A possible explanation for the absence of anti-anginal properties of transdermal nitroglycerin units: an echocardiographic study.

The failure of clinical trials to demonstrate any anti-anginal properties of the transdermal nitroglycerin units has resulted in the re-evaluation of one such product, Transiderm-Nitro. Haemodynamic assessment following the application of 10, 20 and 40 cm2 units has been made in eight healthy volunteers over a 6 h period. Measurements of heart rate, blood pressure, stroke volume and left ventricular dimension (by 'M' mode echocardiography) were made 2 h after the application of the units. End diastolic dimension fell by 5.2% and stress by 12.6% implying a reduction in myocardial oxygen consumption. However this was offset by an increase in double product of 10.7% and in circumferential fibre shortening of 23.4%. These results imply that the doses used produce venodilatation leading to a reduction in myocardial oxygen consumption. However this is counterbalanced by the reflex induced increase in heart rate and inotropic state. It suggests therefore that much larger doses are required to produce significant anti-anginal effects.