The purpose of this study is to observe the evolution of the CRTD system with left quadripolar lead, in terms of electrical parameters in all pacing configurations and to evaluate the impact on the clinical outcome.

Cardiac resynchronization therapy (CRT) is limited by a high proportion of non-responders.

Pacing activation from proximal area with a left quadripolar lead might improve the depolarization pattern.

To explore the effect of CRT pacing on cardiac activity, the investigators will enroll approximately 180 patients who already underwent CRT-D implantation with a quadripolar LV lead.

After implant, as clinical practice, the device will be programmed with distal LV pacing configuration, after 6 months in patient non-responders to CRT therapy the pacing configuration will be changed (proximal configuration).

After 12 months in patients non-responders will be changed the pacing configuration again, choosing, if it is possible, a multi point pacing (pacing activation from multiple separated left ventricular (LV) sites).

Inclusion Criteria:

• Be in NYHA II, III or IV functional class with approved standard indication by ESC/EHRA Guidelines
• Successful quadripolar LV lead implant

Exclusion Criteria:

• Less than 18 years of age
• Epicardial Lead
• Life expectancy < 12 months
• Pregnant or are planning to become pregnant during the duration of the investigation

Heart Failure