Myocarditis

Myocarditis describes a heterogeneous group of disorders characterised by myocardial inflammation in the absence of predominant acute or chronic ischaemia.

Can affect all age groups with an apparent slightly higher incidence in males than females and equal incidence in black people and white people.

May present as fulminant, acute, or chronic myocarditis.

Treatment is usually supportive care and conventional heart failure therapy. More severe presentations may need aggressive pharmacological treatment with escalation to mechanical circulatory support. Occasionally, some cases do not respond to conventional therapy and progress to heart transplantation or death.

Prognosis is variable but is related to presentation and underlying aetiology. Most cases of viral myocarditis are asymptomatic and spontaneously resolve. Patients who present with mild to moderate heart failure tend to improve or recover but may progress to chronic severe heart failure. Surprisingly, patients who present with fulminant, acutely decompensated heart failure almost universally recover back to baseline function, if death is prevented through management in the acute phase.

Myocarditis is clinically and pathologically defined as inflammation of the myocardium in the absence of the predominant acute or chronic ischaemia characteristic of coronary artery disease. It is a clinical syndrome of non-ischaemic myocardial inflammation resulting from a heterogeneous group of infectious, immune, and non-immune diseases. Histopathologically, it is characterised by an inflammatory cellular infiltrate with or without evidence of myocyte injury.[1]Tschöpe C, Ammirati E, Bozkurt B, et al. Myocarditis and inflammatory cardiomyopathy: current evidence and future directions. Nat Rev Cardiol. 2021 Mar;18(3):169-93. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7548534 http://www.ncbi.nlm.nih.gov/pubmed/33046850?tool=bestpractice.com ​​[Figure caption and citation for the preceding image starts]: Histological findings in a patient with giant cell myocarditis. A: severe myocardial necrosis and fibrotic replacement of the cardiomyocytes with granulation tissue and fibrosis is present in a section from the anterolateral left ventricular wall; B: a sharp demarcating border between vital and necrotic myocardium is seen, confirmed by additional immunohistochemical staining for myoglobin; C: at the inflammatory border, cells consisting of prominent multi-nucleated giant cells, macrophages, lymphocytes, and eosinophilic granulocytes are seen in close proximity to vital myocardium; D: immunohistochemical staining for complement 4d is positive in all vessels, suggestive of complement cascade activationFrom: Rasmussen TB, Dalager S, Andersen NH, et al. BMJ Case Reports 2009; doi:10.1136/bcr.09.2008.0997 [Citation ends].