Aortic and radial pulse contour: different effects of nitroglycerin and prostacyclin.

Abstract

Through vasorelaxation, nitroglycerin is considered to reduce arterial wave reflection and to cause a more pronounced decrease in systolic pressure in the aorta (AoSAP) than in the radial artery (RaSAP). Our aim was to study how radial and aortic pulse wave configurations and the gradient (RaSAP-AoSAP) were affected by nitroglycerin and by prostacyclin, and how these changes correlated to stroke volume, vascular resistance/impedance, and wave reflection. Prostacyclin has not been studied in this context and was chosen because, in contrast to nitroglycerin, it does not reduce stroke volume and reduces afterload by arteriolar dilation. In 18 patients (53-81 yr old; heavily premedicated before coronary artery surgery), blood pressure was measured in both the radial artery and the ascending aorta (tipmanometry), and cardiac output was measured by thermodilution. Mean arterial pressure was reduced stepwise with each drug (mean total decrease 10-12 mm Hg). The initial RaSAP-AoSAP gradient (6 mm Hg) was increased 10 mm Hg by nitroglycerin and was not affected by prostacyclin. The nitroglycerin-induced increase in systolic gradient RaSAP-AoSAP correlated to decreases in stroke volume index, mean arterial pressure, and arterial elastance, but not to decrease in pulse wave augmentation. Thus, decreases in stroke volume index, not wave reflection, seem to be the main reason for an increased RaSAP-AoSAP when nitroglycerin is used in the elderly, hypertensive patient. We studied ascending aortic and radial pulse contours in patients scheduled for coronary artery surgery. The radial pulse wave can be used for interpretation of central hemodynamic changes during nitroglycerin-, but not prostacyclin-, induced hypotension.