Pulmonary Function and response to treatment in pulmonary arterial hypertension (PAH)

PAH patients with impaired pulmonary function (PF) insufficient to be causal may have treatment outcomes that differ from those with normal PF. We investigate posthoc the impact of PF on treatment response in PAH patients from the AMBITION study, pooling data across treatment groups (Galie et al. NEJM 2015;373:834-44). 495 patients were grouped into normal PF (nPF) (FEV1 u0026 TLC≥80% pred) or abnormal PF (aPF) (FEV1 u0026/or TLC 50%, and TLCu003e60%, pred. Primary endpoint was the time to first clinical failure event. 50% of patients had aPF (27% Obstructive, 23% Restrictive), a greater proportion had a diagnosis of connective tissue disease (CTD) compared to nPF. Patients with nPF had a non-significant slightly lower rate of clinical failure than aPF patients (HR 0.767; 95%CI, 0.535-1.100) that was similar for obstructive and restrictive The adverse event profile was similar between groups. Mild PF impairment is frequent in PAH, especially PAH due to CTD, and is associated with a lower baseline 6MWD and a non-significant attenuated response to targeted therapy compared to patients with nPF (a higher proportion of whom had iPAH), despite comparable baseline haemodynamics.