Transdermal nitroglycerin reduces the frequency of anginal attacks but fails to prevent silent ischemia

The aim of this study was to objectively evaluate the effects of intermittent administration of transdermal nitroglycerin on effort tolerance, frequency of anginal attacks and presence of silent ischemic events that occur during normal daily activities.

Previous studies have shown that transdermal nitroglycerin patches reduce the incidence of anginal attacks and improve exercise capacity when given intermittently. However, no carefully controlled studies are available on the effects of these preparations (and their dosing schedule) on the occurrence of "silent" ischemic events during unrestricted daily activities.

Twelve men with chronic stable angina, a positive exercise test result and significant coronary artery disease completed a randomized, double-blind, placebo-controlled trial in which patches were worn either continuously or with overnight (8 h) removal. The effects of treatment were objectively assessed by both treadmill exercise testing and 24-h ambulatory electrocardiographic monitoring.

Only the intermittent dosing schedule afforded a small but significant improvement in exercise tolerance and prolonged exercise duration and time to ST segment depression. The frequency of anginal attacks was also reduced by both the continuous and intermittent treatment, but the effects on symptoms were not paralleled by a concomitant reduction in ischemic episodes recorded during ambulatory monitoring.

The results indicate that when used as monotherapy, intermittent transdermal nitroglycerin preparations lessen symptoms but are ineffective for the long-term prophylaxis of silent myocardial ischemia.