Tests to diagnose myocarditis include: Blood tests. Blood tests are usually done to check for signs of a heart attack, inflammation and infection. A cardiac enzyme test can check for proteins related to heart muscle damage. Antibody blood tests may help determine if you had an infection linked to myocarditis. Electrocardiogram (ECG or EKG).

https://www.mayoclinic.org/diseases-conditions/myocarditis/diagnosis-treatment/drc-20352544