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; 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 ...