SMASHing Ventricular Tachyarrhythmias: Can Ablation Prevent Implantable Cardioverter-Defibrillator Events?

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SMASHing Ventricular Tachyarrhythmias: Can Ablation Prevent Implantable Cardioverter-Defibrillator Events?

Prophylactic, substrate-guided ablation of LV scars reduced the risk for subsequent VT in patients with ICDs for post-MI arrhythmias.

Implantable cardioverter-defibrillator (ICD) therapy reduces mortality in patients with decreased LV function, coronary artery disease, and ventricular arrhythmias (Journal Watch Cardiology Dec 31 1998) by terminating spontaneous ventricular arrhythmias, not by preventing them. However, ICD shocks may cause considerable psychological and other morbidity, and arrhythmias may cause syncope. Limited trial data suggest that antiarrhythmic agents reduce recurrence of ventricular arrhythmias; however, the potential toxicity of these agents has limited their use to treatment of individuals who experience frequent ICD shocks, rather than prophylaxis of arrhythmias.

In the Substrate Mapping and Ablation in Sinus Rhythm to Halt Ventricular Tachycardia (SMASH-VT) trial, patients who received an ICD after spontaneous or induced ventricular tachycardia (VT) following an MI were randomized to either VT ablation or standard clinical care. Ablation was performed using a scar voltage map, eliminating the need to induce and map VT and allowing ablation in nearly all patients randomized to the procedure. In 128 patients followed for a mean of 22 months, 12% of those assigned to ablation had a VT or ventricular fibrillation event, compared with 33% of those assigned to standard care (P=0.007). In a secondary analysis that excluded antitachycardia pacing events (i.e., ICD shocks only), shock incidence was also decreased in the ablation group (9%, vs. 31% in the control group; P=0.003). Mortality did not differ significantly between the two groups.

Comment: Ventricular-tachycardia ablation has traditionally been used for secondary prevention after an implanted cardioverter-defibrillator-terminated VT. In this study, VT ablation was beneficial before ICD-terminated arrhythmias occurred in patients with prior MI. However, as the author of an accompanying editorial cautions, prophylactic VT ablation should not be widely adopted in patients with ICDs until more data are available, especially data directly comparing VT ablation with newer, more aggressive modes of antitachycardia pacing and anti-arrhythmic agents.

— Mark S. Link, MD

Published in Journal Watch Cardiology December 26, 2007