Inflammation of the heart muscle (myocardium) is most commonly caused by viral infections. Its symptomatic presentation can greatly vary. Mild fatigue and malaise on the light end but ranging to chest pain, arrhythmias, and rarely cardiogenic shock and death. Coxsackievirus, parvovirus, and herpes were the usual culprits, but positively identifying the cause of the inflammation would prove elusive in most cases. Drugs can also be the source; referred to as toxic myocarditis, the offending agent can range from cocaine to prescription products like lithium, phenothiazines, and tricyclic antidepressants. Myocarditis is certainly associated with COVID infection. One study showed 30% of patients had signs of myocarditis with cardiac imaging. Rarely it comes as a side effect of vaccination. It is a serious condition that needs to be identified and treated quickly. Chronic myocarditis over time may lead to anatomic changes in the heart muscle that predispose the patient to ventricular dysrhythmias.

The definitive diagnosis for myocarditis would be an EMB (endomyocardial biopsy). That procedure can be a bit intrusive on living patients. Even though it can be done safely, it is not without risk. So most commonly done to aid in diagnosis is the ECG or EKG electrocardiogram, which will reveal sinus tachycardia and ST segment and T wave changes. Further imaging studies like an echocardiogram or a cardiac MRI can help confirm the diagnosis. Elevated biomarkers that can indicate myocarditis include troponin, C reactive protein, creatine kinase, and white blood cells.