Myocarditis

This page is for adult patients. For pediatric patients, see: myocarditis (peds)

Background

• Inflammatory (dilated) cardiomyopathy caused by necrosis of myocytes

Causes

• Infectious agents
  • Enterovirus (Coxsackie B) and adenovirus most common
  • Influenza A and B
  • Hepatitis B
  • Beta-hemolytic streptococcus
  • Mycoplasma
  • Mumps
  • CMV
  • Toxoplasma
  • Chagas (most common cause worldwide)
  • Trichinosis
  • Diphtheria
  • Lyme disease
  • COVID-19
• Drugs
  • Doxorubicin
  • Cocaine

Phases

• Acute
  • Viral cytotoxicity and focal necrosis
• Subacute
  • Host's humoral/immune response leading to further cell injury
• Chronic
  • Diffuse myocardial fibrosis and cardiac dysfunction

Clinical Features

• Typically young patients (20 - 50 years) with few risk factors for CAD
• Chest pain
• Pericardial friction rub
• Flu-like symptoms
  • Fever, fatigue, myalgia, nausea and vomiting
  • Tachycardia (out of proportion to fever)
  • Tachypnea
• New onset congestive heart failure
• Pediatric patients:
  • Grunting
  • Retractions
  • Ronchi
• Infants may have fulminant syndrome
  • Fever
  • Cyanosis
  • Respiratory distress
  • Tachycardia
  • Heart failure
  • Ventricular dysrhythmias

• Consider this diagnosis in the septic-appearing patient who gets WORSE after receiving IV fluids

Differential Diagnosis

Consider other causes of CHF

Chest pain

Critical

• Acute coronary syndromes (ACS)
  • STEMI
  • Non-STEMI
  • Unstable angina
• Aortic dissection
• Cardiac tamponade
• Coronary artery dissection
• Esophageal perforation (Boerhhaave's syndrome)
• Pulmonary embolism
• Tension pneumothorax

Emergent

• Cholecystitis
• Cocaine-associated chest pain
• Mediastinitis
• Myocardial rupture
• Myocarditis
• Pancreatitis
• Pericarditis
• Pneumothorax

Nonemergent

• Aortic stenosis
• Arthritis
• Asthma exacerbation
• Biliary colic
• Costochondritis
• Esophageal spasm
• Gastroesophageal reflux disease
• Herpes zoster / Postherpetic Neuralgia
• Hypertrophic cardiomyopathy
• Hyperventilation
• Mitral valve prolapse
• Panic attack
• Peptic ulcer disease
• Pleuritis
• Pneumomediastinum
• Pneumonia
• Rib fracture
• Stable angina
• Thoracic outlet syndrome
• Valvular heart disease
• Muscle sprain
• Psychologic / Somatic Chest Pain
• Spinal Root Compression
• Tumor

Evaluation

• ECG
  • Sinus tachycardia
  • Low voltages
  • Prolonged QTc
  • AV block
  • ST elevations (Usually >1 vessel distribution)
• Elevated troponin
• Echocardiography
  • Decreased LVEF
  • Global hypokinesis
  • Regional wall motion abnormalities
• Contrast MR
• Nuclear Study
  • Widespread uptake indicating myocyte necrosis
• Viral titres
• Endocardial biopsy: Gold standard, but rarely used

Management

• Acute phase
  • Antiviral agents (Pleconaril/Ribavirin) may be effective
  • COVID-related: limited/conflicting evidence regarding efficacy of high-dose steroids and/or IVIG
• Subacute phase
  • Studies have not shown efficacy of immunosupressants
  • Pediatric patients may receive high-dose IVIG
• Chronic phase
  • Treatment for CHF symptoms
  • Ventricular Assist Devices (VAD)
  • Cardiac transplant

Disposition

• If CHF is present, admit to monitored bed
• If hemodynamically unstable, admit to ICU

Prognosis

• Fulminant myocarditis has best prognosis
• Mortality: 20% 1 yr/ 50% 5 yr
• Children with 70% survival rate at 5 yrs
  

Complications

• Ventricular dysrhythmias
• LV aneurysm
• CHF

See Also

• Cardiomyopathy
• Pericarditis