Risk of Ventricular Tachyarrhythmic Events in Patients Who Improved Beyond Guidelines for a Defibrillator in MADIT-CRT

Abstract

Objectives: This study assessed the arrhythmic risk of cardiac resynchronization therapy (CRT) patients who improved beyond Heart Rhythm Society/European Society of Cardiology guidelines for an implantable cardioverter-defibrillator (ICD) (ischemic cardiomyopathy: left ventricular ejection fraction [LVEF] >35% or New York Heart Association [NYHA] functional class I and if LVEF was 31% to 35%; nonischemic cardiomyopathy: LVEF >35% or NYHA functional class I and if LVEF was ≤35%).

Background: It is currently unknown whether protection with a defibrillator is still warranted in patients who respond to CRT.

Methods: This study compared the risk of ICD therapy for any ventricular tachyarrhythmia (VTA) and for fast VTA (≥200 beats/min) among patients implanted with a CRT with a defibrillator (CRT-D) in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy) (N = 734) who improved at 1 year beyond guideline recommendations for primary ICD therapy (group A) with those who remained within guideline recommendations for an ICD at 1 year (group B).

Results: Most patients implanted with a CRT-D device improved at 1 year beyond guideline indications for an ICD (90%). Multivariate analysis showed lower risks for any VTA and fast VTA among group A patients versus group B patients (57% risk reduction; p = 0.0006 and 46% risk reduction; p = 0.068, respectively). However, the 2-year rates of any VTA and fast VTA among CRT patients who improved beyond guidelines indications for an ICD was still substantial (VTA: 13% and 29%, and fast VTA: 7% and 16%, respectively).

Conclusions: Most patients with mild heart failure implanted with a CRT device experience an improvement in left ventricular function and/or NYHA functional class beyond guideline recommendations for primary ICD therapy. However, despite this pronounced CRT response, there remains a substantial VTA risk, and protection with a defibrillator may still be warranted in this population.

Keywords: cardiac resynchronization; heart failure; ventricular arrhythmias.