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For further information, see CMDT Part 10-42: Infectious Myocarditis

Key Features

Essentials of Diagnosis

  • Often follows an upper respiratory infection

  • May present with chest pain (pleuritic or nonspecific) or signs of heart failure

  • Echocardiogram documents cardiomegaly and contractile dysfunction

  • Myocardial biopsy, though not sensitive, may reveal a characteristic inflammatory pattern; MRI has a role in diagnosis

General Considerations

  • Cardiac dysfunction due to primary myocarditis is presumedly caused by either an acute viral infection or a postviral immune response

  • Causes include

    • RNA viruses

      • Picornaviruses (coxsackie A and B, echovirus, poliovirus, hepatitis virus)

      • Orthomyxovirus (influenza)

      • Paramyxoviruses (respiratory syncytial virus, mumps)

      • Togaviruses (rubella)

      • Flaviviruses (dengue fever, yellow fever)

      • SARS-CoV-2 (COVID-19)

    • DNA viruses

      • Adenovirus (A1, 2, 3, and 5)

      • Erythrovirus (Bi9V and 2)

      • Herpesviruses (human herpes virus 6 A and B, cytomegalovirus, Epstein-Barr virus, varicella-zoster)

      • Retrovirus (HIV)

    • Bacteria

      • Chlamydia (Chlamydophila pneumoniae, C psittaci)

      • Haemophilus influenzae

      • Legionella

      • Pneumophilia

      • Brucella

      • Clostridium

      • Francisella tularensis

      • Neisseria meningitis

      • Mycobacterium (tuberculosis)

      • Salmonella

      • Staphylococcus

      • Streptococcus A, Streptococcus pneumoniae

      • Tularemia

      • Tetanus

      • Syphilis

      • Vibrio cholera

    • Spirocheta

      • Borrelia recurrentis

      • Leptospira

      • Treponema pallidum

    • Rickettsia

      • Coxiella burnetti

      • R rickettsii, R prowazekii

    • Fungi

      • Actinomyces

      • Aspergillus

      • Candida

      • Cryptococcus

      • Histoplasma

      • Nocardia

    • Protozoa

      • Entamoeba histolytica

      • Plasmodium falciparum

      • Trypanosoma cruzi, T burcei, T gondii

      • Leishmania

    • Helminthic

      • Ascaris

      • Echinococcus granulosus

      • Schistosoma

      • Trichenella spiralis

      • Wuchereria bancrofti

Clinical Findings

  • Patients may present several days to a few weeks after the onset of an acute febrile illness or a respiratory infection or they may present with heart failure without antecedent symptoms

  • Onset of heart failure may be gradual or may be abrupt and fulminant

  • In acute fulminant myocarditis,

    • Low output and shock may be present with severely depressed LV systolic function

    • The LV chamber size is typically not very enlarged

  • A pericardial friction rub may be present

  • In the European Study of Epidemiology and Treatment of Inflammatory Heart Disease,

    • 72% of participants had dyspnea

    • 32% had chest pain

    • 18% had arrhythmias

  • Pulmonary and systemic emboli may occur

  • Pleural-pericardial chest pain is common

  • Examination reveals tachycardia, a gallop rhythm, and other evidence of heart failure or conduction defects

  • At times, the presentation may mimic an acute myocardial infarction with ST changes, positive cardiac markers, and regional wall motion abnormalities despite normal coronaries

  • Microaneurysms may also occur and may be associated with serious ventricular arrhythmias

  • Approximately 10% of all dilated cardiomyopathy patients have viral myocarditis as the cause


Laboratory Findings

  • No specific laboratory finding

  • However, white blood cell count is usually elevated

  • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are usually increased

  • Troponin I or T levels are elevated in about one-third of patients, but CK-MB is elevated in only 10%

  • Other biomarkers, such as B-type natriuretic peptide (BNP and proBNP), are usually elevated


  • Chest radiograph

    • Nonspecific

    • However, cardiomegaly ...

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