Profiling nitric oxide metabolites in patients with idiopathic pulmonary arterial hypertension

Intact nitric oxide (NO) signalling is critical to maintaining appropriate pulmonary vascular tone. NO bioavailability is reduced in patients with pulmonary arterial hypertension. This study aimed to examine the impact of NO plasma metabolites (NOx) relative to haemodynamic dysfunction and mortality in patients with idiopathic pulmonary arterial hypertension (IPAH).A total of 104 consecutive adult IPAH patients who had undergone genetic counselling when first diagnosed were enrolled in this prospective study.The median concentration of NOx (μmol·L^-1) was significantly lower in IPAH patients compared with healthy subjects, and was decreased further in 19 carriers of the bone morphogenetic protein-receptor type-2 (BMPR2) mutation compared to non-carriers. Reduced concentrations of NOx were correlated with mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR) and cardiac output. Compared with higher baseline NOx concentrations, patients with a NOx concentration of ≤10 μmol·L^-1 had a markedly worse survival. After adjustment for clinical features, a BMPR2 mutation and haemodynamics, a lower NOx level remained an increased risk of mortality.Patients with IPAH had lower levels of plasma NOx, which correlated inversely with mPAP, PVR and survival. Plasma NOx may be an important biomarker and prognostic indicator, suggesting that reduced NO synthesis contributes to the pathogenesis of IPAH.