Myocarditis natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Varun Kumar M.B.B.S., Maliha Shakil, M.D. [2] Homa Najafi, M.D.[3]

Myocarditis is usually self limiting and is associated with a good prognosis especially if it is secondary to a viral infection. Patients rarely develop cardiac failure, pulmonary edema, arrhythmias, or cardiogenic shock. In some instances, myocarditis may be associated with sudden death. Patients with fulminant myocarditis have a good long term prognosis if they survive the acute phase of the disease. The prognosis of fulminant myocarditis is better than that of either acute myocarditis or giant cell myocarditis. The presence of syncope, pulmonary hypertension, biventricular dysfunction, left bundle branch block, q waves, AV block, and a left ventricular ejection fraction < 40% are associated with sudden death and cardiac transplantation. Complications of myocarditis include chronic dilated cardiomyopathy, heart block, congestive heart failure, pericarditis, ventricular dysfunction, arrythmias, and sudden cardiac death.

• The course of viral myocarditis is usually benign and the majority of cases of Coxsackie B virus infection are subclinical.
• Patients presenting with mild ventricular dysfunction secondary to viral myocarditis typically improve within weeks to months and rarely progress to severe ventricular dysfunction, heart block, arrhythmias, or even sudden cardiac death.
• Among patients who present with more advanced left ventricular dysfunction; 50% of patients develop chronic ventricular dysfunction and 25% have spontaneous improvement in ventricular function while the remaining 25% progress to transplantation or death.^[1][2][3]

• Complications of myocarditis include:^[1][2][3]
  • Chronic dilated cardiomyopathy
  • Heart block
  • Congestive heart failure
  • Pericarditis
  • Ventricular dysfunction
  • Arrythmias
  • Sudden cardiac death

• An endomyocardial biopsy is usually obtained in patients presenting with advanced heart failure or arrhythmias. The endomyocardial biopsy can shed light on the prognosis by ascertaining the underlying cause and the histopathologic severity of the disease.

• The markers which can be associated with poor prognosis include:^{[4][5][6][7][8][9]}
  • Fas and Fas ligand (cell death receptors) are associated with apoptotic death of myocytes and are a marker of cardiac dysfunction.
  • Antimyosin autoantibodies are associated with left ventricular systolic dysfunction and diastolic stiffness in patients with chronic myocarditis.
  • Persistence of the viral genome in the myocardium is associated with worsening of left ventricular ejection fraction.
  • Giant cell myocarditis (GCM) is a less common form of myocarditis which usually occurs in relatively young and healthy adults. It is associated with a poorer prognosis.
  • High levels of interleukin-10 in fulminant myocarditis patients at admission may be predictive of subsequent development of cardiogenic shock (requiring mechanical cardiopulmonary support system) and mortality.

• Despite its worrisome appearance, ST segment elevation suggestive of myocardial infarction is usually self-limited with no overt sequelae.^[10][11]
• In contrast, the presence of either left bundle branch block, q waves suggestive of old infarct or high degree AV block is associated with a poor long term prognosis, development of cardiac failure and the need for cardiac transplantation.

• The clinical manifestations which can associated with poor prognosis (associated with death or cardiac transplantation) include: ^[12][13]
  • Syncope
  • Bundle branch block
  • Ejection fraction <40%
  • Pulmonary hypertension
  • Biventricular dysfunction

• The prognosis in patients with new onset heart failure depends on the degree of ventricular dysfunction.^[1][14]
• The majority of myocarditis patients recover well with treatment. However, approximately 25% of patients develop chronic ventricular dysfunction and 25% of patients will continue to deteriorate.

• In a small series of 15 patients with fulminant myocarditis, 14(93%) survived for 11 years without the need for cardiac transplantation. This suggests that patients with fulminant myocarditis have a good long term prognosis if they survive the acute phase of the disease. In the same series, 132 patients met the criteria for acute myocarditis and 60(45%) of these patients were alive at the end of 11 years without having received a cardiac transplant.^[15]

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