RV Tissue Heterogeneity on CT: A Novel Tool to Identify the VT Substrate in ARVC.

ABSTRACT

OBJECTIVES: This study sought to evaluate whether right ventricular (RV) tissue heterogeneity on computed tomography (CT) 1) is associated with conduction delay in arrhythmogenic right ventricular cardiomyopathy (ARVC); and 2) distinguishes patients with ARVC from those with exercise-induced arrhythmogenic remodeling (EIAR) and control individuals. BACKGROUND: ARVC is characterized by fibrofatty replacement, related to conduction delay and ventricular tachycardias. Distinguishing ARVC from acquired, EIAR is challenging. METHODS: Patients with ARVC or EIAR and combined endocardial-epicardial electroanatomic voltage mapping for VT ablation with CT integration were enrolled. Patients without structural heart disease served as control individuals. Tissue heterogeneity on CT (CT heterogeneity) was automatically quantified within the 2-mm subepicardium of the entire RV free wall at normal sites and low voltage sites harboring late potentials (LP+) in ARVC/EIAR. RESULTS: Seventeen patients with ARVC (15 males; age 50 ± 17 years), 9 patients with EIAR (7 males; age 45 ± 14 years) and 17 control individuals (14 males; age 50 ± 15 years) were enrolled. Of 5,215 ARVC mapping points, 560 (11%) showed LP+. CT heterogeneity was higher at sites with LP+ compared to normal sites (median 31 HU/mm; IQR 23 to 46 HU/mm vs. median 16 HU/mm; IQR 13 to 21 HU/mm; p < 0.001). The optimal CT heterogeneity cutoff for detection of LP+ was 25 HU/mm (area under the curve [AUC] 0.80; sensitivity 72%; specificity 78%). Overall CT heterogeneity allowed highly accurate differentiation between patients with ARVC and control individuals (AUC 0.97; sensitivity 100%; specificity 82%) and between ARVC and EIAR (AUC 0.78; sensitivity 65%; specificity 89%). CONCLUSIONS: In patients with ARVC, tissue heterogeneity on CT can be used to identify LP+ as a surrogate for ventricular tachycardia substrate. The overall tissue heterogeneity on CT allows the distinguishing of patients with ARVC from those with EIAR and control individuals.