Abstract 1634: A New Risk-Estimation Equation for Predicting Survival in Patients with Idiopathic, Familial, and Anorexigen-Associated Pulmonary Arterial Hypertension
Introduction: Estimated survival in idiopathic, familial, and anorexigen-associated pulmonary arterial hypertension (PAH) is currently based on an equation proposed by a 20-year-old NIH registry of primary pulmonary hypertension. Clinical trials in PAH have used the NIH equation in lieu of a placebo control group to suggest survival benefit. We hypothesized that the NIH equation is invalid in the current era, thereby necessitating a new survival equation.
Methods: We studied 259 patients with idiopathic, familial, and anorexigen-associated PAH referred to our center between1982–2007 (> 85% referred after 1995), all of whom underwent baseline hemodynamic testing. We collected vital statistics by Social Security Death Index, and used Weibull regression to develop a new survival equation.
Results: Mean age was 46 ± 14 years, 77% were female, 81% had functional class III-IV symptoms, mean treadmill exercise capacity was 3.8 ± 2.2 METs, and baseline hemodynamics were: RA pressure 9 ± 5 mmHg, mean PA pressure 52 ± 14 mmHg, CI 2.2 ± 1.0 L/min/m2, and pulmonary vascular resistance 14 ± 7 Wood units. Observed survival was significantly higher than survival predicted by the NIH equation. Our new equation (probability of survival = exp(−t^0.945 x exp(−1.354 −0.0136[mean PA pressure] − 0.0498[RA pressure]- 0.406[CI])))predicted survival well when applied to a recently published French registry of idiopathic PAH (predicted vs actual 1-year survival: 92% vs 89.3%, respectively).
Conclusions: The NIH equation for predicting survival in PAH is no longer valid. If prospectively validated, our new University of Chicago equation could become an important tool for risk estimation in PAH.