease (dihydralazine) the caliber of peripheral large arteries.