Background:
Myocarditis is an inflammatory disease of the myocardium with highly variable clinical presentation, ranging from subclinical symptoms such as fatigue and palpitations to fulminant heart failure and sudden cardiac death. Cardiac magnetic resonance imaging (CMR) has become a key non-invasive diagnostic tool, capable of detecting myocardial edema and late gadolinium enhancement (LGE). However, a definitive diagnosis of myocarditis can only be established by endomyocardial biopsy, which remains the gold standard despite its limited use in clinical practice.
Presentation of Case:
A 33-year-old woman, a former competitive field hockey athlete, was referred to our hospital from a fertility clinic due to bradycardia and a positive point-of-care troponin test. She reported fatigue and palpitations. ECG showed T-wave inversions in leads V1–V4 and premature ventricular contractions (PVCs) with left bundle branch block morphology. Echocardiography was unremarkable. Initial MRI revealed subepicardial LGE in the inferolateral wall without edema. Due to ongoing troponin elevation, repeat MRI showed progressive LGE and new regional edema, consistent with active myocarditis. RV function was mildly reduced with dilation, lobulated wall morphology, and RV LGE. Findings were suggestive of arrhythmogenic right ventricular cardiomyopathy (ARVC), though post-inflammatory changes or sarcoidosis could not be excluded. High-sensitivity cardiac troponin I (hs-cTnI) levels subsequently rose to a peak level of 304,006.5 pg/ml. A myocardial biopsy of the right ventricle was non- diagnostic. However, a subsequent biopsy of the left ventricle showed evidence of severe acute lymphocytic myocarditis. PCR-testing of endomyocardial biopsy tissue was positive for human herpesvirus 6 (HHV-6). At this point immunosuppressive therapy with prednisolone in combination with ganciclovir was started to cover viral myocarditis. The combined treatment led to a marked and rapid decline in troponin levels, indicating resolution of active myocardial inflammation. Ganciclovir was discontinued after one week, and prednisolone was gradually tapered over the following weeks. The patient was discharged with a working diagnosis of myocarditis and was subsequently followed in our outpatient heart failure clinic. In light of cardiac MRI findings suggestive of arrhythmogenic right ventricular cardiomyopathy (ARVC), genetic testing was initiated and revealed a likely pathogenic variant in the PKP2 gene, which encodes plakophilin 2. Serial Holter ECG monitoring demonstrated a relatively high burden of premature ventricular complexes (PVCs) as well as episodes of non-sustained ventricular tachycardia (VT). An electrophysiology study confirmed the arrhythmogenic substrate through induction of sustained VT, and catheter ablation was performed. After a period of clinical stability, the patient experienced a symptomatic VT episode. Given the confirmed diagnosis of ARVC and the occurrence of sustained symptomatic arrhythmia, a subcutaneous implantable cardioverter-defibrillator (S-ICD) was placed for secondary prevention. Since then, the patient has remained clinically stable, reporting only minimal symptoms.
Conclusion:
This case highlights the potential overlap between clinical presentations of myocarditis and ‘hot-phase’ ARVC, emphasizing the importance of multimodal diagnostic work-up and genetic testing in this scenario.
