Advances in surgical and medical care have led to improved outcomes in patients with congenital heart disease (CHD). As a consequence, the majority of patients nowadays survives to adulthood (adults with CHD, that is, adult CHD \[ACHD\]) with good quality of life. Despite the surgical success, the morbidity and mortality of ACHD is higher than in the general population and is linked to the development of heart failure (HF) in adulthood. HF occurs in approximately 25% of patients with ACHD, even in those patients in whom the congenital mal-formation has been corrected successfully in childhood. The time course and presentation are heterogeneous owing to variable congenital malformation and limitation of treatment options. ACHD with an anatomic right ventricle as the systemic ventricle (e.g., atrial switch operation in patients with transposition of the great arteries \[TGAs\]) and those with a functional single ventricle (e.g., Fontan circulation) appear to be at higher risk of developing HF. Young age at initial corrective surgery-often in the first 2 years of life-and lack of specific medical therapies can contribute to a high and early demand for heart transplantation in patients with ACHD.