Limited impact of endocardial radiofrequency ablation on epicardial substrate in post-infarction ventricular tachycardia

Catheter ablation is key therapy for post-myocardial infarction (post-MI) ventricular tachycardia (VT). However, outcomes remain suboptimal when an endocardial-only approach is used because epicardial or intramural substrate frequently contributes to arrhythmogenesis. This study aimed to quantify the prevalence and extent of epicardial substrate in post-MI VT and to assess the direct impact of endocardial radiofrequency (RF) ablation on epicardial electrograms. Thirty-seven consecutive patients with ischemic cardiomyopathy and sustained VT (mean age 67 ± 8 years; left ventricular ejection fraction 30 ± 10%) underwent combined endocardial and epicardial substrate ablation. Epicardial access was obtained using carbon dioxide (CO2) insufflation-assisted subxiphoid puncture. Electroanatomical mapping (CARTO 3) and contact force-sensing RF ablation guided by Ablation Index were used. The impact of endocardial RF on opposite-surface epicardial electrograms was quantified. Epicardial low-voltage area (< 0.5 mV) was present in 35 patients (95%) and epicardial late potentials in 32 (86%). Endocardial RF delivery time was 20 ± 9.8 min. No measurable change in opposite epicardial signals was observed in 21 patients; partial attenuation occurred in 11, and complete elimination in none. Over 24 ± 15 months of follow-up, VT recurred in 3 patients (10%); one cardiac and one non-cardiac death occurred. Epicardial substrate is highly prevalent in post-MI VT and is rarely eliminated by endocardial RF alone. Combined endo-epicardial mapping and ablation using CO2-assisted access may facilitate more comprehensive substrate modification in selected high-risk patients. Epicardial scar and late potentials were present in almost all post-MI VT patients. Standard endocardial radiofrequency lesions rarely affected opposite epicardial signals. CO2-assisted epicardial access facilitated combined substrate mapping and ablation with favorable mid-term arrhythmia outcomes.