Improved Risk Prediction Using a Refined European Guidelines Instrument in Pulmonary Arterial Hypertension Related to Congenital Heart Disease

European guidelines advocate a goal-oriented treatment approach in pulmonary arterial hypertension (PAH), based on a comprehensive risk assessment instrument, which has been validated in several PAH subgroups. We investigated its discriminatory ability, and explored tricuspid annular plane systolic excursion (TAPSE) and revised thresholds to improve its predictability within the adult congenital heart disease (CHD) population.In total, 223 adults (42±16 years, 66% female, 68% Eisenmenger) were enrolled from five European PAH-CHD expert centers. Patients were classified as 'Low', 'Intermediate', or 'High' risk at baseline visit and at follow-up within 4-18 months. By the general PAH guidelines instrument, survival did not differ between the risk groups (P=n.s.), mostly due to skewed group distribution. Reclassifying patients using revised thresholds for N-terminal pro-brain natriuretic peptide (NT-proBNP) and 6-minute walk distance (6MWD) (i.e., 'Low', 'Intermediate', 'High' as <500, 500-1400, >1400 ng/l and >400, 165-400 and <165 m, respectively) and use of TAPSE ('Low', 'Intermediate', 'High' as >20, 16-20 and <16mm) significantly improved discrimination between the risk groups both at baseline and follow-up (P=0.001, ROC increase from 0.648 to 0.701), reclassifying 64 (29%) patients. Irrespective of follow-up risk group, survival was better for patients with higher proportions of low-risk variables. Improvement to a 'Low-risk' profile at a median of 9 months follow-up provided improved survival comparable to survival of patients who remained in the 'Low risk' group.In conclusion, the external validity of general risk instrument for PAH appeared to be of limited discriminatory value in PAH-CHD patients. We propose a refined risk instrument with improved discrimination for PAH-CHD.