Emergency and Non-Referral Admissions as Predictors of Hospital Mortality Among Adults with Congenital Heart Diseases: A Nationwide Claim-Based Registry Study in Japan.

Background: Improved pediatric cardiac care has markedly increased the adult congenital heart disease (ACHD) population worldwide, creating new clinical and healthcare delivery challenges. However, nationwide evidence on predictors of acute outcomes in ACHD patients, particularly the impact of disrupted specialist care under universal healthcare systems, remains limited. Methods: We conducted a retrospective analysis using Japan's nationwide administrative database from 2013 to 2022, evaluating hospital admissions of ACHD patients aged ≥15 years. Patients were categorized into surgical, catheter-based, and medical treatment groups. Multilevel logistic regression models identified predictors of in-hospital mortality, including emergency and non-referral admissions as indicators of impaired continuity of specialist care. Results: A total of 27,754 admissions were analyzed (median age 59 years; 49% male). Emergency admissions accounted for 35.2%, non-referral admissions for 9.9%, and overall in-hospital mortality was 5.0%. Older age, admission to non-ACHD centers, higher CHD complexity, emergency admissions, and non-referral admissions were independently associated with increased mortality. In addition, older age, CHD complexity, and admission to non-ACHD centers predicted emergency and non-referral admissions. Conclusions: These findings show persistent gaps in specialist care continuity for ACHD patients despite universal healthcare coverage and support the need for integrated ACHD care networks to improve outcomes in this aging population in Japan.