Acute Myocarditis

Excerpt

Myocarditis refers to the inflammation of the myocardium, which can lead to tissue degeneration or necrosis. Myocarditis was previously referred to as inflammatory myocarditis, and the condition primarily affects individuals aged 40 or younger. Myocarditis is classified into 4 forms—acute, fulminant, chronic active, and chronic persistent.

Acute myocarditis accounts for approximately 65% of all myocarditis cases and is mainly caused by viral infections, although noninfectious etiologies may also contribute. Clinical presentation of acute myocarditis varies widely and may include febrile illness, mild chest pain, arrhythmias, heart failure, cardiogenic shock, or sudden death. The clinical diagnosis of the condition can be challenging due to the nonspecific nature of its symptoms, and treatment is generally supportive. The clinical course and prognosis of acute myocarditis are variable; while some patients recover fully within a few weeks, others experience an acute phase that progresses to chronic complications, such as dilated cardiomyopathy.

Diagnosing acute myocarditis remains challenging due to its variable clinical presentation and significant overlap with other cardiovascular conditions. Clinicians should maintain a high index of suspicion, particularly in younger patients presenting with symptoms suggestive of myocarditis but without conventional risk factors for coronary artery disease (CAD). A recent history of febrile illness, viral prodrome, or signs indicative of connective tissue disease can further raise suspicion for myocarditis. Myocardial involvement may be focal or diffuse, contributing to the heterogeneity of clinical manifestations. According to the 2024 American College of Cardiology (ACC) Expert Consensus Decision Pathway (ECDP), acute myocarditis is defined as a clinical episode that occurs within one month of symptom onset.