Myocarditis natural history


 * Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S.

Overview
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 left bundle branch block, q waves, AV block, syncope and a left ventricular ejection fraction < 40% are associated with sudden death and cardiac transplantation.

Natural History and Complications
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.

Endomyocardial Biopsy
Endomyocardial biopsy remains the gold standard diagnostic tool in patients with myocarditis. An endomyocardial biopsy is usually obtained in patients presenting with advanced heart failure or arrhythmias. Endomyocardial biopsy can shed light on the prognosis by ascertaining the underlying cause and the histopathologic severity of the disease.

Fas and Fas ligand
Fas and Fas ligand (cell death receptors) are associated with apoptotic death of myocytes and are a marker of cardiac dysfunction. A study evaluating the association of gene expression with myocardial recovery in patients with recent-onset cardiomyopathy demonstrated that patients in the highest tertile of Fas expression had minimal improvement at six months when compared with patients in the intermediate and lowest tertiles.

Antimyosin Autoantibodies
Antimyosin autoantibodies are associated with left ventricular systolic dysfunction and diastolic stiffness in patients with chronic myocarditis.

Persistence of the Viral Genome
Persistence of the viral genome in the myocardium is associated with worsening of left ventricular ejection fraction.

Giant Cell Myocarditis
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. In a series of 63 patients with giant-cell myocarditis, death or cardiac transplantation occurred in 89% of patients and the median survival was 5.5 months. Among the 34 patients who underwent cardiac transplantation, 9 patients (26%) died during an average follow-up of 3.7 years and 5 died within 30 days of cardiac transplantation.

Prognostic Implications of EKG Changes
Despite its worrisome appearance, ST segment elevation suggestive of myocardial infarction is usually self-limited with no overt sequelae.

In contrast, the presence of either left bundle branch block, q waves suggestive of old infarct or high degree AV block are associated with a poor long term prognosis and are associated with the development of cardiac failure and cardiac transplantation.

Clinical Predictors of Prognosis
The development of syncope, bundle branch block, ejection fraction <40% and pulmonary hypertension are known to be poor predictors of myocarditis and are associated with death or cardiac transplantation.

Prognosis Associated with Left Ventricular Dysfunction
The prognosis in patients with new onset heart failure depends on the degree of ventricular dysfunction. 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.

Prognosis Associated with Fulminant Myocarditis vs Acute Myocarditis
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.

Prognostic Biomarkers
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.