Does arterial oxygenation during exercise add prognostic value in pulmonary arterial hypertension?

Background: The 6-min walking distance (6MWD) is often used to assess prognosis in pulmonary arterial hypertension (PAH) patients. Whether or not changes in arterial oxygen saturation (SpO(2)) during exercise add prognostic value to the 6MWD in these patients is unclear. The objective of this study was to investigate if SpO(2) changes during exercise adds prognostic value to the 6MWD in PAH patients. Methods: Ambispective study that includes 137 patients with PAH: 38 idiopathic/heritable (i/h PAH), 42 with connective tissue disease (CTD-PAH), 34 with porto-pulmonary hypertension (PoPH), 21 with HIV-associated PAH and 2 with pulmonary venous occlusive disease (PVOD). Patients were characterized and, treated according to international recommendations, and were followed-up for 5 years. To integrate SpO(2) changes during exercise, we calculated the desaturation distance ratio (DDR) either in its original form (from a maximal theoretical value of 100%) or the actual resting SpO(2) value of the patient (new DDR) as well as the distance saturation product (DSP). Results: (1) during follow-up, 40 patients died (29.2%); (2) results confirmed the prognostic value of the 6MWD (AUC 0.913 [IQR 0.868-0.958]; p < 0.0001), original DDR (AUC 0.923 [0.881-0.966]; p < 0.001), New DDR (AUC 0.917 [0.872-0.961], p < 0.001), and DSP (AUC 0.914 [0.869-0.959], p < 0.001); and, (3) neither the original or new DDR or DSP added significant prognostic value to 6MWD in these patients. Conclusions: Consideration of three different composite indices of arterial oxygenation changes during exercise does not add prognostic value to that of the 6MWD in patients with PAH.