Background This study assessed the prevalence of left ventricular ( LV ) involvement and characterized the clinical, electrocardiographic, and imaging features of LV phenotype in patients with arrhythmogenic right ventricular cardiomyopathy ( ARVC ). Differential diagnosis between ARVC ‐ LV phenotype and dilated cardiomyopathy ( DCM ) was evaluated. Methods and Results The study population included 87 ARVC patients (median age 34 years) and 153 DCM patients (median age 51 years). All underwent cardiac magnetic resonance with quantitative tissue characterization. Fifty‐eight ARVC patients (67%) had LV involvement, with both LV systolic dysfunction and LV late gadolinium enhancement ( LGE ) in 41/58 (71%) and LV ‐ LGE in isolation in 17 (29%). Compared with DCM , the ARVC ‐ LV phenotype was statistically significantly more often characterized by low QRS voltages in limb leads, T‐wave inversion in the inferolateral leads and major ventricular arrhythmias. LV ‐ LGE was found in all ARVC patients with LV systolic dysfunction and in 69/153 (45%) of DCM patients. Patients with ARVC and LV systolic dysfunction had a greater amount of LV ‐ LGE (25% versus 13% of LV mass; P <0.01), mostly localized in the subepicardial LV wall layers. An LV ‐ LGE ≥20% had a 100% specificity for diagnosis of ARVC ‐ LV phenotype. An inverse correlation between LV ejection fraction and LV ‐ LGE extent was found in the ARVC ‐ LV phenotype ( r =−0.63; P <0.01), but not in DCM ( r =−0.01; P =0.94). Conclusions LV involvement in ARVC is common and characterized by clinical and cardiac magnetic resonance features which differ from those seen in DCM . The most distinctive feature of ARVC ‐ LV phenotype is the large amount of LV ‐ LGE /fibrosis, which impacts directly and negatively on the LV systolic function.

Criteria for diagnosis of arrhythmogenic cardiomyopathy (ACM) were first proposed in 1994 and revised in 2010 by a Task Force. Although the Task Force criteria demonstrated a good accuracy for diagnosis of the original right ventricular phenotype (arrhythmogenic right ventricular cardiomyopathy), they lacked sensitivity for identification of the expanding phenotypic spectrum of ACM, which includes left‐sided variants and did not incorporate late‐gadolinium enhancement findings by cardiac magnetic resonance. The 2020 International criteria (“Padua criteria”) have been developed by International experts with the aim to improve the diagnosis of ACM by providing new criteria for the diagnosis of left ventricular phenotypic features. The key upgrade was the incorporation of tissue characterization findings by cardiac magnetic resonance for noninvasive detection of late‐gadolinium enhancement/myocardial fibrosis that are determinants for characterization of arrhythmogenic biventricular and left ventricular cardiomyopathy. The 2020 International criteria are heavily dependent on cardiac magnetic resonance, which has become mandatory to characterize the ACM phenotype and to exclude other diagnoses. New criteria regarding left ventricular depolarization and repolarization ECG abnormalities and ventricular arrhythmias of left ventricular origin were also provided. This article reviews the evolving approach to diagnosis of ACM, going back to the 1994 and 2010 International Task Force criteria and then grapple with the modern 2020 International criteria.

Aims The aim of this study is to evaluate the clinical features of patients affected by arrhythmogenic cardiomyopathy (AC), presenting with chest pain and myocardial enzyme release in the setting of normal coronary arteries (‘hot phase’). Methods and results We collected detailed anamnestic, clinical, instrumental, genetic, and histopathological findings as well as follow-up data in a series of AC patients who experienced a hot phase. A total of 23 subjects (12 males, mean age at the first episode 27 ± 16 years) were identified among 560 AC probands and family members (5%). At first episode, 10 patients (43%) already fulfilled AC diagnostic criteria. Twelve-lead electrocardiogram recorded during symptoms showed ST-segment elevation in 11 patients (48%). Endomyocardial biopsy was performed in 11 patients, 8 of them during the acute phase showing histologic evidence of virus-negative myocarditis in 88%. Cardiac magnetic resonance was performed in 21 patients, 12 of them during the acute phase; oedema and/or hyperaemia were detected in 7 (58%) and late gadolinium enhancement in 11 (92%). At the end of follow-up (mean 17 years, range 1–32), 12 additional patients achieved an AC diagnosis. Genetic testing was positive in 77% of cases and pathogenic mutations in desmoplakin gene were the most frequent. No patient complained of sustained ventricular arrhythmias or died suddenly during the ‘hot phase’. Conclusion ‘Hot phase’ represents an uncommon clinical presentation of AC, which often occurs in paediatric patients and carriers of desmoplakin gene mutations. Tissue characterization, family history, and genetic test represent fundamental diagnostic tools for differential diagnosis.

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