The response to inhaled nitric oxide in patients with pulmonary artery hypertension is not masked by baseline vasodilator use

Background Assessment of pulmonary vasodilator responsiveness is important in determining the prognosis and management of patients with pulmonary hypertension. Many patients, however, are already on vasodilators at the time of testing. It is unclear if these agents should be temporarily discontinued to improve the sensitivity of testing. Methods We examined the hemodynamic effects of nitric oxide (NO) inhalation in 60 patients with pulmonary arterial hypertension. Thirty-one of these patients were receiving medications with vasodilating properties. Vasodilator testing was performed with invasive measurement of pressure of the right side of the heart at baseline and during inhalation of 40 ppm NO. Results No significant demographic differences were seen between patients receiving and not receiving vasodilators. Similar reductions in mean pulmonary artery pressure (19 ± 12% vs 20 ± 12%, P = .734) and pulmonary vascular resistance (31 ± 18 vs 32 ± 16, P = .967) were seen in patients receiving and not receiving vasodilators. Using the definition of positive vasodilator response (≥20% drop in mean pulmonary artery pressure), 55% (17/31) of patients in the baseline vasodilator group had a positive response compared with 62% (18/29) of the patients not on vasodilators (P = .570). Conclusions Concurrent use of oral vasodilators does not appear to mask a significant response to inhaled NO on the pulmonary vasculature. Therefore, routine discontinuation of pulmonary vasodilators is likely unnecessary before vasodilator testing in patients with pulmonary arterial hypertension.