• Clinical science

Myocarditis

Abstract

Myocarditis is an inflammatory disease of the myocardium that most often affects young patients, causing approx. 10% of sudden deaths in young adults. The disease is commonly caused by viral infections (e.g., parvovirus B19, coxsackie virus) or acute rheumatic fever, but may also manifest in patients with systemic conditions such as systemic lupus erythematosus or vasculitic syndromes. Adult patients are commonly asymptomatic or present with nonspecific symptoms, including fever, fatigue, and weakness. Some patients also experience cardiac signs that vary in severity from chest pain and arrhythmias to heart failure or sudden cardiac death. Infants and children typically have a more severe presentation. Inflammation may also spread and lead to concurrent pericarditis. Myocarditis should be suspected in patients with a history of flulike symptoms and new evidence of ECG abnormalities, such as sinus tachycardia or concave ST-segment elevations. Further diagnostic tests may show elevated cardiac enzymes and cardiac enlargement in chest x-rays. If diagnosis is uncertain, an additional myocardial biopsy may also be indicated. Initial management of myocarditis involves supportive measures and treatment of any underlying diseases (e.g., antibiotic therapy). Cardiac symptoms usually require additional medication, including amiodarone for arrhythmias or beta blockers for congestive heart failure. Whereas most adults with viral myocarditis make a full recovery, there is a small risk of the condition progressing to dilated cardiomyopathy. The prognosis is especially poor for infants and small children.

Epidemiology

  • The exact incidence is unknown.
    • ∼ 1–5% of viral infections are estimated to have cardiac involvement.
    • Often occurs in young patients (average age: ∼ 40 years)
    • In ∼ 10% of sudden deaths in young adults, myocarditis is diagnosed in the post-mortem examination.

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Infectious

Noninfectious

References:[3][1]

Clinical features

The clinical manifestation of myocarditis is very heterogenous and nonspecific, ranging from asymptomatic courses to fulminant cardiac decompensation!
References:[4]#544][5]

Diagnostics

Patients suspected of myocarditis should have an ECG and laboratory tests conducted to support the diagnosis. Ultimately, if the diagnosis is unclear, a biopsy may be indicated to help determine treatment.

ECG/24-hour Holter monitoring

Although ECG abnormalities due to myocardial inflammation are very nonspecific and may only manifest temporarily, myocarditis should be suspected if the following findings are observed:

Laboratory findings

Imaging

  • Chest x-ray and CT: cardiac enlargement, pulmonary congestion, pleural effusions
  • Echocardiography
    • Findings often unremarkable
    • Ventricles: dilation, diffuse hypokinesia, reduced ejection fraction, impaired contractility, regional wall motion abnormalities
    • Pericardial effusion: localized or circumferential fluid surrounding the ventricles
    • Exclusion of other possible etiologies of heart failure (e.g., heart defects)
  • Cardiac MRI
    • Diagnosis and follow-ups
    • Evidence of inflammatory edema
    • Detection of changes in ventricular size and shape, wall motion abnormalities

Myocardial biopsy

  • Via cardiac catheterization of the left heart and MRI-supported biopsy
    • Indications
      • New onset heart failure, severe arrhythmias, resistance to treatment
      • Only performed if previous diagnostics are inconclusive and a definitive diagnosis of myocarditis might influence treatment
    • Procedure (see “coronary angiography”)
      • The biopsy site is identified prior to catheterization via cardiac MRI.
      • Not a routine procedure due to the risk of severe complications (perforation, arrhythmias)
    • Results

References:[1][4][2]

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

References:[1][6][4]

Complications

References:[4][1]

We list the most important complications. The selection is not exhaustive.

Prognosis

References:[1][7][4]