Isolated Critical Epicardial Arrhythmogenic Substrate Abnormalities in Patients with Arrhythmogenic Right Ventricular Cardiomyopathy and Ventricular Tachycardia.

BACKGROUND: Ventricular tachycardia (VT) substrate abnormalities in arrhythmogenic right ventricular cardiomyopathy (ARVC) typically involves both the RV endocardium (ENDO) and epicardium (EPI).

OBJECTIVE: To examine the prevalence, electrophysiological features, and outcomes of catheter ablation of VT in patients with isolated epicardial substrate (IES) abnormalities.

METHODS: We studied 71 consecutive patients with VT who met Task Force Criteria for ARVC and underwent detailed ENDO and EPI mapping. Patients with critical isolated epicardial substrate demonstrated 1) confluent EPI bipolar abnormal electrograms (EGMs) and 2) no or minor, (<5.0cm2 ) RV ENDO low bipolar voltage. Induced VTs were localized using activation, entrainment, and/or pace-mapping.

RESULTS: Twelve patients (17%) had isolated epicardial substrate. All patients had extensive EPI Bi-LVA (74±40cm2 ) and EGM abnormalities identified. Uni-ENDO LVA (<5.5mV) was seen in 11/12 (92%) patients (41±25cm2 ) and corresponded to EPI RV bipolar abnormalities. A median of 2 VTs (range 1-7, cycle length 288±68ms) were induced and localized to the epicardium. EPI ablation resulted in non-inducibility of all targeted VTs. Pre-ablation cardiac magnetic resonance (CMR) imaging was performed in 10/12 patients with RV dyskinesis and/or late gadolinium enhancement in only 4/10 patients. During follow-up of 56±46 months, 9/12 (75%) patients remained VT free.

CONCLUSIONS: In patients with ARVC and VT, substrate abnormalities can uncommonly be isolated to the RV epicardium. Detection of critical isolated epicardial substrate may be limited with CMR imaging, but suggested by ENDO unipolar EGM abnormalities. Epicardial ablation eliminates VT in these patients and typically results in long-term VT free survival.