Value of VT Ablation Prior to ICD Placement

Abstract & Commentary

By John P. DiMarco, MD, PhD Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.

Source: Kuck K-H, et al, for the VTACH study group. Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): A multicentre randomized controlled trial. Lancet. 2010;375:31-40

The ventricular tachycardia ablation in coronary Heart Disease (VTACH) study tested the hypothesis that mapping and prophylactic catheter ablation of ventricular tachycardia prior to implantable cardioverter defibrillator (ICD) insertion in patients with hemodynamically stable ventricular tachycardia (VT) would improve clinical outcomes. VTACH was a multicenter, randomized trial conducted in 16 European centers. Patients were eligible for inclusion if they had at least one clinical episode of documented, stable VT, coronary artery disease with prior myocardial infarction, and an ejection fraction £ 50%. The clinical VT could not have caused cardiac arrest or syncope, and the measured blood pressure during VT had to be > 90 mmHg. Unstable patients, or those with other contraindications to catheter ablation, were excluded. Patients were randomized in a 1:1 ratio to either VT ablation followed by ICD implantation or ICD implantation alone. VT ablation was guided 3D electroanatomical or non-contact mapping, entrainment mapping, and responses to stimulation. Scar mapping and exclusion was also permitted. Patients in both groups received an ICD provided by a single manufacturer to allow uniform data collection. The ICD programming consisted of a VF zone with a cutoff rate of 200 bpm to 220 bpm and a VT zone with a cutoff cycle length that was 60 m/sec longer than the cycle length of the slowest documented VT. Antiarrhythmic drug use was discouraged in general but permitted at the investigator's discretion.

The primary endpoint for the study was the time from ICD implant to recurrence of any sustained VT or VF. Secondary endpoints were survival free of serious clinical events, the number of appropriate ICD interventions, and quality of life as measured by the SF-36 general health survey.

The 16 participating centers enrolled 110 patients in VTACH. Three enrolled patients were excluded, leaving 107 patients in the final study population. At initial electrophysiologic study, monomorphic VT was induced in 94 of these 107 (88%) of patients. Fifty-two patients were randomized to receive catheter ablation. However, seven of these patients did not complete the ablation procedure. Two had intra-procedural events (transient ST segment elevation or a transient cerebral ischemic event), two had no inducible VT and no scar suitable for modification was identified, one had access failure, one had a technical problem, and one refused ablation. Among the 45 patients who received VT ablation, 3D contact or non-contact mapping was used in 43 patients and conventional entrainment mapping in two patients. Three patients received repeat ablation procedures approximately two months after the initial procedure. Among the 55 patients in the ICD group, 12 patients eventually crossed over to VT ablation. The mean time to cross-over was 219 days after the ICD implant. Antiarrhythmic drugs were used sporadically in both groups. At one year, 12 of 46 patients in the ablation group (26%) and 13 of 48 patients in the control group (27%) were on amiodarone. The first recurrence of any ECG or electrogram documented sustained ventricular arrhythmia, VT, or ventricular fibrillation (VF) occurred after a median of 18.6 months in the ablation group and 5.9 months in the control group. By life-table analysis, 59% of the ablation patients and 40% of the ICD-only patients were free from any VT or VF at the 12-month time point. After 24 months, 47% of the ablation patients, compared to 29% of the ICD patients, were free from VT or VF. When subgroups patients with ejection fractions > 30% and/or < 30% were analyzed separately; the former group, with less ventricular dysfunction, showed a significant improvement in survival free from VT or VF, whereas the latter group did not. Secondary endpoints were also analyzed at the 24-month time point. The cardiac hospitalization rate was 33.6% in the ablation group vs. 54.6% in the ICD-only group. The incidence of VT storm was 25% in the ablation group and 30.3% in the ICD only group. There was no difference between groups in mortality, with five deaths in the ablation group and four deaths in the control group. Quality-of-life data were available from slightly over half the patients at both 12 and 24 months. There were no significant differences between the two groups in any of the measures.

Kuck et al conclude that prophylactic catheter ablation in patients with hemodynamically stable VT should be considered along with defibrillator implantation in patients, particularly if the left ventricular ejection fraction is > 30%.

Commentary

The results of the VTACH study illustrate both the benefits and problems of catheter ablation for ventricular tachycardia. It should be noted that the patients in VTACH were good candidates for catheter ablation. They had hemodynamically stable clinical episodes of ventricular tachycardia so induction and mapping of the tachycardia was highly probable. The results show that catheter ablation, performed by experienced operators, did decrease the frequency of VT or VF recurrence. However, more than half of the ablation patients still had at least one VT or VF episode by two years of follow-up even though some of them were also treated with antiarrhythmic drugs. Other studies using amiodarone or sotalol, as well as some investigational antiarrhythmics have shown that ICD therapy frequency can be decreased by prophylactic drug therapy. This study would have been more clinically relevant if it had compared catheter ablation to antiarrhythmic therapy in patients receiving ICDs for secondary prevention. Unfortunately, neither catheter ablation nor drug therapy is reliable enough to eliminate the placement of an ICD in patients with hemodynamically significant, sustained arrhythmias, and both approaches should be looked at as beneficial adjuncts to, rather than replacements for, ICD therapy.

Techniques for catheter ablation of VT continue to evolve. As of yet, the benefits of an early ablation strategy are not great enough to justify a recommendation that prophylactic VT ablation be considered for all patients as proposed by VTACH investigators. Decisions about either ablation or drug therapy should be individualized based on arrhythmia frequency, the ability of antitachycardia pacing to terminate arrhythmias without symptoms, and patient preferences.