Selective pulmonary vasodilation with inhaled aerosolized milrinone in heart transplant candidates

Abstract

Purpose: Selective pulmonary vasodilation is an advantageous method for testing the responsiveness of the pulmonary vasculature of heart transplant candidates. A pilot study was undertaken to test the hypothesis that inhaled aerosolized milrinone may cause selective pulmonary vasodilation. Methods: 18 consecutive male heart transplant candidates with either dilated or ischemic cardiomyopathy were included in this open clinical study. Nine of the patients had significant pulmonary hypertension with a mean pulmonary arterial pressure > 30 mmHg. After baseline measurements, 2 mg of milrinone was administered by ultrasonic nebulization. Pulmonary and systemic hemodynamics were measured ten, 30, and 60 min after inhalation. Results: After inhalation for ten minutes, milrinone induced a significant reduction of mean pulmonary arterial pressure (32.7 ± 9.1 vs 37.7 ± 7.5 mmHg, P = 0.01), pulmonary vascular resistance index (296 ± 150 vs 396 ± 151 dyn·sec-1·cm-1·m2, P = 0.02) and transpulmonary gradient (10.6 ± 5.5 vs 15 ± 4.9, P = 0.01) only in patients with significant pulmonary hypertension. There was no significant effect on mean arterial pressure or systemic vascular resistance at any time after inhalation in either group. Furthermore, there was no influence on extravascular lung water or intrathoracic blood volume. Conclusions: We conclude that inhaled aerosolized milrinone for a short period selectively dilates the pulmonary vasculature in heart transplant candidates with elevated pulmonary arterial pressure, without producing systemic side effects. Further comparative studies are necessary to evaluate possible advantages of milrinone compared to other inhaled vasodilators.