Antiarrhythmic Effect of Cardiac Resynchronization Therapy

Study Questions:

What is the effect of the echocardiographic response to cardiac resynchronization therapy (CRT) on ventricular arrhythmias (VAs)?


The authors searched PubMed for studies where they could analyze the following: 1) the effect of CRT defibrillator (CRT-D) versus implantable cardioverter-defibrillator (ICD)-only therapy on VA, 2) the incidence of VA in echocardiographic CRT responders versus nonresponders, and 3) the incidence of VA among CRT nonresponders before and after upgrade from ICD-only status.


Thirteen studies (n = 4,631) included in the meta-analysis showed that patients with CRT had a significantly lower incidence of VA compared with patients with ICD only (odds ratio, 0.754). Thirteen studies (n = 3,667) included in the meta-analysis of VA in CRT responders versus nonresponders showed that responders had a significantly lower risk of VA (odds ratio, 0.436). Three studies included in the comparison of VA in CRT nonresponders before and after upgrade from ICD showed that CRT nonresponders had an elevated risk of VA compared with ICD-only subjects (odds ratio, 1.497).


The authors concluded that CRT may significantly reduce the risk of VA compared with ICDs in patients who meet criteria for CRT. CRT responders have significant reduction in VA compared with nonresponders. CRT nonresponse may significantly increase risk of VA.


While CRT reduces mortality and congestive heart failure hospitalizations, nonrandomized reports showed mixed results in terms of CRT effect on the risk of VAs. Case reports suggested that CRT may trigger VA in some patients. At least a couple studies have suggested that CRT is underutilized in patients who are good candidates for this therapy as much as 30% of the time. It is not clear what the causes are, but the present study highlights the need to increase adherence by pointing to yet another benefit, which may be attributable to CRT: an antiarrhythmic effect. The analyses suggest that the antiarrhythmic effects of CRT may be a function of reverse remodeling reflected in the echocardiographic improvement.

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

Keywords: Anti-Arrhythmia Agents, Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Cardiac Resynchronization Therapy Devices, Defibrillators, Implantable, Echocardiography, Heart Conduction System, Heart Failure, Myocardial Ischemia, Secondary Prevention

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