Participants undergo general anesthesia, and vascular access is obtained in the x-ray catheterization lab. Next the participant is transferred into the MRI scanner where a focused MRI examination is performed. Catheters are then guided into the heart chambers using real-time MRI guidance to perform conventional cardiac catheterization steps. If time allows, additional research MRI is performed before the participant is returned to the x-ray catheterization lab. If any MRI guided catheterization steps are unsuccessful, the clinically indicated step is performed after the participant returns to the x-ray catheterization lab using conventional x-ray guided pictures.