Effect of Cardiac Resynchronization Therapy on the Risk of First and Recurrent Ventricular Tachyarrhythmic Events in MADIT-CRT

Study Questions:

Does cardiac resynchronization therapy (CRT) prevent ventricular tachycardia/ventricular fibrillation (VT/VF)?


This was a substudy of the MADIT-CRT trial, in which 1,820 patients with dilated cardiomyopathy, New York Heart Association class I-II heart failure, ejection fraction ≤30%, and QRS duration ≥130 ms were randomly assigned to treatment with either an implantable cardioverter-defibrillator (ICD) plus CRT (CRT-D) or an ICD without CRT in MADIT-CRT. The primary endpoint was the occurrence of an appropriate ICD therapy for VT/VF with a rate of 180 bpm.


CRT-D was independently associated with a 42% reduction in the primary endpoint among patients with left bundle branch block (LBBB), but had no significant effect on the primary endpoint in patients with non-LBBB patients. The risk of a second episode of VT/VF did not change in patients with an LBBB treated with CRT-D, but increased >3-fold in patients with non-LBBB in the CRT-D group. The risk of heart failure or death did not rise after a first episode of VT/VF, but increased approximately 2- to 3-fold after a second or third episode of VT/VF.


CRT-D reduces the risk of VT/VF in patients with an LBBB. CRT-D is associated with a higher risk of recurrent episodes of VT/VF after a first episode in patients with a non-LBBB.


Other studies have demonstrated that the beneficial effects of CRT on echocardiographic parameters are limited to patients with LBBB. The increased risk of recurrent VT/VF after a first event among patients with a non-LBBB in the CRT-D arm may simply reflect progression of the underlying heart disease, rather than a deleterious direct effect of CRT.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Risk, Defibrillators, Heart Conduction System, Ventricular Fibrillation, New York, Tachycardia, Cardiac Resynchronization Therapy, Death, Cardiac Pacing, Artificial, Cardiomyopathies, Heart Failure, Echocardiography

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