Due to the success of cardiac surgery in infancy and childhood, starting some 40 years ago and improving ever since, the survival for patients with congenital heart disease has improved dramatically. Over 85% of all patients born with a congenital cardiac defect now survive beyond childhood, often well into adult life. Many of these patients have residual abnormalities, which may be morphological, functional or (most often) both, and these residua tend to change with time.