Mitral Insufficiency Reduction With Biventricular Pacing

The chronic effect of CRT pacing on the degree of MR in pts with severe-to-moderate or severe functional MR. The treatment being studied is CRT pacing therapy with standard of care LV lead placement. Patients will be randomized to CRT pacing ON vs. OFF and followed for a total of up to 8 months. This includes two 3-month crossover periods for each pacing modality (CRT ON and CRT OFF) and a 6-week washout period between these periods.