Mortality rates in adults with severe congenital heart disease: insights from the National Congenital Heart Disease Registry of Australia.

Background: Survival into adulthood with congenital heart disease (CHD) has improved, but premature mortality remains common. Long-term, multi-centre data are scarce. We used a validated complexity algorithm to select "severe CHD" patients from the National CHD Registry of Australia, quantifying mortality by ventricular physiology, residential remoteness and treating-centre location. Methods: From 70185 CHD patient records, we identified 6557 patients classified as "severe" by 2020 European Society of Cardiology guidelines, born from 1980 onwards and alive at 16 years old. We found 2118 single-ventricle patients, 3674 two-ventricle and 765 with insufficient information for classification. Residence was grouped into Major Cities, Inner Regional, and Outer Regional/Remote. Vital status follow-up was to December 31, 2023. Kaplan-Meier curves were used to compare survival. Results: Overall, 25-year survival was 96.9 % and 40-year survival was 89.0 %. Survival differed by physiology: single-ventricle survival was 96.4 % at 25 years and 88.2 % at 40 years, while two-ventricle survival was better, at 97.6 % at 25 years and 90.8 % at 40 years (p = 0.0015). Patients managed in Sydney/Melbourne fared better than those treated elsewhere, particularly after age 35 (25-year survival ∼97 % for both; 40-year survival 89.9 % vs 81.9 %; p = 0.027). Survival did not, however, vary with residential remoteness. Conclusion: Adults with severe lesions, particularly single-ventricle physiology, remain at high risk of premature mortality. Patients managed in Sydney/Melbourne had better survival, possibly reflecting the influence of long-established specialist ACHD programs, although residual confounding cannot be excluded. Urban-rural outcome parity suggests that Australia's centralised care model mitigates geographical barriers.