Investigation of Transvenous Versus Epicardial Left Ventricular Stimulation Technique

This clinical trial is a multicenter, prospective, randomized, parallel, open study designed to compare epicardial left ventricular pacing to transvenous left ventricular pacing for delivering cardiac resynchronization therapy. After a pre-implant baseline evaluation, patients will be randomized in a 1:1 fashion to one of two groups: * Control group: resynchronization via a transvenous left ventricular lead (TVN CRT); * Treatment group: resynchronization via an epicardial left ventricular lead (EPI CRT). All patients taking part in this study will undergo the implantation of a CRT device with or without ICD back-up (depending on the physician's decision), with right atrial and right ventricular transvenous leads. Patients will attend protocol scheduled visits before implant (pre-implant baseline evaluation), and post-implant: before hospital discharge, 6 weeks post-implant (optional visit), 3 months (optional visit), and 6 months after implant, time of study termination.