Beyond Binary Recurrence: ICD Therapy Burden Reduction as a Marker of Success of Catheter Ablation for Ventricular Tachycardia in Ischemic Heart Disease; and the Association of Scar Metrics with Arrhythmia Recurrence

Technical Summary: Beyond Binary Recurrence in VT Ablation for Ischemic Heart Disease

Problem Statement
Catheter ablation (CA) is an established treatment for ventricular tachycardia (VT) in patients with ischemic cardiomyopathy (ICM). However, current clinical success metrics often rely on a binary definition of "freedom from recurrence." The authors argue that this binary outcome may not fully capture the clinical benefit of the procedure, particularly given that patients often prioritize the reduction of implantable cardioverter-defibrillator (ICD) therapies (shocks and anti-tachycardia pacing) over the complete elimination of arrhythmia. Furthermore, the role of the underlying arrhythmogenic substrate—specifically scar metrics derived from high-density electroanatomical mapping (HD-EAM)—in predicting post-ablation outcomes remains uncertain, especially when compared to traditional clinical parameters like VT cycle length (VT-CL) or left ventricular ejection fraction (LVEF).

Methodology
The study is a retrospective, single-center observational analysis of 90 consecutive patients with ICM who underwent CA for sustained VT or VT storm between January 2017 and December 2025.

• Population: All patients had ICDs or cardiac resynchronization therapy defibrillators (CRT-Ds) with at least 12 months of device data available both pre- and post-ablation.
• Procedural Details: Procedures utilized 3D electroanatomical mapping (CARTO system) with high-density mapping catheters (Pentaray or Octaray). Endocardial substrate mapping defined scar as bipolar voltage ≤0.5 mV. Scar area was quantified in cm², and scar burden was calculated as the percentage of scar area relative to the total mapped myocardial area.
• Endpoints:
  • Primary: VT recurrence within 12 months, defined as sustained VT (≥30 seconds), appropriate ICD shocks, or appropriate anti-tachycardia pacing (ATP).
  • Secondary: Change in ICD therapy burden (shocks and ATP episodes) comparing the 12 months pre-ablation to the 12 months post-ablation.
• Statistical Analysis: The study employed univariable and multivariate logistic regression to identify predictors of recurrence (including age, NYHA class, LVEF, VT-CL, VT storm history, and scar metrics). Receiver Operating Characteristic (ROC) analysis was used to establish thresholds for scar area and scar burden.

Key Results

• Recurrence Rates: 37 patients (41.0%) experienced VT recurrence within 12 months.
• ICD Therapy Reduction: Despite the high recurrence rate, CA resulted in a statistically significant reduction in ICD therapy burden across the entire cohort.
  • Median shock burden decreased from 2.0 (IQR 1.0–6.0) pre-ablation to 0.0 (IQR 0.0–1.0) post-ablation (p<0.001).
  • Median ATP burden decreased from 8 (IQR 2.25–21.3) to 0.0 (IQR 0.0–5.0) post-ablation (p=0.001).
  • Notably, even among the 37 patients with recurrence, median shock burden decreased significantly (from 4 to 1.0, p=0.001), representing a 46.4% reduction in total shock burden for this subgroup.
• Predictors of Recurrence:
  • Scar Metrics: Patients with recurrence had significantly larger mean scar areas (76.1 ± 36.3 cm² vs. 57.1 ± 31 cm²; p=0.012) and higher scar proportions (35% ± 12% vs. 27% ± 12%; p=0.008).
  • Thresholds: ROC analysis identified a scar proportion threshold of ≥28.5% as a predictor of recurrence (Sensitivity 74%, Specificity 58%, OR 3.99). In multivariate analysis, a scar proportion ≥28.5% remained an independent predictor (HR 2.8, p=0.045).
  • LVEF: Mean LVEF was lower in the recurrence group (27.8% vs. 32.6%; p=0.024). However, in multivariate analysis adjusting for scar burden, LVEF was not an independent predictor, suggesting it may be a surrogate for scar substrate.
  • Non-Predictors: Clinical VT-CL (≤350 ms vs. >350 ms), history of VT storm, and NYHA functional class were not significantly associated with recurrence.
• Timing: The median time to recurrence was 33 days, with 48.6% of recurrences occurring within the first 30 days.

Significance and Claims
The paper posits that the success of VT ablation in ICM should be evaluated through a broader, patient-centered framework that includes the reduction of arrhythmia and ICD therapy burden, rather than relying solely on binary recurrence. The authors claim that:

1. Clinical Benefit Beyond Cure: Significant clinical benefit exists even in patients who experience recurrence, evidenced by the substantial reduction in shock and ATP burden. This supports using "arrhythmia burden" as a valid metric for procedural success.
2. Substrate as the Primary Predictor: Substrate characteristics, specifically the quantified scar burden derived from high-density mapping, are superior predictors of recurrence compared to traditional clinical metrics like VT-CL or storm history.
3. Risk Stratification: A scar proportion threshold of ≥28.5% serves as a potential tool for pre-procedural risk stratification, identifying patients at higher risk for recurrence who might benefit from alternative management strategies or more aggressive substrate modification.

The authors conclude that while substrate burden and LV function are associated with recurrence, the reduction in ICD therapies validates the utility of ablation even when complete freedom from arrhythmia is not achieved. They emphasize the need for further studies to validate these scar thresholds and to evaluate patient-centered outcomes, including quality of life.