Survival in pulmonary arterial hypertension: a reappraisal of the NIH risk stratification equation

TLDR

The study aimed to assess contemporary survival in pulmonary arterial hypertension and evaluate the accuracy of the NIH risk stratification equation. Using Kaplan–Meier analysis of 576 PAH patients (1991–2007), the authors compared observed survival to NIH predictions in 247 idiopathic/familial/anorexigen-associated cases and derived a new exponential regression equation based on mean pulmonary artery pressure, mean right atrial pressure, and cardiac index. Observed 1-, 3-, and 5-year survival rates (86%, 69%, 61%) were significantly higher than NIH predictions, indicating the NIH equation underestimates survival, while the new model aligns better with contemporary outcomes and may guide prognosis after validation.

Abstract

The aim of the present study was to determine contemporary survival in pulmonary arterial hypertension (PAH), and to investigate whether or not the National Institutes of Health (NIH) equation remains an accurate predictor of survival. In 576 patients with PAH referred during 1991–2007, observed survival was described using the Kaplan–Meier method. In patients with idiopathic, familial and anorexigen-associated PAH (n = 247), observed versus NIH equation predicted survival was compared. A new survival prediction equation was developed using exponential regression analysis. The observed 1-, 3- and 5-yr survival in the total cohort were 86, 69 and 61%, respectively. In patients with idiopathic, familial and anorexigen-associated PAH, the observed 1-, 3- and 5-yr survival (92, 75 and 66%, respectively) were significantly higher than the predicted survival (65, 43 and 32%, respectively). The new equation (P( t ) = e -A( x , y , z ) t , where P( t ) is probability of survival, t the time interval in years, A( x , y , z ) = e (−1.270–0.0148 x +0.0402 y –0.361 z ) , x the mean pulmonary artery pressure, y the mean right atrial pressure and z the cardiac index) performed well when applied to published contemporary studies of survival in PAH. Contemporary survival in the PAH cohort was better than that predicted by the NIH registry equation. The NIH equation underestimated survival in idiopathic, familial and anorexigen-associated PAH. Once prospectively validated, the new equation may be used to determine prognosis.