Prophylactic catheter ablation for the prevention of defibrillator therapy

Abstract

Background: For patients who have a ventricular tachyarrhythmic event, implantable cardioverter-defibrillators (ICDs) are a mainstay of therapy to prevent sudden death. However, ICD shocks are painful, can result in clinical depression, and do not offer complete protection against death from arrhythmia. We designed this randomized trial to examine whether prophylactic radiofrequency catheter ablation of arrhythmogenic ventricular tissue would reduce the incidence of ICD therapy.

Methods: Eligible patients with a history of a myocardial infarction underwent defibrillator implantation for spontaneous ventricular tachycardia or fibrillation. The patients did not receive antiarrhythmic drugs. Patients were randomly assigned to defibrillator implantation alone or defibrillator implantation with adjunctive catheter ablation (64 patients in each group). Ablation was performed with the use of a substrate-based approach in which the myocardial scar is mapped and ablated while the heart remains predominantly in sinus rhythm. The primary end point was survival free from any appropriate ICD therapy.

Results: The mortality rate 30 days after ablation was zero, and there were no significant changes in ventricular function or functional class during the mean (+/-SD) follow-up period of 22.5+/-5.5 months. Twenty-one patients assigned to defibrillator implantation alone (33%) and eight patients assigned to defibrillator implantation plus ablation (12%) received appropriate ICD therapy (antitachycardia pacing or shocks) (hazard ratio in the ablation group, 0.35; 95% confidence interval, 0.15 to 0.78, P=0.007). Among these patients, 20 in the control group (31%) and 6 in the ablation group (9%) received shocks (P=0.003). Mortality was not increased in the group assigned to ablation as compared with the control group (9% vs. 17%, P=0.29).

Conclusions: In this randomized trial, prophylactic substrate-based catheter ablation reduced the incidence of ICD therapy in patients with a history of myocardial infarction who received ICDs for the secondary prevention of sudden death. (Current Controlled Trials number, ISRCTN62488166 [controlled-trials.com].).

Figure 1. Kaplan–Meier Estimate of the Primary End Point of Survival Free from ICD Therapy

ICD denotes implantable cardioverter–defibrillator.

Figure 2. Hazard Ratios and 95% Confidence Intervals for Subsequent ICD Therapy According to Subgroup

The chart shows hazard ratios (black diamonds) with 95% confidence intervals (horizontal lines) and P values for the interaction between the treatment effect and each subgroup variable. Because of the limited number of patients in certain subgroups, wide confidence intervals are noted. The dashed vertical line indicates the hazard ratio for the study entire population. NYHA denotes New York Heart Association, and ICD implantable cardioverter–defibrillator.

Figure 3. Kaplan–Meier Estimates of Secondary End Points

ICD denotes implantable cardioverter–defibrillator.

Figure 4. Effect of Substrate Ablation on Ventricular Function

The left ventricular ejection fractions (LVEF) at baseline and at 3-month and 12-month follow-up visits are shown for the ablation (blue) and control (red) groups. To assess a preferential negative effect on function in the most severely dysfunctional ventricles, results are also shown for the subgroups with an LVEF of 30% or less and an LVEF of 20% or less. The numbers of patients analyzed (those for whom echocardiographic data were available) are shown above the vertical bars, which indicate the standard deviation.