Is pulmonary vascular resistance index predictive of exercise tolerance in adult patients with idiopathic pulmonary arterial hypertension ★

BackgroundClinical trials for adults with pulmonary arterial hypertension use exercise capacity, as measured by walking distance, as the primary endpoint to measure symptomatic improvement. In this article, we look at the relationship between walking distance and a hemodynamic variable, pulmonary vascular resistance index (PVRI), from the available trials.MethodsPatient-level data from 16 randomized controlled clinical trials were obtained. All idiopathic subjects with a baseline and study endpoint measurement of both hemodynamic and exercise endpoints were included. Changes from baseline in both endpoints and the relationship between the endpoints were summarized. Receiver operating characteristic curves were used to investigate the predictive ability. Measures of surrogacy were also calculated.ResultsThere is a weak correlation between changes in PVRI and exercise capacity. Receiver operating characteristic analysis shows a high false positive rate of using one variable to predict the other. Measures of surrogacy show the proportion of variability in exercise capacity explained by PVRI is approximately 5%.ConclusionsPVRI should not be used as a surrogate marker to predict changes in exercise capacity.