Myocarditis

Myocarditis: Excerpt from The 5-Minute Pediatric Consult

Bradley S. Marino, MD

Myocarditis - BASICS

Myocarditis - description

Myocardial cell injury with degeneration or necrosis with inflammatory infiltrate not caused by ischemia

Myocarditis - epidemiology

Cardiovascular complications are a rare complication of viral infection, despite their ubiquitous nature.

Myocarditis - incidence

• True incidence of acute myocarditis is difficult to estimate because of the wide range in clinical severity.
• Estimates of the incidence of clinically significant disease in tertiary care facilities have been as high as 0.3% in some case series.
• May account for >15% of cases of sudden infant death syndrome and 60% of cases of peripartum cardiomyopathy

Myocarditis - prevalence

More prevalent in the summer months, likely owing to the higher prevalence of enteroviral infections during this season

Myocarditis - risk factors

• Exposure to infectious agents, drugs, toxins, and systemic diseases
• Drug abuse
• Systemic autoimmune disease

Myocarditis - pathophysiology

• Although many agents, including viruses, may exert direct cytotoxic effects, subsequent autoimmune response appears to be the major factor leading to cellular injury. This theory is supported by studies linking persistence of viral RNA in the myocardium with induction of autoantibodies and resultant ventricular dysfunction.
• Recent work has identified the coxsackie-adenovirus receptor, offering both insight into the cardiac tropism of these agents and an explanation for the infrequent occurrence of viral myocarditis despite the ubiquitous nature of the agents:
  • Regardless of the cause, symptom severity increases with worsening ventricular function.
  • Fulminant myocarditis may be characterized by both severe systolic and diastolic dysfunction.
  • Progressive left ventricular systolic dysfunction may lead to hypotension, acidosis, and end-organ hypoperfusion.
  • Left ventricular diastolic dysfunction may result in elevated left ventricular end diastolic pressures, leading to pulmonary venous and arterial hypertension, with possible concomitant pulmonary edema.

Myocarditis - etiology

• Idiopathic: Most common form
• Causes of myocarditis may include various infections, drugs, toxins, and systemic diseases: Viral bacterial, rickettsial, fungal, and parasitic organisms have been linked to myocarditis.
• In the US and Europe, viruses are the most frequent infectious cause of myocarditis:
  • Recent studies suggest that adenovirus is the most common viral agent, with enteroviruses (e.g., coxsackievirus B) also playing a prominent role.
  • Other viruses include Epstein-Barr virus, herpes simplex virus, parvovirus B19, human immunodeficiency virus, cytomegalovirus, influenza A/B, and hepatitis C virus.
  • Worldwide, Trypanosoma cruzi (Chagas disease) and Corynebacterium diphtheria (diphtheria) are common causes.
• Recent reinitiation of smallpox vaccination has resulted in recurrence of vaccinia.
• Among the drugs and toxins, cocaine abuse and enterotoxins (occurring during septic shock) have been associated with acute onset of cardiac dysfunction.
• Giant cell myocarditis is a rare, very severe form, associated with various systemic autoimmune diseases, including systemic lupus erythematosus, rheumatic fever, and Kawasaki disease.

Myocarditis - DIAGNOSIS

Myocarditis - signs & symptoms

• Prodromal:
  • Antecedent flulike illness
  • Gastroenteritis
  • Rheumatologic symptoms
  • Fever
• Left-sided heart failure:
  • Exercise intolerance
  • Easy fatigability
  • Dyspnea
  • Orthopnea
  • Anorexia, loss of appetite/poor feeding, early satiety
  • Emesis (especially in children)
• Right-sided heart failure:
  • Abdominal pain/cramping
  • Swelling of abdomen/lower extremities
  • Loose stools

Myocarditis - history

• Duration of symptoms
• Travel history
• Family history

Myocarditis - physical exam

Any of the following may be present:

• Pulmonary:
  • Rales
  • Tachypnea
  • Retractions
• Cardiovascular:
  • Jugular venous distention
  • Normal to hyperdynamic precordium with or without right ventricular heave
  • Lateral displacement of the point of maximal impulse (PMI)
  • Tachycardia: Arrhythmia (atrial and/or ventricular ectopy may be present), accentuation of 2nd heart sound (secondary to pulmonary artery hypertension), murmur (mitral and/or tricuspid insufficiency), gallop
• Abdomen: Hepatomegaly
• Extremities:
  • Weak pulses
  • Poor capillary refill
  • Cool extremities

Myocarditis - tests

Despite limited sensitivity and specificity, endomyocardial biopsy, using the Dallas criteria for histopathologic classification, remains the gold standard for confirming the diagnosis of acute myocarditis:

Dallas Criteria for Diagnosis of Myocarditis:

Recent studies, however, suggest that isolation of viral genome from tracheal aspirates in the proper clinical setting may have a diagnostic accuracy similar to that of endomyocardial biopsy (which would eliminate the risk of cardiac perforation with the procedure). Other studies supportive of the diagnosis may include:

• EKG:
  • Highly variable findings may include sinus tachycardia, low voltage QRS, ST segment elevation, flattening or inversion of the T wave, prolongation of the QT interval, and arrhythmias (premature atrial contractions/supraventricular tachycardia, or premature ventricular contractions/ventricular tachycardia).
• Echocardiogram:
  • Impaired systolic and/or diastolic ventricular function
  • Cardiac chamber enlargement
  • Valvar insufficiency (particularly mitral valve insufficiency)

Myocarditis - lab

• ESR, C-reactive protein level: Elevated
• Creatine kinase MB fraction and Troponin T and I levels: Elevated
• Cultures (bacterial, viral, fungal) of blood, urine, stool, and nasopharynx may be considered.
• Acute and convalescent serologic studies may be considered for selected antibody studies.

Myocarditis - imaging

• Chest radiograph:
  • Cardiomegaly and varying degrees of pulmonary edema
  • Possible pleural effusions
• Autoimmune (gallium-67) scintigraphy: Sensitive, but not specific for acute myocarditis
• Contrast-enhanced MRI

Myocarditis - differencial diagnosis

• Severe left-sided obstructive heart lesions:
  • Mitral stenosis
  • Valvar aortic stenosis
  • Coarctation of the aorta
• Congenital coronary artery anomalies: Anomalous left coronary artery from the pulmonary artery and other coronary variants
• Incessant arrhythmias:
  • Incessant supraventricular tachycardia
  • Ventricular tachycardia
• Metabolic disorders: Selenium and carnitine deficiency
• Mitochondrial disorders
• Genetic syndromes:
  • Muscular dystrophies
  • Familial cardiomyopathies

Myocarditis - TREATMENT

Myocarditis - general measures

Major advances in therapy have been realized over the last decade:

• Bed rest and limited activity (during acute phase)
• Standard medical regimens:
  • Inotropic support with Milrinone, and dopamine or Dobutamine; if epinephrine is required, mechanical support should be considered.
  • Diuretics
  • Angiotensin-converting enzyme (ACE) inhibitors
  • Beta-blockers with or without digitalis
  • Antiarrhythmics (in cases of hemodynamically significant dysrhythmias)
  • Immunosuppression
  • Anticoagulation with heparin acutely and aspirin and/or coumadin chronically for patients with severe myocardial depression and ventricular dilation
  • Mechanical ventilation in patients with respiratory failure secondary to myocardial failure
  • Mechanical support (in patients with rapidly progressing, severe heart failure; used as a bridge to transplantation): Left ventricular or biventricular assist devices, extracorporeal membrane oxygenation (ECMO)
  • Rescue therapy: Cardiac transplantation

Myocarditis - activity

Bed rest or nonexertional

Myocarditis - medication

Immunosuppression:

• High-dose gamma globulin (2 g/kg IV immunoglobulin [Ig] over 24 hours) during the acute phase has been associated with improved recovery of left ventricular function and with a tendency for better survival during the 1st year after presentation.
• Steroids, azathioprine, calcineurin inhibitors, cyclosporine, cyclophosphamide, and other immunosuppressive medications have all been suggested as effective agents, although insufficient evidence of therapeutic benefit is currently available to recommend routine use.

Myocarditis - surgery

Cardiac transplantation as indicated

Myocarditis - FOLLOW UP

• Patients with acute myocarditis require close and coordinated follow-up between the pediatric cardiologist and the general pediatrician.
• Pediatric cardiology follow-up should be based on the severity of clinical symptoms, the degree of myocardial depression, associated arrhythmias, and longitudinal changes in cardiac function. Additional testing (as described previously) would be expected to monitor for resolution of any inflammatory response and cardiac performance.

Myocarditis - prognosis

• Statistics are hampered by the lack of complete ascertainment of all cases of acute myocarditis, with many patients likely exhibiting only mild symptoms, which spontaneously resolve.
• Of those patients who present with acute left ventricular failure, ~1/3 will make a full recovery, 1/3 will develop a stable dilated cardiomyopathy, and 1/3 will progress to irreversible ventricular failure, necessitating either chronic, mechanical support or cardiac transplantation.
• A recent report in adults suggests that those presenting with fulminant myocarditis are far more likely to demonstrate recovery of ventricular function than those presenting with subacute or chronic myocarditis (without severe initial ventricular impairment) alone.
• Giant cell myocarditis represents a unique subgroup with a particularly poor prognosis. In one series, >70% of patients had either died or been transplanted at 1 year from the time of diagnosis.

Myocarditis - complications

• Acidosis
• End-organ hypoperfusion
• Pulmonary venous and arterial hypertension
• Pulmonary edema
• Irreversible ventricular failure

Myocarditis - patient monitoring

• Clinical changes in cardiac function
• Effects of the illness on other systems:
  • Nutritional status
  • Growth
  • Development
  • Comorbid illnesses

Myocarditis - bibliography

1. Batra AS, Lewis AB. Acute myocarditis. Curr Opin Pediatr. 2001;13:234–239.
2. Bowles NE, Ni J, Kearney DL, et al. Detection of viruses in myocardial tissues by polymerase chain reaction: Evidence of adenovirus as a common cause of myocarditis in children and adults. J Am Coll Cardiol. 2003;42:473–476.
3. Checchia PA, Kulik TJ. Acute viral myocarditis: Diagnosis. Pediatr Crit Care Med. 2006;7(Suppl 6):S8–S11.
4. Drucker NA, Colan SD, Lewis AB, et al. Gamma-globulin treatment of acute myocarditis in the pediatric population. Circulation. 1994;89:252–257.
5. Feldman AM, McNamara D. Myocarditis. N Engl J Med. 2000;343:1388–1398.
6. Feltes T, Adatia I. Immunotherapies for acute viral myocarditis in the pediatric patient. Pediatr Crit Care Med. 2006;7(Suppl 6):S17–S20.
7. Schwartz SM, Wessel DL. Medical cardiovascular support in acute viral myocarditis in children. Pediatr Crit Care Med. 2006;7(Suppl 6):S12–S16.
8. Shekerdemian L, Bohn D. Acute viral myocarditis: Epidemiology and pathophysiology. Pediatr Crit Care Med. 2006;7(Suppl 6):S2–S7.

Myocarditis - CODES

Myocarditis - icd9

422.91 Myocarditis idiopathic

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Autoimmune Myocarditis

• Back to disease: Autoimmune Myocarditis: Introduction
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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