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Background: Exercise capacity (EC) is a key prognostic indicator in adults with congenital heart disease (ACHD), closely associated with all-cause mortality. Thus, EC may serve a valuable tool for risk-stratification in ACHD. We propose a novel risk score incorporating EC, age, and lesion complexity to improve mortality risk prediction in ACHD.

Methods: This observational study utilized data from the Swedish National Register of Congenital Heart Disease. Adults aged 18 to 60 years who had completed at least one bicycle ergometer exercise test were included. EC was classified according to percentage of predicted capacity (% ECpred): normal (>70%), moderately impaired (50–70%), severely impaired (<50%). Patients were followed for ten years or until death. Odds ratios for mortality were used to derive a 5-point risk-score to estimate 10-year mortality, with the following point allocation: % ECpred 50–70 = 1 point, <50% = 2 points; age 25–40 years = 1 point, 40–60 years = 2 points; moderate/severe lesion complexity = 1 point. Internal validation of risk score resulted in a median AUC of 0.72 for training data, and 0.70 for test data.

Results: In total, 1,525 patients (mean age 31.1 ± 11.8 years; 44% women) were included, where 104 deaths occurred during follow-up. Risk scores ranged from 0 to 5, corresponding to 10-year mortality rates of 1%, 3%, 5%, 10%, 18%, and 34%, respectively.

Conclusion: A simple risk score incorporating exercise capacity, age, and congenital heart lesion complexity can effectively stratify ACHD patients to 10-year risk of all-cause mortality following an exercise test.