The effect of low-dose intravenous nitroglycerin on pulmonary hypertension immediately after replacement of a stenotic mitral valve.

The postoperative effect of infusion of nitroglycerin on pulmonary vasomotor dynamics was studied in 28 patients undergoing valve replacement for mitral valve stenosis. A 30% reduction in mean pulmonary arterial pressure (38.74 +/- 8.3 to 26.92 +/- 7.72 mm Hg, p less than .001) and a 48.4% reduction in pulmonary vascular resistance index (12.08 +/- 4.19 to 5.61 +/- 1.61 U/m2, p less than .001) were observed after nitroglycerin. While pulmonary driving pressure (mean pulmonary arterial pressure minus left atrial pressure) dropped by 50.8%, cardiac and stroke volume indexes increased by 25.5% and 24.2%, respectively. The ratio pulmonary/systemic vascular resistance decreased from 34.14% to 20.9% (p less than .001). There were no significant changes in mean systemic arterial pressure (86.89 +/- 13.5 to 83.5 +/- 9.3 mm Hg, p = NS) or heart rate (97.43 +/- 20.45 to 99.36 +/- 20.9 beats/min, p = NS); left and right atrial pressures decreased by 19.5% and 9.5%, respectively. Systemic vascular resistance index decreased by 18.8%. We conclude that low-dose infusion of nitroglycerin reduces the pulmonary vascular resistance in patients with pulmonary hypertension, and consequently results in improvement in immediate postoperative hemodynamics after replacement of a stenotic mitral valve.