 A suboptimal level of resynchronization cardiac resynchronization therapy CRT achieved in many patients with actual standards and techniques based on tissue-Doppler echocardiography could be more effective to obtain better CRT results. Eligible patients who successfully received atrioventricular AV junction ablation and biventricular BiV pacing are randomised to a comparison between a strategy of right ventricular RV apical pacing with delayed CRT based on clinical indications with a strategy of early optimal CRT based on an echocardiographic stratification. 