Scarring/arrhythmogenic cardiomyopathy

: The designation of 'arrhythmogenic cardiomyopathy' reflects the evolving concept of a heart muscle disease affecting not only the right ventricle (ARVC) but also the left ventricle (LV), with phenotypic variants characterized by a biventricular (BIV) or predominant LV involvement (ALVC). Herein, we use the term 'scarring/arrhythmogenic cardiomyopathy (S/ACM)' to emphasize that the disease phenotype is distinctively characterized by loss of ventricular myocardium due to myocyte death with subsequent fibrous or fibro-fatty scar tissue replacement. The myocardial scarring predisposes to potentially lethal ventricular arrhythmias and underlies the impairment of systolic ventricular function. S/ACM is an 'umbrella term' which includes a variety of conditions, either genetic or acquired (mostly post-inflammatory), sharing the typical 'scarring' phenotypic features of the disease. Differential diagnoses include 'non-scarring' heart diseases leading to either RV dilatation from left-to-right shunt or LV dilatation/dysfunction from a dilated cardiomyopathy. The development of 2020 upgraded criteria ('Padua criteria') for diagnosis of S/ACM reflected the evolving clinical experience with the expanding spectrum of S/ACM phenotypes and the advances in cardiac magnetic resonance (CMR) imaging. The Padua criteria aimed to improve the diagnosis of S/ACM by incorporation of CMR myocardial tissue characterization findings. Risk stratification of S/ACM patients is mostly based on arrhythmic burden and ventricular dysfunction severity, although other ECG or imaging parameters may have a role. Medical therapy is crucial for treatment of ventricular arrhythmias and heart failure. Implantable cardioverter defibrillator (ICD) is the only proven life-saving treatment, despite its significant morbidity because of device-related complications and inappropriate shocks. Selection of patients who can benefit the most from ICD therapy is one of the most challenging issues in clinical practice.