Exercise to predict outcome in idiopathic vs associated pulmonary arterial hypertension

Abstract

We tested the ability of exercise testing to predict not only survival but also time to clinical worsening in idiopathic versus associated pulmonary arterial hypertension (PAH).

Hundred thirty-six patients with PAH (85 idiopathic and 51 with associated conditions), underwent cardiopulmonary exercise testing and a 6-minute walk test. Death or transplantation, and clinical worsening events were recorded.

Thirty-two patients died and 4 had lung transplantation. At univariate analysis, PAH patients survival was associated with oxygen uptake (VO2) at peak exercise and at anaerobic threshold, ventilatory equivalent for CO2 (VEVCO2) at anaerobic threshold (at), VE/VCO2slope and distance walked. Time to clinical worsening was associated with peakVO2 and VO2at, VEVCO2at, end-tidal CO2 partial pressure measured at anaerobic threshold, peakO2 pulse, increase in O2pulse and distance walked. At multivariable analysis, distance walked and VEVCO2at predicted survival, and only peakVO2 predicted time to clinical worsening. The ROC curve-derived cut-off values were 305 m for the 6-min walk distance, 54 for VEVCO2at and 11.6 mL·Kg⁻¹.min for peakVO2. In the subgroup of associated PAH, no variable independently predicted survival or clinical worsening.

We conclude several exercise variables predict survival and clinical stability in idiopathic PAH. Exercise variables are less accurate predictors of outcome in associated PAH.