Myocarditis

Myocarditis refers to inflammation of the myocardium. It has a wide range of presentations, anywhere from acute and fulminant to chronic.

As the cardiac conduction system is in the myocardium, myocarditis predisposes to arrhythmias. It also affects the myocardium’s ability to contract. It may mimic ACS.

Myocarditis is mostly a disorder of younger adults.

Etiology

• Viral (coxsackie) (most common)
• Bacterial (rheumatic fever)
• Autoimmune disorders
• COVID-19
• COVID-19 vaccines (rare)

Clinical features

Many are asymptomatic, and symptoms are highly variable. Some have preceding symptoms of viral infection.

• New onset or worsening heart failure
• Acute coronary syndrome-like symptoms (chest pain, dyspnoea)
• Arrhythmias

Diagnosis and evaluation

Troponins are elevated, as are inflammatory markers. ECG is often abnormal, but no findings are specific for myocarditis. ST-elevations and heart blocks are probably the most common. Echocardiography is important to determine the myocardial contractility and to exclude differential diagnoses.

MRI is usually sufficient to diagnose myocarditis. In doubtful cases, and endomyocardial biopsy can be performed, which may also provide information on the etiology.

Treatment

There is no specific treatment, except if there’s a treatable underlying cause. Most cases are self-limiting. Patients should be continuously monitored for arrhythmias by telemetry. The patient may require antiarrhythmics or treatment for heart failure. Unlike in pericarditis, NSAIDs cannot be used as they are not helpful and might even worsen outcomes.

Complications

• Cardiogenic shock
• Sudden cardiac death
• Secondary dilated cardiomyopathy