Benefit of nitroglycerin on arterial stiffness is directly due to effects on peripheral arteries

Alfredo L Pauca ¹, Neal D Kon ¹ and Michael F O'Rourke ^2*

¹ Wake Forest University School of Medicine, United States
² UNSW/St. Vincent's Clinic, Australia

^* To whom correspondence should be addressed. E-mail: m.orourke{at}unsw.edu.au.

Accepted 2 February 2005

Abstract

Objective: To determine in what way the vasodilator nitroglycerin (NTG) alters arterial stiffness and improves left ventricular (LV) afterload.

Background: Controversy exists regarding the effects of vasodilator drugs on stiffness of proximal (predominantly elastic) and peripheral (predominantly muscular) arteries, with recent noninvasive studies favouring the former, and downplaying effects of wave reflection from peripheral arteries.

Methods: Ascending aortic pressure waves were measured with fluid-filled catheters of high fidelity in 50 patients undergoing cardiac surgery, prior to cardiopulmonary bypass, both before and after IVI infusion of NTG. In all 50 patients, wave reflection was identifiable as a secondary boost to late systolic pressure, permitting the pressure wave to be separated into a primary component, attributable to LV ejection and properties of the proximal aorta, and a secondary component attributable to reflection of the primary wave from the peripheral vasculature.

Results: NTG infusion caused no change in amplitude of the primary wave (0.0, SD 1.4mmHg, NS), but substantial reduction (14.6, SD9.8mmHg, P<0.0001) in amplitude of the secondary reflected wave. Fall in mean pressure was attributable to a mix of arteriolar and venous dilation, with relative contributions unable to be separated.

Conclusion: Favourable effects of NTG on arterial stiffness can be attributed to effects on peripheral muscular arteries, causing reduction in wave reflection. Results conform with previous invasive studies on vasodilator agents, and their known effects on calibre and compliance of muscular arteries.

Keywords: arterial stiffness, nitroglycerin, wave reflection

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