12th March 2024

Diagnosis

Blood tests typically show raised inflammatory markers (ESR and CRP). Cardiac enzymes troponin and CK-MB are also raised, reflecting myocardial injury. Of note, normal troponin values do not exclude myocarditis. 

Common ECG findings in myocarditis include ST segment elevation and T wave inversion. Conduction abnormalities such as AV blocks will be evident on the ECG. Prolongation of the QRS is an independent risk factor for mortality. 

Where myocarditis is suspected, patients should have an echocardiogram with subsequent serial echocardiograms as follow-up. Typical findings include regional wall motion abnormalities, depressed right or left ventricular ejection fraction, pericardial effusion or global ventricular dysfunction. 

Coronary angiogram is recommended in all patients to exclude coronary artery disease as a cause of the clinical picture. Cardiovascular magnetic resonance (CMR) imaging is useful in providing a non-invasive study which can aid in the diagnosis of myocarditis. Typical features diagnostic of myocarditis include increased oedema and late gadolinium enhancement.  

The gold standard for definitive diagnosis of myocarditis is endomyocardial biopsy (EMB). This has the added value that it can help identify the aetiology of myocarditis. Samples from EMB are analysed by RT-PCR amplification of the viral genomes and immunohistochemistry.