Ventricular Tachyarrhythmia in Patients Improved Beyond Guidelines for ICD in MADIT-CRT
Do patients who respond to cardiac resynchronization therapy (CRT) continue to require protection from implantable cardioverter-defibrillator (ICD)?
This study evaluated 734 patients of 1,820 patient group in the MADIT-CRT trial (Multicenter Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy). All had received CRT with a defibrillator (CRT-D). At time of enrollment in the MADIT-CRT trial, all patients had left ventricular ejection fraction (LVEF) <30%, QRS duration >130 ms, and New York Heart Association (NYHA) Class I or II ischemic or NYHA Class II nonischemic cardiomyopathy. NYHA functional class evaluation was available for all participants. Echocardiogram was obtained before device implantation and at 12 months of follow-up. Device interrogation was performed every 3 months. Those with ischemic cardiomyopathy, defined as improved beyond American Heart Association, American College of Cardiology, Heart Rhythm Society, and European Society of Cardiology guidelines for primary prevention ICD, at 12-month follow-up had LVEF >35% or NYHA Class I with LVEF of 31-35%. Those with nonischemic cardiomyopathy, defined as improved beyond American Heart Association, American College of Cardiology, Heart Rhythm Society, and European Society of Cardiology guidelines for primary prevention ICD, at 12-month follow-up had LVEF >35% or NYHA Class I and LVEF <35%. Primary endpoint was initial occurrence of appropriate ICD therapy for ventricular tachyarrhythmia including ventricular tachycardia or ventricular fibrillation. Secondary outcomes included episodes of fast ventricular tachyarrhythmia (defined as >200 bpm) and the combined endpoint of death and ventricular tachyarrhythmia.
Of the 734 study participants, 657 (90%) improved beyond indication for primary prevention ICD by 12 months of follow-up. In 632 of these patients, LVEF improved to >35%. At baseline, the group that improved had significantly lower creatinine levels, higher systolic blood pressure, smaller cardiac chambers, and higher baseline LVEF than the group that did not improve. The primary endpoint of first occurrence of appropriate ICD therapy for ventricular tachyarrhythmia was significantly lower at 2 years among patients who improved compared with those who did not improve (3% vs. 29%; log-rank p < .001). Episodes of fast ventricular tachyarrhythmia (>200 bpm) were significantly lower at 2 years among those who improved compared with those who did not improve (7% vs. 16%; p = .017). The combined endpoint of death and ventricular tachyarrhythmia was 58% lower (p < .001) in those who improved compared with those who did not improve. In those with ischemic cardiomyopathy who improved, ventricular tachyarrhythmia rate at 2 years was 15% compared with 27% in those who did not improve. In those with nonischemic cardiomyopathy who improved, ventricular tachyarrhythmia rate at 2 years was 11% compared to 32% in those who did not improve.
Patients with CRT-D whose LVEF and/or NYHA functional class improved beyond the current guideline indication for primary prevention ICD may still experience substantial risk of ventricular tachyarrhythmia. At the time of generator replacement, these findings should be considered when counseling patients regarding subsequent device selection (CRT-D vs. CRT pacemaker).
By 12 months following implantation, 90% of patients in this MADIT-CRT subgroup analysis treated with CRT-D experienced improvement in LVEF and/or NYHA functional class beyond the current indication for ICD. Those with improvement had significantly less ventricular tachyarrhythmia than those who did not improve beyond indication for ICD. Nonetheless, the risk for ventricular tachyarrhythmia in those who improved was still substantial, occurring in 13% by 2 years from implantation. Despite improvement from CRT, the findings suggest that CRT-D might still be warranted in these patients at time of generator change. Further studies with prospective randomization are warranted regarding the need for continued ICD therapy in patients with recovery of LVEF.
Keywords: Cardiac Resynchronization Therapy, Ventricular Fibrillation, Arrhythmias, Cardiac, Tachycardia, Ventricular, Defibrillators, Implantable, Pacemaker, Artificial, Stroke Volume, Cardiomyopathies
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