Image-Based Criteria to Identify the Presence of Epicardial arrhythmogenic Substrate in Patients with Transmural Myocardial Infarction

Background Patients with transmural myocardial infarction (MI) who undergo endocardial-only substrate ablation are at increased risk for ventricular tachycardia recurrence. Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) can be used to assess infarct transmurality (IT). However, the degree of IT associated with an epicardial arrhythmogenic substrate (AS) has not been determined. Objective The purpose of this study was to determine the degree of IT observed by LGE-CMR and multidetector computed tomography (MDCT) that predicts the presence of epicardial AS. Methods The study included 38 post-MI patients. Ten patients with a subendocardial infarction underwent endocardial-only mapping, and 28 with a classic transmural MI (C-TMI), defined as hyperenhancement ≥75% of myocardial wall thickness (WT), underwent endo–epicardial mapping. LGE-CMR/MDCT data were registered to high-density endocardial or epicardial maps to be analyzed for the presence of AS. Results Of the 28 post-MI patients with C-TMI, 18 had epicardial AS (64%) and 10 (36%) did not. An epicardial scar area ≥14 cm 2 on LGE-CMR identified patients with epicardial AS (sensitivity 1, specificity 1). Mean WT in the epicardial scar area in these patients was lower than in patients without epicardial AS (3.14 ± 1.16 mm vs 5.54 ± 1.78 mm; P = .008). A mean WT cutoff value ≤3.59 mm identified patients with epicardial AS (sensitivity 0.91, specificity 0.93). Conclusion An epicardial scar area ≥14 cm 2 on LGE-CMR and mean CT-WT ≤3.59 mm predict epicardial AS in post-MI patients.