MRI studies will be performed in a 1.5 tesla unit. SSFP cine images will be obtained in the short-axis plane encompassing the entire heart. Velocity-encoded cine MR images will be obtained perpendicular to the direction of blood flow in the main pulmonary artery. Volumetric and flow analysis will be performed in a separate dedicated workstation by a radiologist. End-diastolic volume, end-systolic volume, ejection fraction, total ejection fraction and pulmonary regurgitant fraction will be calculated.