1. Patients with complex CHD including cyanotic heart disease, subaortic right ventricle physiology, single ventricle physiology, Ebstein anomaly with ≥ moderate tricuspid regurgitation and patients with Tetralogy of Fallot (including those with pulmonary atresia of Fallot type or double-outlet right ventricle of Fallot type) and either residual free pulmonary regurgitation or left- or right ventricular systolic dysfunction (demonstrated by echocardiography or cardiac MRI).