In order to be eligible to participate in this study, a subject must meet all of the following criteria: adult age and mentally competent; and Tetralogy of Fallot; and right ventricular dysfunction, defined as right ventricular ejection fraction 50% or lower as measured by Cardiovascular Magnetic Resonance Imaging (CMR). Not more than moderate tricuspid or pulmonary regurgitation or more than moderate pulmonary stenosis as measured by CMR or echocardiography.