Cardiac resynchronization therapy (CRT) is one of the lastest recommended treatments in patients with refractory symptomatic chronic heart failure with reduced ejection fraction (HFREF). Despite clear guidelines 20 to 40 % of implanted patients are not clinically ameliorated. They are called the "non responders". Patient selection seams to be one of the key to improve the efficiency of CRT. This protocol try to assess positive predictive factors to CRT by a multimodal approach.