Response of Cardiac Resynchronization Therapy Optimization With Ventricle to Ventricle Timing in Heart Failure Patients

Study Methods * This is a prospective, randomized (simultaneous biventricular (BiV) pacing vs. sequential BiV pacing) study. * Any patient that receives an FDA approved St. Jude Medical (SJM) CRT-D with V-V timing is eligible for enrollment. * At 3 months post enrollment (or at implant for CRT-D replacements), patients screened as non-responders are randomized to either simultaneous or sequential BiV pacing. Patients requiring a replacement CRT-D device that are identified as non-responders to CRT are enrolled at the screening/randomization visit. * Patients are followed for a period of 6 months post randomization: * Enrollment (1 week pre CRT-D implant to \< 2 weeks post CRT-D implant) * Screening/Randomization Visit (3 months post enrollment) * Follow-up Visit (6 months post randomization) * Total # of centers - 80 centers * Sample size - 800 patients screened for CRT non-responders