Substrate-Based Ablation Superior to Ablation Targeting Only Clinical and Mappable Ventricular Tachycardias

Ischemic cardiomyopathy (IC) is a frequent cause of fatal ventricular arrhythmias, many of which are tachycardias caused by scar-related re-entry. For the first time, a randomized trial  demonstrated that in patients with ischemic cardiomyopathy, substrate-based ablation is superior to ablation targeting only clinical and mappable ventricular tachycardias (VT).

The VISTA (Ablation of Clinical Ventricular Tachycardia Versus Addition of Substrate Ablation on the Long Term Success Rate of VT Ablation) trial results were published in the Journal of the American College of Cardiology.

Researchers enrolled 118 patients with IC and hemodynamically tolerable VT at 7 centers. All patients had an implantable cardioverter-defibrillator (ICD) placed before the ablation, and all had experienced “recurrent stable monomorphic VTs that were symptomatic or required ICD therapies” despite treatment with antiarrhythmic drugs (AADs).

Patients in whom VT was accompanied by syncope, loss of consciousness, or cardiac arrest were excluded from the trial. Other exclusion criteria were age <18 years, severe renal insufficiency, left ventricle thrombus, unstable angina, severe aortic stenosis, end-stage heart failure with limited life expectancy, and a history of failed VT ablation.

To determine which method of ablation was more effective in preventing VT recurrence, the researchers randomly assigned patients to 1of 2 treatments: 60 to ablation of clinical and mappable VTs only (clinical VT ablation), and 58 to the more extensive substrate-based ablation, which targeted all abnormal potentials within the scar tissue and was performed during sinus rhythm, rather than during induced VT.

Recurrence of VT during the 12 months following the procedure was the primary end point, which was defined as “any symptomatic arrhythmia or arrhythmia receiving device-based treatment [namely, shock or adenosine triphosphate] or present on clinical evaluation.” Periprocedural complications, post-procedure mortality (through 12 months), and rehospitalization (for causes related to the procedure, arrhythmias, or heart failure) were secondary end points, as was the combined incidence of rehospitalization and mortality.

Although substrate-based ablation aimed to eliminate all abnormal potentials within the scarred area, this objective was notmet in 9 of the 58 patients (16%) randomized to this group. The post-ablation end point for both the substrate and clinical ablation groups was the inability to induce clinical VTs, which was met in all cases.

In both groups, AADs were discontinued after ablation but reinitiated if VT recurred. For a year following ablation, patients were evaluated at 3-month intervals and during symptomatic events. Evaluations were conducted by way of remote monitoring or office visits and included ICD interrogation.

The results demonstrated that, at the 12-month follow-up, the rate of VT recurrence was significantly lower for the group that had been treated with substrate-based ablation than for the group that had undergone clinical VT ablation (15.5% vs 48.3%; log-rank P<.001); median  time to VT recurrence was 7 months and 2.5 months, respectively. Fewer patients required AADs after substrate ablation than after clinical ablation (12% vs 58%; P<.001).

The rate of post-ablation rehospitalization was also lower with substrate-based ablation: 12.1% vs 32% (P=.014), as was 12-month mortality (8.6% vs 15.0%; log-rank P=.21). When the secondary end points of rehospitalization and mortality were combined, incidence was significantly lower with substrate-based than with clinical VT ablation (20.7% vs 46.7%; P=.003).

Periprocedural complication rates were similar for the 2 groups (P=.61), with 3 pericardial effusions in the substrate ablation group, and 2 effusions and 1 arteriovenous fistula in the clinical ablation group.

As the authors noted, the study “suggests that a larger area of scar tissue must be ablated to reduce recurrence from any VTs in patients with IC and stable clinical VTs.” Further studies are needed to compare the various methods of substrate-based ablation with respect to efficacy in patients with IC.

Reference

1. Di Biase L, Burkhardt JD, Lakkireddy D, et al. Ablation of stable VTs versus substrate ablation in ischemic cardiomyopathy: the VISTA randomized multicenter trial. J Am Coll Cardiol. 2015;66(25):2872-82. http://dx.doi.org/10.1016/j-jacc.2015.10.026.