Myocarditis risk factors: who is more likely

What myocarditis is

Heart inflammation is the body's reaction to an infection or injury to the heart. It can affect the lining of the heart or its valves (endocarditis), the heart muscle itself (myocarditis) or the tissue around the heart (pericarditis) (NHLBI). This page covers myocarditis. See pericarditis risk factors and endocarditis risk factors for the other two types.

Myocarditis can lead to heart failure, heart rhythm problems or, rarely, cardiogenic shock, which happens when the heart suddenly cannot pump enough blood to the body's tissues and organs (NHLBI).

What causes it

NHLBI lists these causes (NHLBI):

• Viruses are the most common cause of myocarditis and pericarditis. Examples NHLBI names are SARS-CoV-2 (the virus that causes COVID-19), adenovirus, coxsackievirus (including hand, foot, and mouth disease), herpes virus, influenza and parvovirus B19. Viruses may infect the heart muscle tissue and cause the immune system to react.
• Parasites can also cause myocarditis. One example is the parasite that causes Chagas disease, a serious health problem in Latin America.
• Fungi such as yeast or mold are rare causes. These infections are more common in people whose immune systems are weak from conditions such as HIV/AIDS, cancer or diabetes.
• Autoimmune diseases such as rheumatoid arthritis and lupus may cause myocarditis.
• Medicines. Side effects of some medicines may lead to myocarditis, pericarditis or both. NHLBI lists antibiotics, antidepressants, benzodiazepines (tranquilizers), diuretics, heart medicines, psychiatric medicines, seizure medicines and weight-loss medicines.
• Vaccines. Rarely, an allergic reaction to a vaccine can lead to myocarditis.

Who is more likely to get it

NHLBI lists these risk factors (NHLBI):

• Age. Myocarditis can affect all ages, but it occurs more often in young adults.
• Sex. Heart inflammation is more common in men than in women, except when it is caused by autoimmune diseases such as lupus and rheumatoid arthritis, which are more common in women.
• Genes and family history. Your genes may play a role in how your body responds to infection and inflammation and whether you get myocarditis. Rare inherited conditions that affect how the body controls inflammation, such as familial Mediterranean fever and tumor necrosis factor receptor-associated periodic syndrome (TRAPS), can raise the risk.
• Lifestyle. Drinking too much alcohol, and using cocaine, amphetamines or recreational drugs injected into the veins.
• Medical conditions: diabetes, which can make infections more likely; eating disorders such as anorexia; HIV/AIDS, which may lead to myocarditis through infections, poor nutrition and certain treatments; skin disorders such as burns or chronic infections; and poor dental health.
• Medicines that lower the immune system. Some medicines used to treat cancer and other conditions by lowering the body's natural defenses may damage the heart muscle and cause myocarditis.
• Procedures to treat other conditions, such as implanting a pacemaker or defibrillator, carry a risk of infection that can lead to heart inflammation.

Apart from the lines that name myocarditis, NHLBI lists these for heart inflammation as a whole, and it gives no score (NHLBI).

Symptoms

You may have no symptoms, or you may not notice them because the symptoms of the infection that caused the myocarditis can hide them. Symptoms differ from person to person and depend on the cause, but NHLBI lists (NHLBI):

• Chest pain
• Fatigue
• Trouble breathing
• Abnormal heart rhythms, called arrhythmias
• Fever
• No longer being able to exercise
• Rash

NHLBI's symptoms page also names the feeling of a racing or pounding heart (NHLBI).

If a virus causes heart inflammation, you may have a cough, runny nose or stomach and bowel symptoms a few weeks before other symptoms (NHLBI).

How it is diagnosed

Often there are no physical signs. A provider may use heart tests such as an ECG, an echocardiogram, a cardiac MRI and a chest x-ray, and blood tests for C-reactive protein and troponin. If the results are unclear, a provider may take a small piece of heart muscle to look at (endomyocardial biopsy), but this is rare (NHLBI).

Can it come back?

Yes. NHLBI says that in people with myocarditis, the disease can return many years after the first episode (NHLBI).

Can you prevent it?

NHLBI says many causes of myocarditis are hard or impossible to avoid or prevent. Managing risk factors for diseases such as HIV, and avoiding substances such as amphetamines and cocaine, may help prevent myocarditis (NHLBI).

For other diseases of the heart muscle, see cardiomyopathy risk factors.

Common questions

What is the most common cause of myocarditis?

NHLBI says viruses are the most common cause of myocarditis and pericarditis (NHLBI).

Who gets myocarditis most often?

It occurs more often in young adults, and heart inflammation is more common in men than in women (NHLBI).

Can a vaccine cause myocarditis?

NHLBI says that, rarely, an allergic reaction to a vaccine can lead to myocarditis (NHLBI). If you have questions about a vaccine, ask your provider.