Myocarditis — the diagnosis and the mimic of the infarction

The differential of the chest pain and the raised troponin: the acute coronary syndrome (the commonest concern), the myocarditis, the pericarditis and the myopericarditis, the pulmonary embolism, the tako-tsubo cardiomyopathy, the sepsis with the myocardial injury, and the renal failure. The viral prodrome, the young age, and the diffuse (or the non-territorial) ECG changes favour the myocarditis.^[3]

The diagnostic approach:

• The ECG (the non-specific changes, may mimic the ischaemia).
• The troponin (the raised, the myocardial injury).
• The echocardiography (the reduced ejection fraction, the regional wall motion, the wall thickening).
• The cardiac MRI with the Lake Louise criteria (the non-invasive standard — the late gadolinium enhancement in the mid-wall or the epicardial, non-ischaemic pattern, the T1 and the T2 mapping for the oedema).
• The coronary angiography in the selected (to exclude the ACS, especially if the risk factors).
• The endomyocardial biopsy (the gold standard, reserved for the fulminant or the uncertain).^[3]

The distinction of the myocarditis from the ACS:

• The myocarditis: the viral prodrome, the young, the diffuse ECG, the mid-wall non-ischaemic late enhancement on the MRI, the clean coronary arteries.
• The ACS: the risk factors, the territorial ST elevation or the depression, the subendocardial late enhancement (or the occlusion) on the imaging, the obstructive coronary disease on the angiography.^[3]

The management of the myocarditis: the supportive, the treat-the-cause, the avoidance of the competitive sport for the 3 to 6 months, the monitoring for the heart failure and the arrhythmia, and the specific treatment for the giant-cell, the immune-checkpoint-inhibitor, and the eosinophilic myocarditis.^[3] Intravenous immunoglobulin for presumed viral myocarditis has no proven survival benefit — the Cochrane evidence is of very low certainty and insufficient to support routine use.^[4]