Myocarditis, Infectious

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

Diagnosis

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

Imaging

• Chest radiograph

  • Nonspecific

  • However, cardiomegaly ...