Evolution in the Diagnosis and Treatment of Myocarditis in Recent Years: State of the Art

Abstract

Acute myocarditis (AM) is an inflammatory cardiac condition resulting from infections, toxic exposures, or immune-mediated mechanisms, with clinical presentations ranging from mild symptoms to heart failure (HF) or cardiogenic shock. Although viral infections remain the predominant cause, both the absolute prevalence and the relative distribution of different etiologies may change over time and across regions depending on endemic diseases. Immune checkpoint inhibitor (ICI)-associated myocarditis has emerged as a newly recognized entity, with diagnostic rates increasing in parallel with growing awareness and the expanding population of cancer patients eligible for ICI therapy. Additionally, genetic predisposition—particularly mutations linked to arrhythmogenic cardiomyopathy—is also being increasingly acknowledged as a susceptibility factor. Recent advances have markedly improved the diagnostic approach to AM. The availability of high-sensitivity cardiac troponins and the widespread use of cardiac magnetic resonance imaging (CMRI) have enhanced early detection and tissue characterization. CMRI, especially following the updated Lake Louise Criteria (2018), which incorporate T1 and T2 mapping, enables accurate assessment of myocardial inflammation and fibrosis. Endomyocardial biopsy (EMB) remains essential in complicated cases, particularly to identify histologic subtypes that may benefit from immunosuppressive therapy. Early EMB (within 48 h) has been associated with better outcomes in fulminant presentations. The use of immunohistochemistry with leukocyte-specific markers has further increased the sensitivity of EMB. Therapeutic strategies now integrate etiology-specific approaches. Immunosuppressive therapy is indicated for distinct histological forms such as eosinophilic (EM) and giant cell myocarditis (GCM) or cases associated with systemic autoimmune disease. Conversely, in most patients with acute myocarditis complicated by acute HF or cardiogenic shock, no specific treatment is currently recommended beyond evidence-based management of acute HF and general supportive therapy.