Characterization of right ventricular low voltage areas in patients with arrhythmogenic right ventricular cardiomyopathy
Authors: Bialobroda J , Badenco N , Duthoit G , Waintraub X , Charpentier E , Kachenoura N , Redheuil A , Gandjbakhch E , Laredo M 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement in the myocardium progressing from the epicardium towards the endocardium and affecting primarily the right ventricle (RV). Little data is available on the distribution of RV electrical abnormalities at the era of epicardial and high-resolution mapping.

Purpose
To evaluate the extent and distribution of RV epicardial and endocardial low voltage areas and their relationship with ECG abnormalities in ARVC patients.

Methods
Patients with a definite ARVC diagnosis according to the 2020 Task Force Criteria, who underwent ventricular tachycardia ablation between 2016 and 2022 with a high-density RV 3-dimensional electroanatomic mapping, were included. A custom RV segmentation dividing the RV into 10 segments from endocardial maps was used: anterior and lateral right ventricular outflow tract (RVOT); basal and mid inferior wall; apex; septum; basal anterolateral, basal inferolateral, mid anterolateral and mid inferolateral RV free wall (Figure). A standard definition of electrical scar was used (bipolar voltage ≤0.5 mV), and scar areas were manually delineated. Percentage of scar was defined by the ratio between scar area and the total segment area. ECG abnormal findings, such as epsilon wave and T-wave inversion in precordial leads, were measured before ablation procedure.

Results
Twenty-nine consecutive definite ARVC patients were included, among whose 24 had epicardial mapping in addition to endocardial mapping. When considering all segments, the epicardial scar (median:70%, interquartile range [IQR] 37-97%) was larger (p&lt;0.0001) than the endocardial scar (9% [IQR] 0-32%).
The higher percentage of epicardial scar was found in the basal inferolateral (100% [IQR] 73-100%), basal anterolateral (94% [IQR] 67-100%), RV free wall and lateral RVOT (89% [IQR] 48-100%) segments (Table). Transmural scar was observed mostly in basal inferolateral RV free wall (10 patients, 41%) and basal inferior wall (8 patients, 33%). Patients with major depolarization criteria had a higher percentage of epicardial and endocardial scar as compared to those with no or minor depolarization criteria (respectively 93% [IQR] 59-100% versus 62% [IQR] 28-89%, p&lt;0.0001 and 17% [IQR] 0-42% versus 4% [IQR] 0-23%, p=0.001). There was no significant difference of the percentage of epicardial or endocardial scar in patients with and without major repolarization criteria (respectively 90% [IQR] 49-98% versus 84% [IQR] 43-100%, p=0.91 and 14% [IQR] 11-35% versus 16% [IQR] 0-41%, p=0.73).

Conclusion
In ARVC, the electrical abnormalities predominate in the basal epicardium. Patients with major depolarization criteria had a higher extent of epicardial and endocardial scar, but there was an association between scar extent and repolarization abnormalities.