Impact of intraventricular electrical activation in resynchronization therapy. We seek to evaluate the impact of Cardiac Resynchronization Therapy (CRT) on electrical activation of the Left Ventricle (LV). The first goal of the study is to evaluate if CRT is able to decrease the heterogeneity of LV activation in heart failure patients. A second goal is to evaluate the electrical determinant of clinical response to CRT using invasive and non-invasive mapping technology.

Comprehensive study, prospective, monocentric and cohort study.

Biventricular pacing is an effective therapy to improve end stage heart failure patients, however up to 30% of patients are unresponsive to this therapy. Among others, optimization of Left Ventricle (LV) pacing site location is critical to optimize response to Cardiac Resynchronization Therapy (CRT). Whether a better comprehension of baseline LV electrical activation can help to determine optimal LV lead location remains to be investigated.

After informed consent patients are included in the sudy. Day 1: CRT device is implanted under general anesthesia in a conventional fashion. The coronary sinus leads will be implanted guided by the acute hemodynamic response (+(dP/dt)max) using a RADI guide wire. After device implantation, a steerable mapping catheter will be inserted in the LV cavity to build a tridimensional activation map of the LV. This map will be obtained with and without CRT. From these maps different parameters describing LV activation will be measured and compared between patients with and without CRT. Quantitative parameters: Global LV activation time (LVATG) (primary outcome); septal activation time (LVTAS); Global intra-LV dispersion time and Qualitative parameters: presence of intraLV line of block, area of late activation. Day 5±2: A non-invasive map of the LV will be recorded with the CardioInsight ® system with and without CRT. The same parameters will be measured and compared with those obtained with invasive mapping. A 3 and 6 months follow-up visit including clinical, biological evaluation (NYHA status, 6-min walking test, BNP) of the patients will be performed with an additional transthoracic echocardiography at 6 months.

Inclusion Criteria:

• Adult (aged 18 or above)
• Sinus rhythm
• Patient must have signed informed consent
• Cardiac insufficiency of whatever cause (ischemic or non-ischemic)
• Patient eligible for implantation of a ventricular resynchronization device or patient with a ventricular resynchronization device having a procedure of ventricular tachycardia ablation
• Left ventricular ejection fraction <35%
• NYHA Class II to IV with optimal medical treatment
• Patient covered by national healthcare insurance

Exclusion Criteria:

• Pregnant woman
• Sequel of transmural myocardial infarction