Tissue heterogeneity detected on computed tomography (CT) may allow to distinguish between arrhythmogenic right ventricular cardiomyopathy (ARVC) and exercise-induced arrhythmogenic remodeling (EIAR), according to a study published in the American Journal of the College of Cardiology: Electrophysiology.

Patients with ARVC (n=17), EIAR (n=9), and control individuals (n=17) were recruited between 2006 and 2015 and assessed using detailed combined endocardial-epicardial electroanatomic mapping (EAM) during sinus rhythm and ventricular tachycardia (VT) ablation. ARVC was diagnosed using the 2010 revised Task Force Criteria, and EIAR, on the basis of VT after exclusion of ARVC and sarcoidosis. Control participants had no history of ventricular arrhythmia, abnormal electrocardiography results, or structural disease.

Normal points were defined as no scar, normal bipolar and unipolar voltage for endocardial mapping points. Late potential-positive (LP+) sites had a scar and late potentials (ie, abnormal bipolar and/or unipolar voltage with LP); LP-negative (LP-) sites had a scar and no LP. Groups were comparable at baseline in terms of age, sex, body mass index, and rates of diabetes mellitus or hypertension.

Of the total 5215 ARVC mapping points, 11% were LP+. LP+ sites had higher CT heterogeneity when compared with normal sites (median, 31 HU/mm; interquartile range [IQR], 23-46 vs median, 16 HU/mm; IQR, 13-21, respectively; P <.001). The optimal CT heterogeneity cut-off for differentiating LP+ from normal sites was 25 HU/mm (area under the curve [AUC], 0.80; sensitivity, 72%, specificity, 78%).


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Among patients with ARVC, the intramyocardial fat was 12% (IQR, 3-29%). Fat percentage was higher in LP+ vs normal sites. The optimal cut-off for intramyocardial fat to detect LP+ was 6% (AUC, 0.58; sensitivity, 80%; specificity, 37%).

A total of 2562 points were mapped in patients with EIAR. Only 3% of points were LP+, all located in the epicardium. CT heterogeneity did not differ across mapping point categories. In this group, median intramyocardial fat was 8% (IQR, 0%-26%) which was higher at LP+ vs normal points (P <.001).

Patients with EIAR vs ARVC had lower CT heterogeneity (P <.001). The overall CT heterogeneity level that allowed for the most accurate differentiation between ARVC and EIAR was an AUC of 0.78 (sensitivity, 65%; specificity, 89%), and AUC of 0.97 for the distinction between ARVC and controls (sensitivity, 100%; specificity, 82%).

Study limitations include the small sample size and the fact that patients were undergoing CT for VT ablation.

“RV tissue heterogeneity, quantified by CT, has a high sensitivity and specificity for the detection of low-voltage areas harboring LP+ as a potential VT substrate in patients with ARVC. The overall tissue heterogeneity allows for highly accurate differentiation between patients with ARVC, those with EIAR, and control individuals,” concluded the study authors. “This novel parameter may be an important diagnostic tool to distinguish ARVC from EIAR and normal RV and to guide VT ablation in patients with ARVC.”

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Venlet J, Tao Q, de Graaf M A, et al. RV Tissue Heterogeneity on CT. A Novel Tool to Identify the VT Substrate in ARVC. [Published online May 12, 2020] JACC: Clin Electrophysiol. doi:10.1016/j.jacep.2020.04.029