Thirty patients (24F, 6M, aged 40.5 +/- 15.4 years) with chronic precapillary pulmonary hypertension (primary pulmonary hypertension--PPH)--20 pts, associated with connective tissue disease--6 pts, due to thromboembolism--2 pts and Eisenmenger syndrome--2 pts) were submitted to 5 min inhalation of 10 and 20 ppm of nitric oxide (NO) during right heart catheterization. For the whole group this test resulted in minimal changes in directly assessed hemodynamics. However, individual reactions differed markedly between patients. Assuming three levels of criteria of preserved reactivity (liberal, standard, demanding) 11/30 (37%) patients had fall in PAP and PVR > or = 20% from baseline, 4/30 (13%) decreased PAP and PVR by > or = 20% and 30% respectively and 2 (7%) patients normalized PAP and decreased PVR > or = 50% from baseline, respectively. Interestingly, even liberal criteria were fulfilled positive test was observed exclusively in patients with primary PH. In one patient with connective tissue disease and systemic hypertension acute pulmonary congestion appeared during NO testing, with concomitant increase in systemic arterial pressure and pulmonary wedge pressure. No other complications were noted and no rebound PH after discontinuation of NO was observed in any of the patients.
Conclusion: 1. Acute inhaled nitric oxide test appears to be safe in patients with PH and no coexisting left heart dysfunction. 2. It allows for stratification of patients according to the degree of preserved pulmonary vascular reactivity. However, criteria which would permit to select optimal treatment based on the results of NO test require further studies.