Inhaled nitric oxide and hemodynamic evaluation of patients with pulmonary hypertension before transplantation

Objectives. We investigated the effect of inhaled nitric oxide and infused acetylcholine in patients with pulmonary hypertension undergoing cardiac catheterization before cardiopulmonary transplantation. Background. The fate of patients under consideration for transplantation of the heart or lungs, or both is influenced by the evaluation of their pulmonary vascular reactivity. Methods. We evaluated 11 patients who were classified into two groups on the basis of mean left atrial pressure >15 mm Hg (group I, n = 6) or ≤15 mm Hg (group II, n = 5). All patients inhaled nitric oxide at 80 ppm. This was preceded by an infusion of 10−6 mol/liter of acetylcholine in seven consecutive patients (n = 3 in group I, n = 4 in group II). Results. In group I, inhaled nitric oxide decreased pulmonary artery pressure from (mean ± SE) 71 ± 13 to 59 ± 10 mm Hg (p < 0.05), pulmonary vascular resistance from 14.9 ± 3.8 to 7.6 ± 1.7 Um2 (p < 0.05) and intrapulmonary shunt fraction from 17.8 ± 3.6% to 12.7 ± 2.1% (p < 0.05). Left atrial pressure tended to increase from 27 ± 4 to 32 ± 5 mm Hg (p = 0.07). In group II pulmonary vascular resistance decreased in response to nitric oxide from 36.4 ± 9.0 to 31.1 ± 7.9 Um2 (p < 0.05). Cardiac index, systemic pressure and resistance did not change in either group. Seven patients who received acetylcholine had no significant alteration in pulmonary hemodynamic variables. Conclusions. These preliminary observations suggest that nitric oxide is potent pulmonary vasodilator with minimal systemic effects. It may be useful in discriminating patients needing combined heart and lung transplantation from those requiring exchange of the heart alone.