Background: Severe preoperative pulmonary hypertension predicts a poor outcome after heart transplantation and therefore pulmonary vasoreactivity is frequently evaluated in the pretransplantation screening. Among the i.v. organic nitrates used in this evaluation, isosorbide dinitrate and nitroglycerin differ in their pharmacokinetics, and isosorbide dinitrate has been suggested to be more selective in its effects on pulmonary vasculature than nitroglycerin.
Methods: Haemodynamic effects of nitroglycerin and isosorbide dinitrate were compared in 8 patients with end-stage cardiomyopathy. Each patient was given increasing i.v. infusion-doses of the two nitrates in a random order and double-blind and cross-over fashion until the target of at least 25% decrease in mean pulmonary artery pressure was achieved.
Results: A total dose of 11 (3-20) (mean, 95% confidence interval) microgram kg-1 of nitroglycerin and that of 87 (12-161) micrograms kg-1 of isosorbide dinitrate were given during the infusions of 20 (14-27) and 28 (18-37) min duration, respectively. With these doses producing similar acute decreases in mean pulmonary artery pressure, both nitroglycerin and isosorbide dinitrate also showed equal effects on pulmonary and systemic vascular resistances as well as on other systemic and right ventricular haemodynamic parameters.
Conclusion: We conclude that there is no difference between i.v. nitroglycerin and isosorbide dinitrate in their selectivity on the pulmonary vasculature in patients with end-stage cardiomyopathy.