Role of cardiac magnetic resonance in the differential diagnosis between arrhythmogenic cardiomyopathy with left ventricular involvement and previous infectious myocarditis

Coexistence of cardiac sarcoidosis and arrhythmogenic cardiomyopathy-associated genetic variants: a multicentre case-control study

BACKGROUND

Cardiac sarcoidosis (CS) is a chronic inflammatory disease characterised by non-caseating granulomas, while arrhythmogenic cardiomyopathy (ACM) is a genetic condition mainly affecting desmosomal proteins. The coexistence of CS and genetic variants associated with ACM is not well understood, creating challenges in diagnosis and management. This study aimed to describe the clinical, imaging and genetic features of patients with both conditions.

METHODS

This was a multicentre retrospective case-control study involving three groups of patients: those with biopsy-proven CS and pathogenic or likely pathogenic genetic variants linked to ACM (n=5); patients with genetic variants but no CS (n=5); and patients with CS without genetic variants (n=5). Clinical data, including symptoms, electrocardiographic findings and imaging results from echocardiography, cardiac magnetic resonance and positron-emission tomography, were analysed.

RESULTS

Patients with CS and genetic variants were more likely to exhibit atrioventricular block (100%), PR prolongation (204 ms vs 160 ms) and paroxysmal atrial fibrillation (80%) compared with those with genetic variants alone (0% for both). Imaging findings showed a higher prevalence of septal involvement in patients with both conditions (80%) than in those with genetic variants alone (20%). No significant differences were observed between patients with CS and genetic variants and those with CS without genetic variants. The genetic variants identified included variants in PKP2 (40%), DSG2 (20%), DSP (20%) and TTN (20%).

CONCLUSIONS

The coexistence of CS and ACM-associated genetic variants is associated with distinct clinical features, including PR prolongation, AVB1°, septal involvement and paroxysmal atrial fibrillation. These findings emphasise the need to evaluate for CS in individuals with ACM and associated genetic variants who present with conduction abnormalities or septal involvement, guiding tailored diagnostic and therapeutic strategies.

Role of genetics in inflammatory cardiomyopathy

Traditional cardiomyopathy paradigms segregate inflammatory etiologies from those caused by genetic variants. An identified or presumed trigger is implicated in acute myocarditis or chronic inflammatory cardiomyopathy but growing evidence suggests a significant proportion of patients have an underlying cardiomyopathy-associated genetic variant often even when a clear inflammatory trigger is identified. Recognizing a possible genetic contribution to inflammatory cardiomyopathy may have major downstream implications for both the patient and family. The presenting features of myocarditis (i.e. chest pain, arrhythmia, and/or heart failure) may provide insight into diagnostic considerations. One example is isolated cardiac sarcoidosis, a distinct inflammatory cardiomyopathy that carries diagnostic challenges and clinical overlap; genetic testing has increasingly reclassified cases of isolated cardiac sarcoidosis as genetic cardiomyopathy, notably altering management. On the other side, inflammatory presentations of genetic cardiomyopathies are likewise underappreciated and a growing area of investigation. Inflammation plays an important role in the pathogenesis of several familial cardiomyopathies, especially arrhythmogenic phenotypes. Given these clinical scenarios, and the implications on clinical decision making such as initiation of immunosuppression, sudden cardiac death prevention, and family screening, it is important to recognize when genetics may be playing a role.