Prognosis

Given the limitations in current methods of diagnosing myocarditis, it is not surprising that its natural history and associated prognosis are as varied as its clinical presentations. Despite this, multiple factors have been linked to a favourable or poorer outcome. A definite association exists between the myocarditis-associated risk factor or specific type of myocarditis and the prognosis of the patient.[5]​ Also, the severity of illness at presentation tends to correlate with long-term outcome.

According to the American College of Cardiology, key risk factors for adverse prognosis in patients with myocarditis include:[56]

  • Symptomatic heart failure

  • Cardiogenic shock

  • Electrical instability (recurrent ventricular arrhythmia or advanced atrioventricular block)

  • Biventricular reduced ejection fraction

  • Late gadolinium enhancement on cardiac MRI

  • Giant cell myocarditis

Endomyocardial biopsy (EMB) DNA PCR persistence of cardiotropic viral genome

The prognosis of patients in whom the EMB DNA polymerase chain reaction analysis is positive for a cardiotropic viral genome has been studied. Those who have persistently positive viral genome analysis on EMB demonstrate worsening left ventricular (LV) ejection fraction and outcome when compared with those who test negative on subsequent EMBs.[118]

Fulminant myocarditis

One 11-year study of patients presenting with myocarditis showed a 93% survival free of heart transplantation in patients with fulminant myocarditis as opposed to 45% in patients who presented with acute myocarditis.[119] Reduced biventricular systolic function, ventricular arrhythmia, and heart block associated with fulminant myocarditis at presentation are important adverse risk factors.[56]​

Giant cell myocarditis

Despite modest improvement in mortality with immunosuppressive therapy, patients with giant cell myocarditis have the worst outcomes with a median survival of 5.5 months from the onset of heart failure symptoms.[97]

Presentation mimicking MI

Patients presenting with chest pain and ECG changes similar to those seen in ST-segment elevation myocardial infarction have almost uniform recovery without any residual cardiac dysfunction.[17]

Histological resolution of myocardial inflammation

Patients with histological resolution of myocardial cellular infiltration on repeat EMB tend to have improvement in cardiac function and a favourable clinical outcome.[120]

Serum immunological markers

Patients with idiopathic cardiomyopathy and elevated levels of serum tumour necrosis factor (TNF)-alpha receptor-1 and fas at presentation have a worse clinical course and are more likely to not recover LV function than those with lower levels.[121]

Cardiac MRI findings

A normal cardiac MRI indicates a favourable long-term prognosis, regardless of clinical and other findings. Myocardial oedema without fibrosis is also associated with a positive prognosis.[57]

Conversely, a significant amount of early and late gadolinium enhancement correlates with a poor prognosis.[57]

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