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Extensive ablation for ventricular tachycardia (VT) can be avoided with a novel strategy using voltage-independent functional mapping of critical sites prone to re-entry to target more limited regions for ablation, according to study results published in Circulation.
Conventional substrate ablation strategies for VT lack specificity in identifying the VT isthmus and are dependent on extensive homogenization of the tissue to prevent reentry. Researchers created a novel substrate strategy for VT ablation targeting deceleration zones (DZ), regions with specific isochronal crowding (>3 isochrones within a 1 cm radius having slowed conduction velocity), as targets for ablation. To assess the effect of this novel VT ablation strategy on VT recurrence and mortality, consecutive patients with scar-related VT (n=120) were enrolled in the VT Ablation Registry and underwent ablation using the DZ-targeted strategy. A total of 144 DZ-targeted ablation procedures were performed, with 22 patients requiring redo or repeat ablation procedures.
Prior to the ablation procedure, clinical morphology of the patients’ VT and hemodynamic tolerance were assessed. Isochronal late activation mapping (ILAM) was used to manually confirm the primary DZ regions and guide targeting of the ablation. Following identification of the primary DZ epicardial mapping (or endocardial mapping when necessary), ablation was performed. ILAM was recorded in sinus rhythm, with intrinsic QRS activation when possible, to enable comparison with successful ablation to DZ locations to asses accuracy.
The results of the study showed that the median targeted area was 31.5% of the scar area for endocardial ablation, 14.6% of the scar area for epicardial ablation, and 18.4% of the scar area in patients who received combined epi-endo mapping and ablation of low-voltage areas. A single primary DZ region was targeted in 37% of cases and 63% were treated with ablation of an additional DZ target (41% of cases involved 1 additional DZ ablation site, 19% involved 2 additional DZ sites, and 3% involved 3 additional sites). The number of sites targeted for ablation was determined at the discretion of the operator based on the induction of additional VT morphology.
Successful termination of VT via the novel DZ-targeted ablation strategy was achieved in 59% of cases. In 42 of the 144 procedures where comparison remapping using intrinsic QRS activation was performed, complete elimination of isochronal crowding was observed in 21% of patients, and reduced isochronal crowding was observed in 74% of patients. The rate of VT recurrence was not statistically lower in patients with complete elimination of isochronal crowding compared with those with a reduction in isochronal crowding (11% vs 26%; P =.35). At follow-up (12±10 months), 70% of patients had no recurrence of VT and overall mortality rate was 12% (4 of the 122 patients).
Limitations of this study included reduced generalizability due to the small sample size and the lack of a control group. Additionally, the high success rates could be in part due to incorporation of epicardial approach and multielectrode catheters. Further, operators were not blinded to voltage map display and conduction slowing, which may have introduced some bias.
The researchers concluded, “Targeted ablation guided by a voltage-independent functional mapping display during baseline rhythm was feasible and effective to expedite the identification of highly arrhythmogenic regions within myocardial scar, obviating the need for extensive ablation.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Reference
Aziz Z, Shatz D, Raiman M, et al. Targeted ablation of ventricular tachycardia guided by wavefront discontinuities during sinus rhythm: a new functional substrate mapping strategy [published online September 19, 2019]. Circulation. doi:10.1161/CIRCULATIONAHA.119.042423
