Relationship of pulmonary arterial capacitance and mortality in idiopathic pulmonary arterial hypertension

OBJECTIVES The purpose of this study was to determine if pulmonary vascular capacitance predicts survival in patients with idiopathic pulmonary arterial hypertension (IPAH). BACKGROUND The prognosis of patients with IPAH is difficult to predict, despite knowledge of clinical and hemodynamic parameters previously identified as predictors. METHODS We proposed a capacitance index of stroke volume divided by pulmonary pulse pressure (SV/PP) and prospectively gathered data on IPAH Patients Who underwent a right heart catheterization. SV/PP was analyzed as a predictor of mortality after adjusting for other modifiers of risk. RESULTS During 4-year follow-up of 104 patients, 21 patients died. When compared with conventional markers, SV/PP was the strongest univariate predictor of mortality (hazard ratio 17.0 per ml(.)mm Hg-1 decrease, 95% confidence interval 13.0 to 22.0; p < 0.0001). In successive bivariate analysis, SV/PP was the only predictor of mortality. In quartile analysis, the lowest SV/PP quartile had a 4-year mortality of 61%; the highest SV/PP had no deaths. CONCLUSIONS The capacitance index (SV/PP) is a strong independent predictor of mortality in patients with IPAH.