Expansion
Inflammation of the myocardium, usually viral, often mimicking infarction
Expansion
Causes
- Viral, much the commonest: Coxsackie B, adenovirus, parvovirus B19, influenza, HIV, SARS-CoV-2
- Bacterial and other infection: diphtheria toxin, Lyme disease, Chagas disease (Trypanosoma cruzi), rheumatic fever
- Autoimmune: lupus, sarcoidosis, giant cell myocarditis
- Drugs and toxins: clozapine, anthracyclines, checkpoint inhibitors, cocaine, alcohol
- Hypersensitivity reactions
Presentation varies from asymptomatic to fulminant
- Chest pain mimicking infarction, often after a viral prodrome
- Heart failure, arrhythmia, sudden cardiac death in the young
- Raised troponin with unobstructed coronary arteries
Investigations: raised inflammatory markers and troponin, ECG changes that may mimic infarction or pericarditis, echocardiography, and cardiac MRI with late gadolinium enhancement in a subepicardial or mid-wall pattern, which distinguishes it from the subendocardial pattern of infarction. Endomyocardial biopsy is the reference standard but is rarely needed.
Management is supportive, with heart failure treatment, arrhythmia monitoring and avoidance of exercise for 3 to 6 months. Most recover, but a proportion progress to dilated cardiomyopathy.