Subjects will be eligible for enrollment in this study if they are undergoing cardiopulmonary bypass surgery for right or left ventricular surgery or biventricular surgery and (1) have intra-cardiac conduction delay or bundle branch block post-surgery; (2) have echocardiographic evidence of ventricular dyssynchrony; (3) have pre-existing conduction disease or bundle branch block; or (4) have pre-existing ventricular dyssynchrony.