Effects of Multipoint Pacing CRT-D on Neurohormonal Activation.

Cardiac resynchronization therapy (CRT) is limited by a high proportion of non-responders. Pacing activation from multiple separated left ventricular (LV) sites might improve the depolarization pattern, thereby promoting more physiological activation. To explore the effect of MPP on cardiac neuro-hormonal activity, the investigators will enroll approximately 30 patients who already underwent CRT-D implantation with a quadripolar LV lead connected to a device capable of MPP. This pilot study will have a randomized, double-blind, cross-over design. Patients will be randomized to receive either standard biventricular pacing (MPP-OFF) or MPP (MPP-ON) within 4-6 months following the implantation procedure. Each subject will crossover to the other study group after three months. The baseline evaluation should be acquired prior to the device being programmed to the randomized setting. Repeat evaluations will be performed at the end of each 3 month crossover period. Participation in this study will last approximately 6 months. Patients, as well as investigators other than the EP physicians, will be blinded to the pacing mode.