Symptoms of Myocarditis

Myocarditis is an inflammatory disease affecting the heart muscle (or myocardium). It is most often caused by infections, immune diseases, or toxins. This inflammation reduces the ability of the heart muscle to contract normally. In severe cases, myocarditis can produce permanent heart damage, including dilated cardiomyopathy and heart failure.

Symptoms of Myocarditis

The symptoms caused by myocarditis can vary tremendously in severity. Some people with this condition have symptoms that are barely noticeable, while others will be more profoundly affected.

The degree of symptoms tends to correlate with the severity of inflammation present in the heart muscle. Mild symptoms are associated with milder cases of myocarditis, while severe symptoms usually reflect a significant inflammatory process.

In more significant cases actual cardiac symptoms appear, including chest pain. If the myocarditis becomes severe enough to cause heart failure, dyspnea (shortness of breath) and edema (swelling) of the legs and feet can occur, along with all the other problems one can experience with heart failure.

Occasionally myocarditis overwhelms the heart and produces rapid, severe, and irreversible heart failure.

Heart arrhythmias can occur during acute myocarditis. These arrhythmias can be of almost any type, including both the bradycardias (slow heart rhythms) and tachycardias (rapid heart rhythms), such as atrial fibrillation and ventricular tachycardia. These arrhythmias usually disappear once the acute myocarditis resolves.

What Causes Myocarditis?

Many causes of myocarditis have been identified. These include:

• Infections with numerous infectious agents, including viral infections, bacterial infections, Lyme disease, fungal disease, parasites, and toxoplasmosis
• Systemic immune or inflammatory diseases, including lupus, sarcoidosis, inflammatory bowel disease, postpartum cardiomyopathy (myocarditis after delivering a baby), and Grave's disease
• Toxins, including alcohol, cocaine, arsenic, carbon monoxide, and various medications
• Allergic reactions to numerous substances including antibiotics, insect or snake bites, or tetanus toxoid
• Radiation, including radiation therapy applied to the chest area, such as for breast cancer

Myocarditis and Covid-19

Since the start of the COVID-19 pandemic, researchers have published several studies on the connection between the virus and myocarditis.

One study found that between 2.4 and 4.1 out of 1,000 patients hospitalized for COVID-19 developed acute myocarditis, usually in the absence of pneumonia.

There has also been some research on the risk of myocarditis in those who received COVID vaccines. According to a July 2021 study, myocarditis was reported at a higher rate than expected among some people who received the Pfizer or Moderna vaccines. Most of the suspected cases developed after the second dose and were among males between 12 and 39 years old. Despite these cases, the study concluded that the benefits of the COVID-19 vaccine outweigh the rare risk of myocarditis.

How Is Myocarditis Diagnosed?

The diagnosis of myocarditis takes into account the patient’s symptoms and physical exam. Other tests include:

• Blood tests, which can indicate elevated cardiac enzymes, abnormal blood counts, viruses, along with other indicators
• Magnetic resonance imaging (MRI)
• A chest X-ray
• An echocardiogram to assess the extent of heart muscle damage
• Cardiac catheterization

Occasionally, a heart muscle biopsy is required to document the extent and type of inflammation present in the heart muscle.

How Is Myocarditis Treated?

The treatment of myocarditis is aimed first and foremost at identifying and treating the underlying cause.

For instance, it is critical to treat an underlying infection with the appropriate antibiotics, to aggressively treat an underlying autoimmune disorder, or to remove the source of toxin exposure (such as cocaine or alcohol).

If heart failure is present, aggressive treatment for heart failure consisting of some of the following medications may be used:

• Angiotensin-converting enzyme (ACE) inhibitor / angiotensin receptor blockers (ARBs)
• Beta blockers
• Diuretics
• Corticosteroids

In addition, people with acute myocarditis should avoid exercise or any unnecessary physical exertion to reduce the work of the heart during this acute phase.

With aggressive treatment, many people with myocarditis will recover completely. In some people, however, the recovery is not complete, and some degree of cardiac damage may be permanent. In addition, inflammation may smolder along for months or years, causing gradual worsening of cardiac function.

For this reason, anyone who has had myocarditis needs to be reevaluated every few months, and their physical activity may need to be limited until it is clear that the problem has fully resolved. Even at that point, people who have had myocarditis should be reexamined on an annual basis.

Summary

In most cases, myocarditis is a relatively mild and self-limited heart problem. But in some people, myocarditis can lead to significant heart failure, and it can do so either acutely or more gradually. With an accurate diagnosis, myocarditis can be treated to avoid serious complications.