Endocarditis is a condition in which the endocardium—the membrane that lines the chambers of the heart and heart valves—becomes inflamed, typically as a result of a bacterial or fungal infection.

Endocarditis usually involves one or more of the heart’s four valves, all of which regulate the flow of blood through the heart and to the rest of the body. In people with endocarditis, the valves may become damaged, impairing the movement of blood, which can lead to a number of serious, life-threatening heart issues.

People with bacterial or fungal endocarditis—known collectively as infective endocarditis—typically have flu-like symptoms, including fever, sweats, chills, and fatigue. Other symptoms may also develop, such as tiny red spots on the skin, blood under the fingernails, or blood in the urine. In rare cases, endocarditis can occur without an infection. What’s called “noninfective endocarditis” usually doesn’t cause symptoms, though some people may experience shortness of breath, heart palpitations, and fever.

Endocarditis can affect people of any age, though it’s most common in older adults. It’s a serious condition; if left untreated, endocarditis can lead to heart failure, stroke, heart attack, and even death. Fortunately, effective treatments are available and with early treatment, damage to the heart and valves may be prevented.

“Infective endocarditis can be successfully cured with appropriate diagnosis and treatment,” says Nikhil Seval, MD, an assistant professor in infectious disease at Yale School of Medicine. “Although certain infections will require intravenous antibiotics paired with cardiac surgery to replace the infected valve, in other cases we can achieve a cure through antibiotics alone, increasingly with oral antibiotics to complete treatment.”

Endocarditis is a term that refers to inflammation of the endocardium, the thin inner membrane that covers the heart and heart valves. It’s usually caused by a bacterial infection, though less commonly it can be the result of a fungal infection.

In infective endocarditis, bacteria or fungi enter the bloodstream and circulate throughout the body, including the heart and its four valves. These pathogens may get into the bloodstream in many ways, for instance during surgery or a dental procedure or via use of IV drugs.

In people with a healthy heart and heart valves, these pathogens very rarely infect the endocardium. People with certain cardiac conditions, however, are at increased risk. Among others, these conditions include heart valve disease, congenital heart disease, and having an artificial heart valve.

When the endocardium gets infected, clumps of bacteria or fungi and other substances—proteins and blood cells—form. These clumps, known as vegetations, can break away from the endocardium and travel to other parts of the body. Vegetations can lodge in blood vessels, blocking blood flow to organs such as the heart (causing a heart attack) or brain (causing a stroke).

Endocarditis can also damage the heart valves, causing problems with blood flow and leading to heart failure and other heart problems. Without treatment, endocarditis is a life-threatening condition.

Noninfective endocarditis works in much the same way. The key difference is in the makeup of the vegetations—in noninfective endocarditis, the vegetations that form on the heart valves or on the endocardium are made up of proteins and blood cells (including platelets and fibrin), but they don’t contain bacteria or other microorganisms. The exact cause of noninfective endocarditis isn’t known, but is thought to occur when an area of the endocardium gets damaged, for instance due to certain cancers or congenital heart defects.

There are two general types of infective endocarditis:

• Acute endocarditis, which progresses rapidly, usually over a few days.
• Subacute endocarditis, which progresses gradually, typically over weeks or months.

Doctors usually further classify infective endocarditis in several ways, such as whether the infection is caused by bacteria or fungi (as well as the species of bacteria or fungi) or whether it involves a prosthetic heart valve or a person’s own “native” heart valve.

As mentioned above, in rare cases endocarditis without an infection can occur.

Several factors increase the risk of infective endocarditis, including:

• Heart valve disease
• Congenital heart disease
• Having a prosthetic heart valve or implanted cardiac device
• History of infective endocarditis
• Recent dental work
• Recent surgery
• Central venous catheter (a catheter, or tube, that is inserted into a large, central vein to deliver medications or collect samples)
• Dialysis
• Diabetes
• HIV infection
• Use of IV drugs
• Rheumatic heart disease

Risk factors for noninfective endocarditis include:

• Systemic lupus erythematosus
• Uremia (buildup of waste and toxins in blood)
• Antiphospholipid syndrome (a condition marked by increased formation of blood clots)
• Insertion of catheter in the heart
• Cancer
• Burns
• Tuberculosis
• HIV infection

Symptoms of endocarditis may include:

• Fever
• Chills
• Night sweats
• Fatigue
• Joint and muscle pain
• Loss of appetite
• Shortness of breath
• Weight loss
• Chest pain
• Blood in urine
• Small, red spots on the palms and soles
• Thin lines of blood under the nails
• Painful, reddish bumps on fingers and toes

People with noninfective endocarditis often don’t have any symptoms, though some may have shortness of breath or heart palpitations.

To diagnose endocarditis, your doctor will assess your medical history, perform a physical exam, and run diagnostic tests.

Diagnosis often begins with a review of the patient’s medical history. This means your doctor may ask about your symptoms, when they began, and whether you have any risk factors for endocarditis. He or she will also conduct a physical exam to check for physical signs of endocarditis such as skin changes, a heart murmur, or an enlarged, spleen among others.

To confirm diagnosis, your doctor will need to order additional tests. In most cases, three separate blood draws will be necessary. These blood samples will be analyzed to see whether a bacterial or fungal infection is present, and if so, to identify the type of bacteria or fungus. Additional analyses, such as a complete blood count (CBC) and C-reactive protein, among others, may also be carried out using the blood samples.

A diagnosis of endocarditis also involves an echocardiogram (ECG or EKG), an imaging test that uses ultrasound waves to produce an image of the heart as it beats. Additional imaging tests may also help the doctor make a diagnosis, such as a chest X-ray, a magnetic resonance imaging (MRI) scan, computed tomography (CT) scan, and a positron emission tomography (PET) scan. For patients who have neurological symptoms, a brain MRI may be necessary. 

Treatments for endocarditis may include:

• Antibiotics are used to treat bacterial endocarditis. Doctors will determine the best antibiotic to use depending on the type of bacteria causing the infection and whether patients are allergic to certain antibiotics. Usually, antibiotics are initially given intravenously for several weeks, though patients may also need to take oral antibiotics after completing a course of IV treatment. In all, antibiotic treatment typically lasts 2 to 6 weeks, with the aim of completely eliminating the infection.
• Antifungal medications. These medications may be used to treat endocarditis caused by a fungal infection.
• Blood thinners. Noninfective endocarditis is usually treated with blood thinners to reduce the risk of blood clot formation.
• Surgery. Some patients may need surgery to replace or repair damaged heart valves or to remove implanted devices (e.g., a pacemaker or a cardioverter defibrillator) that are sites of infection. Abscesses—pockets of pus caused by infection—may be drained during surgery.

The outlook for people with endocarditis depends on several factors, including their age, the type of bacteria or fungi that causes the infection, if applicable, and what parts of the heart are affected.

A number of complications may occur in people who have endocarditis. Among others, these include heart failure; fistulas (abnormal connections between blood vessels and chambers of the heart); and abscesses in the brain, near heart valves, or in the spleen or kidney.

Because endocarditis is a life-threatening condition with a risk of serious complications, it’s essential that people who develop symptoms seek treatment right away. Early treatment can stop disease progression and limit damage to the heart and heart valves.

“Here at Yale we utilize a multidisciplinary care team model for endocarditis treatment which includes specialists from cardiothoracic surgery, infectious diseases, cardiology, and other departments and programs to provide personalized management recommendations, particularly for our patients living with addiction who have infectious complications. Collaborative care is increasingly recognized as the best strategy to improve care for this disease.”