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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; initial heart size is generally normal with thickened walls

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

  • COVID-19 myocarditis has been reported between 3% and 58% of people based on underlying myocardial risk and imaging

General Considerations

  • Cardiac dysfunction due to primary myocarditis is presumably caused by either an acute viral infection or a post viral 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)

    • 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

  • SARS-CoV-2

    • Myopericarditis has been a concern during the COVID-19 pandemic; much remains unknown

    • Speculation is that the Spike protein binds to the angiotensin-converting enzyme 2 (ACE-2) membrane receptor on cardiomyocytes creating direct cellular injury and T-lymphocyte-mediated cytotoxicity augmented by a cytokine storm

    • Myocarditis following natural SARS-CoV-2 infection and post vaccination, according to the CDC

      • 13.3 myocarditis cases per 100,000 recipients of the Moderna vaccine

      • 2.7 cases per 100,000 recipients of the Pfizer-BioNTech vaccine

      • The variation in the myocarditis rates between the two vaccines is not understood and is the focus on ongoing research

      • 150 cases per 100,000 post natural SARS-CoV-2 infection

    • In a German study of 100 patients who had recovered from COVID-19, cardiac MRI revealed some degree of abnormality in 78 patients, with inflammation noted in 60, independent of severity of the illness

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

  • 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 ...

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