Myocarditis

You may not have any symptoms of myocarditis, or you may not notice any symptoms since they could be overshadowed by symptoms of the infection that caused the myocarditis. Myocarditis symptoms will depend on the level of inflammation and whether the pericardium is affected (myopericarditis). Myocarditis can lead to heart failure, rhythm disturbances or rarely cardiogenic shock (a devastating condition that occurs when your heart suddenly cannot pump enough blood to your tissues and organs).  

Symptoms can be very different from person to person depending on the cause and severity of myocarditis but include: 

• Chest pain
• Trouble breathing
• Exercise intolerance (no longer being able to exercise)
• Abnormal heart rhythms, called arrhythmias
• Fatigue
• Fever
• Rash

Sometimes, the cause of myocarditis is unknown. However, regardless of the specific cause, a healthcare provider can actively and effectively treat myocarditis. Myocarditis can be caused by infections or other factors unrelated to infections.

• Infective myocarditis is caused by infections from viruses (such as COVID-19, HIV, parvovirus B19, or human herpes virus 6), bacteria, fungi or parasites.
• Some non-infective causes include medicines (antibiotics such as penicillin, psychiatric medicines such as clozapine, and diuretics such as furosemide and hydrochlorothiazide), autoimmune conditions, other medical conditions such as giant cell myocarditis and some cancer treatments such as immune checkpoint inhibitors or radiation. 

Myocarditis and COVID-19 – Myocarditis is a rare complication of COVID-19. It is more common in some groups of people, such as:

• People who are hospitalized for complications related to COVID-19. About 1 in 5 people who are hospitalized with COVID-19 develop heart problems, including myocarditis as well as acute coronary syndrome, arrhythmias and blood clots
• People who have other health conditions like high blood pressure, diabetes and obesity
• Older adults
• Men

Researchers are still working to find the exact link between COVID-19 infection and myocarditis. Many people with COVID-19-induced myocarditis could be treated with supportive care such as fluids, beta-blockers, diuretics. If this treatment is unsuccessful, other medicines like vasopressors, steroids and antivirals could be used.

Myocarditis is an extremely rare complication of the COVID-19 vaccine (affects less than 20 people per million COVID-19 vaccinations). Myocarditis from the COVID-19 vaccine is less severe than myocarditis caused by COVID-19 itself. The benefits of getting vaccinated outweigh the small risk of vaccine-related myocarditis. 

Often, there are no physical signs of myocarditis. Your healthcare provider will diagnose myocarditis using tests and procedures. Common blood tests include your blood counts, C-reactive protein and troponin. A chest x-ray is often ordered, especially if someone is having trouble with breathing. Heart tests may include an EKG, an echocardiogram, cardiac CT or magnetic resonance imaging (MRI).  

In some cases, your provider may need to run more tests to find the exact cause. This could include a procedure called endomyocardial biopsy, especially if other test results are inconclusive and identifying the underlying cause is crucial for selecting the appropriate treatment. During an endomyocardial biopsy, a physician passes equipment through catheters to remove a small sample of heart muscle tissue, which is then analyzed to identify the underlying problem. This procedure is rarely performed and is usually not necessary for treatment. When needed, the procedure is performed in a small number of specialized centers.