Outcomes of patients with decreased arterial oxyhaemoglobin saturation on pulmonary arterial hypertension drugs

Abstract

Rationale: Drugs approved for the treatment of pulmonary arterial hypertension (PAH) improve long-term outcomes. These drugs have pulmonary vasodilator properties which may potentially cause a decrease in arterial oxyhaemoglobin saturation (SaO2) in some patients. Objectives: The present retrospective study of the French PAH Registry aimed to describe clinical characteristics and outcomes of patients showing a ≥ 3% decrease in SaO2 while treated with PAH drugs. Methods: We reviewed 719 PAH patients. The exclusion criteria were PAH associated with congenital heart disease and PAH with overt features of venous/capillaries involvement. Main Results: One hundred and seventy-three (24%) patients had a ≥ 3% decrease in SaO2. At diagnosis, they were older, with a lower diffusion capacity for carbon monoxide and a shorter 6-minute walk distance, when compared to those who did not display a ≥ 3% decrease in SaO2. The percentage of patients meeting the ESC/ERS low risk criteria at re-evaluation was significantly lower in those with a ≥ 3% decrease in SaO2 and more patients started long-term oxygen therapy in this group (16% versus 5%, p<0.001). A ≥ 3% decrease in SaO2 was associated with a poorer survival (Hazard Ratio 1.81:95% confidence interval 1.43-2.34; p<0.0001). In a multivariate Cox analysis, a ≥ 3% decrease in SaO2 was a prognostic factor independent of age at diagnosis and ESC/ERS risk stratification at follow-up. Conclusions: When treated with PAH drugs, a large subset of patients experience a ≥ 3% decrease in SaO2, which is associated with worst long-term outcomes and reduced survival.