Assessment of Survival in Patients With Primary Pulmonary Hypertension: Importance of Cardiopulmonary Exercise Testing

Abstract

Background — Primary pulmonary hypertension (PPH) is a life-threatening disease. Prognostic assessment is an important factor in determining medical treatment and lung transplantation. Whether cardiopulmonary exercise testing data predict survival has not been reported previously. Methods and Results — We studied 86 patients with PPH (58 female, age 46±2 years, median NYHA class III) between 1996 and 2001 who were followed up in a tertiary referral center. Right heart catheterization was performed and serum uric acid levels were measured in all patients. Seventy patients were able to undergo exercise testing. At the start of the study, the average pulmonary artery pressure was 60±2 mm Hg, average pulmonary vascular resistance was 1664±81 dyne · s · cm −5 , average serum uric acid level was 7.5±0.35 mg/dL, and average peak oxygen uptake during exercise (peak V̇ o 2 ) was 11.2±0.5 mL · kg −1 · min −1 . During follow-up (mean: 567±48 days), 28 patients died and 16 underwent lung transplantation (1-year cumulative event-free survival: 68%; 95% CI 58 to 78). The strongest predictors of impaired survival were low peak V̇ o 2 ( P <0.0001) and low systolic blood pressure at peak exercise (peak SBP; P <0.0001). In a multivariable analysis, serum uric acid levels (all P <0.005) and diastolic blood pressure at peak exercise independently predicted survival ( P <0.05). Patients with peak V̇ o 2 ≤10.4 mL · kg −1 · min −1 and peak SBP ≤120 mm Hg (ie, 2 risk factors) had poor survival rates at 12 months (23%), whereas patients with 1 or none of these risk factors had better survival rates (79% and 97%, respectively). Conclusions — Peak V̇ o 2 and peak SBP are independent and strong predictors of survival in PPH patients. Hemodynamic parameters, although also accurate predictors, provide no independent prognostic information.