Impact of Carvedilol and Metoprolol on Inappropriate ICD Therapy in the MADIT-CRT Trial
Do beta-blockers reduce the frequency of inappropriate implantable cardioverter-defibrillator (ICD) therapies in patients with heart failure (HF)?
This was a post-hoc analysis of the MADIT-CRT study, in which 1,790 patients (mean age 65 years) with class I-II HF, ejection fraction ≤30%, and QRS duration ≥130 ms received an ICD with or without cardiac resynchronization therapy (CRT). All patients received optimal pharmacological therapy for HF in accord with conventional guidelines. The primary endpoint of this study was the occurrence of an inappropriate ICD therapy.
One hundred and twenty patients did not receive a beta-blocker, 1,077 received carvedilol, 438 received metoprolol, and 146 received another beta-blocker. An inappropriate ICD therapy occurred in 14% of patients during a mean follow-up of 3.4 years. Compared to metoprolol, the use of carvedilol was associated with a 46% lower probability of an inappropriate ICD shock and a 34% lower probability of an inappropriate antitachycardia pacing therapy. Compared to metoprolol, an inappropriate ICD therapy triggered by atrial fibrillation was 50% less likely to occur in patients receiving carvedilol.
The authors concluded that compared to metoprolol, carvedilol significantly reduces the risk of inappropriate ICD therapies in patients with HF.
No prior studies have compared the effects of different beta-blockers on inappropriate ICD therapies. Carvedilol blocks alpha-1, beta-1, and beta-2 receptors, whereas metoprolol selectively blocks beta-1 receptors. This might explain the higher efficacy of carvedilol for preventing inappropriate ICD therapies. Regardless of the explanation, the results indicate that carvedilol is the beta-blocker of choice in patients with HF who have an ICD.
Keywords: Transcription Factors, Propanolamines, Cardiac Resynchronization Therapy, Heart Diseases, Carbazoles, Flavins, Heart Failure, Luciferases, Receptors, Adrenergic, beta-1, Metoprolol, Defibrillators, Implantable
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