Signs and Symptoms of Myocarditis

Medically reviewed by Angela Ryan Lee, MD

Myocarditis is the inflammation of the heart muscle—also known as the myocardium. Symptoms of myocarditis vary widely, depending on the extent and severity of inflammation that you're experiencing and the underlying cause of your condition. It's worth noting that not everyone with myocarditis develops symptoms. When symptoms do occur, they may include fatigue, shortness of breath, chest pain, heart palpitations, and lightheadedness that can range from mild to severe.

Symptoms of myocarditis can develop suddenly or gradually over time, depending on the cause. For example, symptoms of myocarditis that develop after a viral infection generally begin within a few days or weeks following a viral infection (e.g., COVID-19 or influenza). Many people also report flu-like symptoms like fever, nausea, vomiting, cough, and fatigue before developing myocarditis symptoms.

This condition can be acute (short-term) and resolve quickly, subacute (lasting weeks or months), or chronic (lasting a few months or longer). In some cases, inflammation causes heart damage, interfering with your heart’s electrical system and reducing its ability to pump blood. This can lead to heart failure and other serious heart conditions, so knowing the warning signs is essential.

Common Symptoms

Symptoms of myocarditis vary from person to person. Some people experience mild symptoms, while others may have more severe symptoms that require immediate treatment. The most common symptoms of myocarditis include:

• Chest pain: A sensation of tightness, squeezing, or pressure in the chest that may feel like a heart attack. Chest pain may worsen with activity (e.g., exercise) or while lying down.

• Shortness of breath: Difficulty catching your breath or feeling like you can’t get enough air is especially common after exercise or when lying down.

• Fatigue: Feeling unusually tired and lacking energy can occur with myocarditis if the heart has to work harder to pump blood throughout the body.

• Heart palpitations: You may feel like your heart is racing, fluttering, skipping beats, or pounding. This can occur when inflammation interferes with the heart’s electrical system that regulates your heartbeat.

• Exercise intolerance: Some people with myocarditis may have trouble exercising or engaging in physical activity due to symptoms like shortness of breath and chest pain.

Less Common Symptoms

Myocarditis is usually mild—and most people do not experience long-term health problems. If myocarditis affects your heart’s electrical conduction system that regulates your heart rhythm, you may experience recurrent or chronic arrhythmia (irregular heartbeat). In about 25% of cases, inflammation arrhythmias or problems with the heart muscle can cause your heart to work harder than normal.

Some less common symptoms of myocarditis that may indicate that your heart is working harder include:

• Lightheadedness or fainting: Irregular heartbeat (e.g., fluttering or pounding) can lead to lightheadedness or fainting.

• Swelling: Experiencing some swelling in the legs, ankles, and feet is a sign that the heart is damaged and struggling to pump blood to the rest of the body.

• Rash: Myocarditis that develops due to a hypersensitive reaction to certain medications (e.g., antibiotics or antiseizure medications) can cause a widespread rash with or without bumps. This rash may first appear on the arms, trunk, or face and spread to other body parts if your condition worsens.
  

Rare Symptoms

Though rare, severe myocarditis can cause life-threatening complications, including severe heart failure and cardiogenic shock. Cardiogenic shock occurs when the inflammation damages the heart so severely that it cannot effectively pump oxygen-rich blood to the body’s organs.

Cardiogenic shock is a medical emergency and requires prompt treatment. Symptoms may include:

• Cold, clammy, or pale skin

• Decreased urination

• Fast breathing or severe shortness of breath

• Weak pulse

• Rapid heart rate

• Agitation, confusion, or restlessness

• Loss of consciousness

If you have symptoms of cardiogenic shock, it's essential to visit an emergency room, call 911, or contact your healthcare provider or cardiologist (a doctor who specializes in heart conditions) immediately.

Symptoms in Children

Myocarditis is more common in adults than children, though children are more likely to develop acute or sudden-onset myocarditis following a viral infection. If a child develops myocarditis, they may experience the following symptoms:

• Cough

• Fatigue

• Fever

• Chest pain
  

• Nausea and vomiting

• Heart palpitations

• Abdominal pain

• Shortness of breath

• Diarrhea

When to Contact a Healthcare Provider

Your overall health and well-being depend on a healthy heart, which supplies blood and oxygen to your body’s tissues and vital organs. That’s why it’s crucial to contact a healthcare provider if you develop symptoms of myocarditis, such as shortness of breath, fatigue, or chest pain—especially if you’ve recently had a viral or bacterial infection.

Some myocarditis symptoms are life-threatening and require emergency medical care. Call 911 or go to the hospital immediately if you experience any of the following symptoms:

• Severe chest pain

• Difficulty breathing

• Cold, pale skin

• Rapid or abnormally slow heartbeat

• Fainting

• Confusion or agitation

• Decreased urination (peeing less frequently or in abnormally small amounts)

Questions to Ask Your Provider

Experiencing symptoms of myocarditis can be unsettling. Seeking medical attention can address your concerns. You can get more information about the condition by asking your healthcare provider the following questions:

• Which tests are available to diagnose myocarditis?

• What other conditions could be causing my shortness of breath and chest pain?

• If I receive a diagnosis for myocarditis, what does treatment look like?

• How long will it take me to recover if I have myocarditis?

• Are there lifestyle changes I should make to lower my risk of complications?
  

A Quick Review

Myocarditis is the inflammation of the heart muscle. While some people may develop no symptoms, others may experience chest pain, fatigue, shortness of breath, and heart palpitations. Symptoms of myocarditis can develop suddenly or gradually. See a healthcare provider if you experience any myocarditis symptoms, even if they are mild. While most people recover with no ongoing health problems, myocarditis can sometimes be life-threatening and requires medical attention and treatment to prevent complications.

Frequently Asked Questions

When should I suspect myocarditis?

You may suspect myocarditis if you recently had an infection and develop symptoms like shortness of breath during and after physical activity or when lying down, fatigue, heart palpitations, and chest pressure or pain.

How do you detect myocarditis?

Myocarditis testing requires a physical examination and diagnostic tests from a healthcare provider. Your healthcare provider may order blood tests, a chest X-ray, an electrocardiogram (ECG/EKG), magnetic resonance imaging (MRI), echocardiography, and cardiac biopsy to diagnose myocarditis.

What is the main cause of myocarditis?

Viral infections (e.g., influenza, COVID-19) are the leading cause of myocarditis. Other causes include bacterial and fungal infections, autoimmune and inflammatory conditions, certain cancer treatments (e.g., radiation), and some medications, such as antibiotics, psychiatric drugs, and diuretics.

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