Comparative haemodynamic effects of transdermal vs intravenous nitroglycerin in acute myocardial infarction with elevated pulmonary artery wedge pressure.

The comparative haemodynamic effects of transdermal and intravenous nitroglycerin were evaluated in 16 patients with haemodynamic and radiographic left heart failure following a recent myocardial infarction. After the control period patients were randomized to transdermal (10 mg(24 h)-1) or intravenous (mean dose: 40 +/- 9 micrograms min-1) nitroglycerin. Haemodynamic parameters were recorded after 0.5,1,2,6,12,18 and 24 h during administration of the drug and 2 h after drug discontinuation. After the washout period the alternate system of nitroglycerin administration was adopted, according to a cross-over design. No differences were found in baseline measurements. Transdermal nitroglycerin reduced the pulmonary artery wedge pressure after 0.5 h (from 21 +/- 5 to 16 +/- 5 mmHg; P less than 0.05). The peak effect occurred at 2 h (12 +/- 5 mmHg). The improvement was sustained over 24 h. Transdermal nitroglycerin also significantly reduced mean pulmonary arterial and right atrial pressures (from 28 +/- 3 to 20 +/- 5 mmHg and from 6 +/- 3 to 2 +/- 2 mmHg at peak effect, respectively). Cardiac index increased from 2.5 +/- 0.6 to 2.8 +/- 0.8 l min-1 m-2 (P less than 0.05). There was no change in heart rate. Similar haemodynamic changes were observed after the intravenous infusion of nitroglycerin. Thus transdermal nitroglycerin is a safe and effective treatment of acute myocardial infarction with signs of left ventricular failure when an intravenous nitroglycerin infusion cannot be properly implemented.