Abstract 15254: A Significant Difference Between Survival Estimates Predicted by National Institutes of Health and Pulmonary Hypertension Connection Models Based on Same Hemodynamic Measures in Patients with Pulmonary Arterial Hypertension Associated with Congenital Heart Disease

Abstract

Purpose: Pulmonary arterial hypertension (PAH) is a life-threatening condition and estimating survival of these patients is a challenge. The National Institutes of Health (NIH) equation and the more recent Pulmonary Hypertension Connection (PHC) registry formula use population means of pulmonary arterial pressure (PAP), right atrial pressure (RAP) and cardiac index (CI) to predict survival in PAH patients. However, the clinical relevance of these equations for estimating the survival of patients with PAH associated with congenital heart disease (APAH-CHD) remains to be determined.

Methods: Patients (>3 months of age) with APAH-CHD (mean pulmonary artery pressure [mPAP] >25 mmHg, pulmonary capillary wedge pressure ≤15 mmHg, pulmonary vascular resistance index >3 Wood units.m2) were included into the THALES (Turkish Congenital Heart DiseAse PuLmonary HypErtension Study) Registry. Survival estimates (SE) calculated from both NIH and PHC equations are compared by using the Wilcoxon test. The effect of age, pre-specified six-minute walk distance (6MWD) quartiles (qt1: >450 m; qt2: 374-450 m; qt3: 301- 374 m and qt4: <301 m) -found to be highly correlated to functional class- and PAH-targeted treatment status on SE were analysed using the Spearman test.

Results: The study population comprised 1034 APAH-CHD patients (male n=434, female n=600; mean age±standard deviation (SD) 16.91±17.91 years). The mean±SD 6MWD was 369±120 m. Mean±SD mPAP and RAP were 54.7± 22.2 and 8.95 ± 3.10 mmHg respectively and mean±SD CI was 3.86+4.18 L.min.m2. The PHC formula revealed higher 1, 2 and 3-year SE compared to the NIH equation for total group and each qt (44±22 and 74±17 for year 3 for NIH and PHC equations, respectively p<0.0001). While SE were comparable with respect to 6MWD qts and age within each model (p=NS), the PHC model found a significant correlation with PAH-targeted treatment status (r=0.243; p<0.001).

Conclusions: Our national registry of APAH-CHD patients showed a significant difference between SE predicted by NIH and PHC equations based on same hemodynamic measures. The PHC formula estimated significantly higher survival rates for PAH patients which appears to be a more appropriate comparator for the longitudinal survival analysis of our treated population.