of sudden death, 4 mortality from chronic heart failure exacerbations, 5,6 and admission to the intensive care unit (ICU) or emergency room 30 days before death than in patients with cancer. 7 These findings support an approach that focuses on the clinical status of patients in the last phase of life and on the circumstances surrounding their death, and are important data for developing a framework for medical and end-of-life (EOL) care for patients with ACHD. However, most studies to date have been singlecenter studies with small sample sizes 8,9 and limited generalizability to the growing population of patients with S urvival among patients with congenital heart disease (CHD) has increased due to advances in cardiovascular interventional techniques and therapy, with many patients reaching adulthood. 1 Reports indicate that in 2023 an estimated 500,000 individuals have adult CHD (ACHD) in Japan. 2 As the number of patients with ACHD has increased, the focus has primarily shifted to improving treatment outcomes, life expectancy, and quality of life.With improvements in the care of patients with ACHD, their life expectancy has also improved. Changes in patterns of death have also been observed, 3 with higher rates