Cardiac magnetic resonance to evaluate 3-dimensional ventricular substrate depth: Prognostic implications for ventricular tachycardia ablation approach

BACKGROUND: Substrate-based catheter ablation is an effective procedure for scar-related ventricular tachycardia (VT). Endoepicardial access may be considered as the first strategy in cases where epicardial VT is suspected, despite its higher risk of severe complications. Moreover, cardiac magnetic resonance (CMR) is a valuable tool for assessing the arrhythmic substrate and guiding ablation. OBJECTIVE: This study aimed to assess the impact of CMR channel depth on ablation approach selection. METHODS: 51 consecutive patients with left-scar-related VT undergoing exclusive endocardial ablation after CMR in Hospital Clinic (October 2018 to June 2022) were included (72.5% ischemic cardiomyopathy). CMR channel depth was calculated based on the involved layers and the wall thickness of the affected segments. RESULTS: 159 CMR channels were analyzed. In the univariable analysis, both the maximal depth of the channel and epicardial channel presence were the only predictors of VT recurrence (odds ratio 1.85 1.11-3.13, P = .02, and odds ratio 1.22 1.15-1.41, P = .04, respectively). A channel depth cutoff of 7.2 mm predicted VT recurrence with 100% sensitivity, 61.4% specificity, a negative predictive value of 100%, and an area under the curve of 0.81. The presence of an epicardial channel also showed 100% of sensitivity and negative predictive value but a worse specificity (27.27%) and positive predictive value (17.95%) than the maximal channel depth. 1-year VT recurrence rate was 13.7%. CONCLUSION: In patients with left-scar-related VT, the maximal depth of CMR channels predicts VT recurrence after endocardial ablation. The maximal CMR channel depth could represent a parameter to guide an endocardial-only approach avoiding unnecessary epicardial access, with a cutoff of 7 mm that should be confirmed with larger studies.