ECG before and after the CRT placement. Before the CRT placement (A), QRS duration was prolonged as 174 msec. In addition, ECG showed the prolonged PR interval and complete left bundle branch block (CLBBB). After the CRT placement (B), the QRS duration was shortened to 152 msec. In addition, PR interval was shortened and CLBBB changed to complete right bundle branch block (CRBBB).