CRT-D combines biventricular pacing with an implantable defibrillator. It delivers synchronized electrical impulses to the right ventricle and left ventricle (via coronary sinus lead) to correct electrical dyssynchrony, improving coordinated ventricular contraction. The defibrillator component continuously monitors rhythm and delivers antitachycardia pacing or shocks to terminate life-threatening ventricular tachyarrhythmias.
Indications:
CRT-D is indicated in patients with heart failure with reduced ejection fraction (≤35%), sinus rhythm, wide QRS (≥130 ms, especially LBBB morphology), and NYHA class II–IV symptoms despite optimal medical therapy, who also have an indication for defibrillator therapy (primary or secondary prevention of sudden cardiac death). It improves symptoms, exercise capacity, reduces heart-failure hospitalizations, and lowers mortality.
