Myocarditis

Basics

Description

  • An inflammatory disease of the myocardium with myocardial injury with or without necrosis leading to variable cardiac dysfunction, arrhythmias, or heart failure
  • Infectious agents (eg, viruses, bacteria) or noninfectious triggers (autoimmune diseases, toxins) invade cardiomyocytes, disrupting cellular integrity and function activating innate and adaptive immune responses
  • Inflammatory infiltrates (T-cells, macrophages) cause cardiomyocyte damage, leading to myocardial edema, contractile dysfunction, arrhythmias, and, in severe cases, acute heart failure
  • Persistent inflammation results in extracellular matrix remodeling, fibrosis, and ventricular dilation, potentially leading to dilated cardiomyopathy, progressive heart failure, or sudden cardiac death
  • True incidence is unknown because many cases are asymptomatic
  • Autopsy studies have demonstrated evidence of myocarditis in 1–7% of cases and >50% in HIV patients
  • Male > female (1.5:1)
  • Average age of patients with myocarditis is 33 yr for women and 46 yr for men
  • Major cause of unexpected sudden death (15–20% of cases) <40 yr old

Etiology

  • Viral:
    • COVID-19:
      • Myocarditis incidence increased 15 times from baseline after COVID-19
      • MIS-C (immune dysregulation precipitated by COVID-19 infection)
    • Parvovirus B19:
      • One of the most common viral causes
    • Most viruses can cause myocarditis
  • Bacteria:
    • Diphtheria
    • Tuberculosis
    • Brucellosis
    • Psittacosis
    • Meningococcus
    • Mycoplasma
    • Group A streptococcus
    • Chlamydia species
    • Legionella pneumophila
    • Ehrlichia species
    • Staphylococcus aureus
  • Protozoa:
    • Leishmaniasis
    • Malaria
    • Toxoplasmosis
    • Babesiosis
    • Treponema cruzi (Chagas):
      • Most common cause of heart failure and myocarditis worldwide
      • Common in Central and South America
    • Trichinosis
    • Trypanosomiasis
  • Spirochetes:
    • Borrelia burgdorferi (Lyme)
    • Syphilis
  • Rickettsial:
    • Scrub typhus
    • Rocky Mountain spotted fever
    • Q fever
  • Fungal:
    • Candidiasis
    • Aspergillosis
    • Cryptococcosis
    • Histoplasmosis
    • Actinomycosis
    • Helminthic
    • Trichinosis
    • Echinococcosis
    • Schistosomiasis
    • Cysticercosis
  • Drugs:
    • Acetaminophen
    • Ampicillin
    • Chemotherapeutic agents (anthracyclines and ICI)
    • Cocaine
    • Hydrochlorothiazide
    • Lithium
    • Methyldopa
    • Penicillin
    • Sulfamethoxazole
    • Sulfonamides
    • Zidovudine
    • Radiation
    • Heavy metals
    • Hydrocarbons
    • Carbon monoxide
    • Arsenic
    • Vaccine (COVID-19):
      • Young males ages 12 yr to 40 yr at highest risk
  • Autoimmune disorders:
    • Systemic lupus erythematosus (SLE)
    • Wegener granulomatosis
    • Kawasaki disease
    • Giant cell arteritis
    • Sarcoidosis
  • Peripartum cardiomyopathy
  • Bites/stings:
    • Scorpion
    • Snake
    • Black widow venom

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