Myocarditis is simply defined as inflammation of the heart muscle. It’s typically caused by an infection from any number of pathogens. However, “there are many, many different causes,” says Dr. DeLisa Fairweather, Ph.D., Director of Translational Research for the Department of Cardiovascular Medicine at Mayo Clinic’s campus in Florida. “There are many viruses that cause it, as well as many types of bacteria, fungi, protozoa, parasites, toxins, and more.” Here, Fairweather and the Myocarditis Foundation describe some common causes and types of heart infection that you should be aware of.

Viral Heart Infections

By far, the most common type of heart infection that can lead to myocarditis is viral. When the body detects viruses in its system, it produces cytokines to fight them. These tiny proteins are designed to interfere with the virus’s signaling abilities and keep it from reproducing. The downside, however, is that cytokines can also inflame the heart.

The most common virus to cause myocarditis in the United States is coxsackievirus. This is a type of enterovirus that naturally affects the intestines, resulting in stomach flu. If it escapes the intestines and reaches the heart, however, coxsackievirus can cause myocarditis. Meanwhile, in Europe, the most common causes of myocarditis are parvoviruses and adenoviruses. In Asia, the common cause is Hepatitis C virus, while Africa sees many infections from HIV. Currently, however, the most frequent originator of myocarditis worldwide is the SARS-CoV-2, the virus responsible for COVID-19.

Bacterial Heart Infections

Bacterial heart infections aren’t as common as viral ones. Most often, bacteria in the bloodstream simply pass through without causing an infection. Certain kinds of bacteria can latch on to already-damaged parts of the heart, however. Usually, this is the result of bacteria that lives in the mouth, throat, or gut. Other common causes are tuberculosis, streptococcus, or staphylococcus bacteria.

To infect the heart, bacteria must enter the bloodstream somehow. Most commonly this happens through a cut. It can also be caused by intestinal bacteria that get into the blood after a bowel infection. Unlike viral infections, bacteria don’t often cause myocarditis. Instead, bacterial infections more commonly result in endocarditis when bacteria settle on the inner walls of the heart and valves.

Other Causes of a Heart Infection

Viruses and bacteria aren’t the only possible causes of a heart infection. Inflammation can result from any kind of hostile substance in the body, from fungi to parasites to toxins and more. Some cases of myocarditis are even caused by hypersensitivity to certain drugs or insect bites, as well as unhealed heart injuries.

Planning Effective Treatments

To effectively treat the heart infection, doctors must first learn its root cause. The doctor may take a biopsy – a small sample of tissue – and study it under the microscope. If there are immune cells visible, the type of inflammation can help the doctor decide which medicine is best. They may also be able to conduct a PCR test to determine if a bacterial or viral infection is present. If so, the doctor may prescribe antibacterial and antiviral medications. Antibacterial or antiviral medications will fight the cause at its source, while anti-inflammatory medicine prevents the immune system from causing more damage.

“The most important thing to remember, however, is that myocarditis is a major risk for cardiac death,” says Fairweather. No matter the cause of the infection, standard heart failure medications are a necessary part of treatment to help a patient recover. To learn more about heart infections, contact the Myocarditis Foundation today.

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