Comparison of Cardiac Resynchronisation Therapy (CRT) Response Using High Frequency (HF) - ECG or Q-LV Guided Optimisation for Left Ventricular, Pacing Site.

Inclusion Criteria: • Eligible for implantation of a CRT-D device according to published relevant ESC and CCS guidelines; In sinus rhythm; NYHA class II, III or IV Have reviewed, signed and dated an informed consent. Age 18 Exclusion Criteria: 1. Previous implant with a pacemaker, an ICD or a CRT device. (except upgrade from single chamber ICD with a fully functional defibrillation lead) not under recall or surveillance); 2. Persistent atrial arrhythmias (or cardioversion for atrial fibrillation) within the past month; 3. Ventricular tachyarrhythmia of transient or reversible causes such as acute myocardial infarction (MI), digitalis intoxication, drowning, electrocution, electrolyte imbalance, hypoxia or sepsis, uncorrected at the time of the enrolment; 4. Incessant ventricular tachyarrhythmia; 5. Unstable angina, or acute MI, Coronary Artery Bypass-Grafting (CABG), or Percutaneous Coronary Intervention (PCI) within the past 4 weeks; 6. Correctable valvular disease that is the primary cause of heart failure; 7. Indication for valve repair or replacement; 8. Recent Cerebro-Vascular Accident (CVA) or Transient Ischemic Attack (TIA) (within the previous 3 months); 9. On transplant waiting list; 10. Previous heart transplant; 11. Already included in another clinical study that could confound the results of this study; 12. Life expectancy less than 1 year; 13. Inability to understand the purpose of the study; 14. Unavailability for scheduled follow-up or refusal to cooperate; 15. Age of less than 18 years; 16. Pregnancy; 17. Drug addiction or abuse; 18. Under guardianship.