The purpose of this study is to investigate the efficacy of optimized temporary biventricular pacing (BiVP) in patients undergoing open-heart surgery with preoperative LV dysfunction and an intraventricular conduction delay. This study will compare extended temporary biventricular pacing versus standard of care by assessing patients randomized to the two groups, from the conclusion of cardiopulmonary bypass, until the conclusion of pharmacologic circulatory support in the intensive care unit. In addition, effects of biventricular pacing will be tested in all patients, at three time points, using different measures of blood flow. Results from this research will demonstrate whether temporary BiVP improves cardiac output after open-heart surgery and whether ventricular pacing optimization increases cardiac output in this setting. Success would lead to the development of recommendations for use of BiVP postoperatively and would stimulate the development of pacemakers with appropriate features. Our primary hypothesis is that the optimum pacing protocol (POPT) will increase cardiac index (CI) by 15% (from approximately 2.30 to 2.64 L/min/m2) compared to standard of care as measured by thermodilution 12-24 hours postoperatively. Secondary objectives include defining POPT at three time points within 24 hours of surgery. We will examine which forms of cardiac dysfunction benefit from temporary pacing using direct and indirect measures of perfusion and cardiac function. We will also analyze survival, length of stay, incidence of arrhythmias, and cost of postoperative care.