Biventricular pacing (BiVP) reverses intraventricular conduction delay (IVCD) and left ventricular (LV) dysfunction in dilated cardiomyopathy (DCM). BiVP improves LV function and cardiac index (Cl) at no energy cost. In the MIRACLE trial, in patients with DCM, IVCD and LV ejection fraction <35%, demonstrated improved subjective and objective measures of exercise tolerance and cardiac function with BiVP. BiVP benefits many, but selection criteria are not fully developed, and 30% of recipients are "nonresponders," at a cost of more than $2 billion/year. Preliminary data suggest that BiVP can benefit patients with low output states after cardiac surgery. We plan to assess surgical application of BiVP while assessing mechanisms of action and optimization. We will randomize 190 cardiac surgery patients with LV dysfunction preoperatively to paced and standard of care groups. BiVP will be optimized and continued postoperatively until patients are stable. BiVP will be assessed transiently in all patients at three time points. The primary end point is a 15% improvement in thermal dilution Cl measured in the intensive care unit (ICU). Effects of heart rate, atrioventricular delay, ventricular pacing site, and interventricular delay on Cl will be assessed using a randomized sequence of data collection. Secondary endpoints include incidence of arrhythmias, inotropic support, urine output, weight gain, morbidity, mortality, and ICU costs. These studies are important because of a high probability of clinical benefit. The methods employed will provide precision, breadth of measurement, and range of pacing sites superior to any other setting. The protocol will provide new and important scientific information that will benefit not only surgical patients but also the general population of BiVP recipients.