Suspected Arrhythmogenic Left Ventricular Cardiomyopathy: The Great Imitator Unveiled by Cardiac MRI: A Case Report

Abstract

Background: Arrhythmogenic left ventricular cardiomyopathy (ALVC) is a rare and often underdiagnosed subtype of arrhythmogenic cardiomyopathy (ACM), characterized by predominant left ventricular involvement and a high risk of arrhythmias. In contrast to the classic right dominant form, ALVC presents significant diagnostic challenges due to its phenotypic overlap with other cardiomyopathies and the limited availability of genetic testing. Case Presentation: We report the case of a 55-year-old man with a history of hypertension and active smoking, who presented with progressive dyspnea, syncope, and palpitations. Initial evaluation revealed atrial fibrillation with rapid ventricular response, elevated troponin and BNP levels, and signs of congestive heart failure. Transthoracic echocardiography demonstrated left ventricular hypertrophic cardiomyopathy with severely reduced left ventricular ejection fraction (LVEF 34%) and global longitudinal strain (GLS) of -11.3%. Cardiac magnetic resonance (CMR) imaging showed moderate left ventricular dilation with significant septal hypertrophy, systolic dysfunction (LVEF 33%), and characteristic subepicardial and mid-myocardial late gadolinium enhancement (LGE) involving more than 30% of the myocardial mass, while the right ventricle remained unaffected.  Comprehensive workup excluded cardiac sarcoidosis through negative angiotensin-converting enzyme levels, phosphocalcic assessment, salivary gland biopsy, and thoracic CT. Twenty-four-hour Holter monitoring revealed ventricular hyperexcitability with non-sustained ventricular tachycardia episodes and a 22% premature ventricular contraction burden. Management and Outcome: Given the high risk of sudden cardiac death (SCD), the patient received an implantable cardioverter-defibrillator (ICD) and antiarrhythmic therapy with amiodarone, resulting in a significant reduction of arrhythmia burden, with premature ventricular contractions burden decreasing to 1.3%. Conclusion: This case highlights the diagnostic complexity of ALVC and emphasizes the importance of multimodal imaging and the systematic exclusion of differential diagnoses. In settings with limited access to genetic testing, comprehensive clinical evaluation remains crucial for early recognition and appropriate risk stratification of this potentially life-threatening condition.