Nocturnal hypoxemia, but not sleep apnea, is associated with a poor prognosis in patients with pulmonary arterial hypertension

Abstract

Background: Sleep apnea (SA) can cause repeated nocturnal arterial oxygen desaturation and result in acute increase in pulmonary arterial pressure (PAP). The presence of SA is associated with a poor prognosis in patients with chronic left-sided heart failure, but little is known for patients with pulmonary arterial hypertension (PAH). Methods and Results: We enrolled 151 patients with PAH (44±16 years old, male/female=37/114). They were all in the Nice Classification group 1 (idiopathic PAH/associated PAH=52/48%, mean PAP of 46±16 mmHg). They underwent right-heart catheterization and a sleep study with simplified polysomnography. Averaged percutaneous oxygen saturation (SpO2) during sleep was measured and an apnea-hypopnea index >5 was defined as SA. SA was noted in 58 patients (obstructive SA/central SA: 29/29). Over an average follow-up of 1,170±763 days, 32 patients died. By Kaplan-Meier analysis, there was no significant difference in deaths of patients with and without SA (χ2=2.82, P=0.093). On the other hand, the mortality in patients with lower averaged SpO2 was significantly higher than in those with higher averaged SpO2 (χ2=14.7, P<0.001) and that was the only independent variable related to death in multivariate Cox proportional hazards analysis. Conclusions: SA in patients with PAH was not associated with worse prognosis, unlike left ventricular heart failure, but nocturnal hypoxemia was related to poor prognosis.