CRTD is an advanced form of pacing therapy, CRT is a triple-chamber pacemaker placement, also called cardiac resynchronization therapy, while CRTD is a defibrillation function added to cardiac synchronization. These patients are at risk for potentially malignant ventricular arrhythmias. The implantation of CRTD can artificially synchronize the contraction of the right and left ventricles, and in case of ventricular tachycardia and ventricular fibrillation, defibrillation treatment can be performed at the first time. This is a strong indication for CRTD implantation if the patient also has bradycardia.