Left Atrial Volume as Predictor for Arrhythmic Events and CRT Response

Inclusion Criteria: * Patient with left ventricular ejection fraction ≤ 35%, II, III or IV NYHA Class, even if optimal medical therapy. * Patients with standard indication to CRT according current guideline, sinus rhythm at implantation, LBBB and QRS duration \>= 120 ms * Patients who will undergo to a new CRT-defibrillator system implantation * Patients who are able to understand and sign the informed consent * Patients who are able to attend all required follow-up visits at the study centerfor 24 months Exclusion Criteria: * Age \< 18 years * Women who are pregnant or who are planning to become pregnant * Patients with permanent Atrial Fibrillation or persistent Atrial Fibrillation in the 90 days preceding the implantation * Patients with organic mitral valve disease * Patients with prosthetic heart valves * Patients who will undergo to upgrading from other devices (PM or ICD) to CRT, heart transplantation, patients with CRT devices