Abstract
A retrospective study was conducted on pathologically diagnosed arrhythmogenic cardiomyopathy (ACM) from consecutive cases over the past 34 years (n = 1109). The anatomo-pathological analyses were performed on 23 hearts diagnosed as ACM (2.07%) from a series of 1109 suspected cases, while histopathological data of cardiac conduction system (CCS) were available for 15 out of 23 cases. The CCS was removed in two blocks, containing the following structures: Sino-atrial node (SAN), atrio-ventricular junction (AVJ) including the atrio-ventricular node (AVN), the His bundle (HB), the bifurcation (BIF), the left bundle branch (LBB) and the right bundle branch (RBB). The ACM cases consisted of 20 (86.96%) sudden unexpected cardiac death (SUCD) and 3 (13.04%) native explanted hearts; 16 (69.56%) were males and 7 (30.44%) were females, ranging in age from 5 to 65 (mean age ± SD, 36.13 ± 16.06) years. The following anomalies of the CCS, displayed as percentages of the 15 ACM SUCD cases in which the CCS has been fully analyzed, have been detected: Hypoplasia of SAN (80%) and/or AVJ (86.67%) due to fatty-fibrous involvement, AVJ dispersion and/or septation (46.67%), central fibrous body (CFB) hypoplasia (33.33%), fibromuscular dysplasia of SAN (20%) and/or AVN (26.67%) arteries, hemorrhage and infarct-like lesions of CCS (13.33%), islands of conduction tissue in CFB (13.33%), Mahaim fibers (13.33%), LBB block by fibrosis (13.33%), AVN tongue (13.33%), HB duplicity (6.67%%), CFB cartilaginous meta-hyperplasia (6.67%), and right sided HB (6.67%). Arrhythmias are the hallmark of ACM, not only from the fatty-fibrous disruption of the ventricular myocardium that accounts for reentrant ventricular tachycardia, but also from the fatty-fibrous involvement of CCS itself. Future research should focus on application of these knowledge on CCS anomalies to be added to diagnostic criteria or at least to be useful to detect the patients with higher sudden death risks.
Highlights
Arrhythmogenic cardiomyopathy (ACM), formerly known as arrhythmogenic right ventricular cardiomyopathy (ARVC), is an inheritable type of cardiomyopathy not secondary to ischemic, hypertensive, or valvular heart disease characterized by ventricular fibro-fatty myocardial replacement and prominent scar-related arrhythmias
Of a series of 1109 cases submitted to the Lino Rossi Research Center of the Università degli Studi di Milano, Milan, Italy, for in depth- specialized anatomo-pathological investigations, collected from January 1987 to 23 April 2021 (2.07%) submitted hearts were diagnosed anatomo-pathologically as arrhythmogenic cardiomyopathy (ACM)
In this sudden unexpected cardiac death (SUCD) group, including an age range from 22 gestational weeks to 90 years, we identified 20 (2.43%) ACM cases
Summary
Arrhythmogenic cardiomyopathy (ACM), formerly known as arrhythmogenic right ventricular cardiomyopathy (ARVC), is an inheritable type of cardiomyopathy not secondary to ischemic, hypertensive, or valvular heart disease characterized by ventricular fibro-fatty myocardial replacement and prominent scar-related arrhythmias. ACM is characterized by progressive loss of myocardium replaced by fibro-fatty tissue, especially in the right ventricle. ACM is a hereditary Mendelian desmosome disease, typically dominant and rarely recessive, with mutations of genes encoding intercellular proteins. Most of the pathogenic variants in ACM have been identified in genes encoding the intercalated disk (ID) proteins junction plakoglobin (JUP), desmoplakin (DSP), plakophilin-2 (PKP2), desmoglein-2 (DSG2), desmocollin-2 (DSC2), α-T-catenin (CTNNA3), and N-cadherin (CDH2). Of 26 reported ARVC genes, six genes, PKP2, DSP, DSG2, DSC2, JUP, and TMEM43, have strong evidence for ARVC causation. The remaining 18 genes, such as RYR2, had limited or no evidence for ARVC
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