Inhaled nitric oxide testing in predicting prognosis in pulmonary hypertension due to left‐sided heart diseases

Abstract Aims The pathophysiology of pulmonary hypertension (PH) due to left‐sided heart disease (Group 2 PH) is distinct from that of other groups of PH, yet there are still no approved therapies that selectively target pulmonary circulation. The increase in pulmonary capillary pressure due to left‐sided heart disease is a trigger event for physical and biological alterations of the pulmonary circulation, including the nitric oxide (NO)–soluble guanylate cyclase–cyclic guanosine monophosphate axis. This study investigated inhaled NO vasoreactivity tests for patients with Group 2 PH and hypothesized that these changes may have a prognostic impact. Methods and results This was a single‐centre, retrospective study with a median follow‐up of 365 days. From January 2011 to December 2015, we studied 69 patients with Group 2 PH [age, 61.5 ± 13.0 (standard deviation) years; male:female, 49:20; left ventricular ejection fraction, 50.1 ± 20.4%; mean pulmonary arterial pressure, ≥25 mmHg; and pulmonary arterial wedge pressure (PAWP), >15 mmHg]. No adverse events were observed after NO inhalation. Thirty‐four patients with Group 2 PH showed increased PAWP (ΔPAWP: 3.26 ± 2.22 mmHg), while the remaining 35 patients did not (ΔPAWP: −2.11 ± 2.29 mmHg). Multivariate analysis revealed that increased PAWP was the only significant predictor of all‐cause death or hospitalization for heart failure (HF) after 1 year (hazard ratio 4.35; 95% confidence interval, 1.27–14.83; P = 0.019). The acute response of PAWP to NO differed between HF with preserved and reduced ejection fractions. Conclusions Patients with Group 2 PH were tolerant of the inhaled NO test. NO‐induced PAWP is a novel prognostic indicator.