Endocarditis

Endocarditis is an infection of the inner lining of the heart (the endocardium) and, most importantly, the heart valves. It occurs when bacteria—or less commonly fungi—enter the bloodstream and attach to damaged or abnormal heart tissue. Once attached, these organisms multiply and form clumps called vegetations, which can damage valves, break off and travel through the bloodstream, or cause widespread infection. Endocarditis is a serious condition that requires prompt diagnosis and treatment with antibiotics or surgery. Early detection greatly improves outcomes, while delayed treatment can lead to life-threatening complications.

Overview

Endocarditis is a life-threatening infection of the endocardium, the smooth inner layer of the heart, and it most often involves the heart valves. It develops when bacteria circulating in the bloodstream stick to the valves or nearby tissue. Healthy valves are usually resistant to infection, but damaged, artificial, or abnormal valves are more vulnerable.

The infection forms vegetations—clusters of bacteria, platelets, and fibrin—that can interfere with normal valve movement. These clumps can break off and travel to other parts of the body, causing strokes, organ damage, or blockages in blood vessels. Without treatment, endocarditis can destroy valves, cause severe heart failure, or spread throughout the body.

Although rare, endocarditis is a medical emergency that requires weeks of intravenous antibiotics and sometimes surgery to repair or replace damaged valves.

Causes

Endocarditis occurs when microorganisms enter the bloodstream and attach to the heart’s inner lining.

• The most common cause is bacteria, especially Staphylococcus, Streptococcus, and Enterococcus species.
• Everyday activities can introduce small amounts of bacteria into the bloodstream—brushing teeth, chewing food, or minor injuries. In most people, the immune system clears these bacteria quickly. But in people with abnormal or damaged valves, these bacteria can latch onto the heart lining and cause infection.
• Dental infections or poor oral hygiene increase the risk because bacteria from the mouth frequently enter the bloodstream. Medical procedures involving the mouth, skin, lungs, or urinary tract can introduce bacteria.
• People with prosthetic (artificial) heart valves, previous endocarditis, congenital heart disease, or certain valve abnormalities have a higher risk. Injection drug use is a major risk factor, as skin bacteria can enter the bloodstream directly.
• Fungal endocarditis is rare but more serious, usually seen in people with weakened immune systems or prolonged IV catheter use.

Symptoms

Endocarditis can develop slowly over weeks (subacute) or rapidly over days (acute), so symptoms vary widely.

• Many people experience a prolonged low-grade fever, chills, or night sweats. Fatigue, weakness, loss of appetite, and unintentional weight loss are common early symptoms.
• Chest pain is not always present, but shortness of breath may develop if valves become severely damaged. Persistent cough or swelling in the legs may occur if heart failure develops.
• Skin changes can provide clues: tiny red or purple spots on the skin or inside the mouth, tender nodules on the fingers or toes (Osler nodes), or painless spots on the palms and soles (Janeway lesions). Dark lines under the nails (splinter hemorrhages) may appear.
• As vegetations break loose, they can cause strokes—leading to sudden weakness, confusion, or difficulty speaking—or block blood flow to organs, causing abdominal pain or limb pain.
• Symptoms vary greatly, making early diagnosis challenging.

Diagnosis

Diagnosis relies on a combination of symptoms, blood cultures, and imaging studies. Because early endocarditis may look like many other illnesses, doctors must maintain a high level of suspicion.

• The most important test is blood cultures, which identify the organism causing the infection. Multiple blood samples are taken to confirm the diagnosis.
• Echocardiography—especially transesophageal echocardiogram (TEE)—is crucial. It provides detailed images of the heart valves and can reveal vegetations, abscesses, or valve destruction. A transthoracic echocardiogram (TTE) is often performed first but may miss small lesions.
• Blood tests often show signs of inflammation, anemia, or kidney involvement. Additional imaging such as CT or MRI may be used if complications are suspected.

Diagnosis is based on a combination of clinical findings and the Duke criteria, which consider blood culture results, imaging findings, and physical signs.

Treatment

Treatment begins immediately once endocarditis is suspected. Therapy typically includes weeks of intravenous antibiotics, chosen based on the specific bacteria found in blood cultures. Early, targeted antibiotic therapy is essential for preventing valve destruction and other complications.

People with prosthetic valves, fungal infections, or severe valve damage often require more aggressive treatment. Surgery may be needed to remove infected tissue, repair a damaged valve, or replace a valve destroyed by infection.

Supportive care includes monitoring for heart failure, arrhythmias, stroke, or embolic events. Treating any underlying condition—such as dental disease or skin infection—is important to prevent recurrence.

Injection drug use–related cases require addiction treatment and harm-reduction strategies to lower the risk of future infections.

What Happens If Left Untreated

Untreated endocarditis is almost always fatal. Vegetations continue growing, destroying valves and causing severe heart failure. Fragments can break loose and travel to the brain, lungs, or other organs, causing strokes, organ failure, or life-threatening blockages.

Bacteria can spread to the bloodstream, causing sepsis—a severe, body-wide infection. Without antibiotics and sometimes surgery, the infection overwhelms the body and leads to rapid deterioration.

Even mild-appearing cases can progress silently, making early diagnosis and treatment critical.

What to Watch For

Persistent fever, chills, unexplained fatigue, or weight loss should prompt medical evaluation, especially in individuals with known heart valve disease or risk factors. New shortness of breath, swelling, sudden neurological symptoms (difficulty speaking, weakness, or confusion), or dark streaks under the nails should also raise concern.

People with artificial valves or previous endocarditis should report any signs of infection promptly, including dental infections, skin infections, or fever after medical procedures.

Living with Endocarditis

Recovery requires patience and close follow-up. Completing the full course of IV antibiotics—often 4 to 6 weeks—is essential. Many people receive these treatments at home with specialized nursing support.

Regular follow-up includes repeat blood tests and imaging to ensure the infection is controlled and valves are functioning properly. People with valve replacements require lifelong monitoring.

Preventing recurrence is a key part of long-term care. Maintaining excellent oral hygiene, treating dental issues promptly, and informing healthcare providers about valve disease before procedures are essential steps. Some high-risk individuals may need preventive antibiotics before certain dental procedures.

Lifestyle changes—such as quitting smoking, controlling chronic medical conditions, and addressing substance use—greatly reduce the risk of another infection.

With appropriate treatment, many people recover well, but ongoing surveillance is critical.

Key Points

• Endocarditis is a serious infection of the heart’s inner lining and valves, usually caused by bacteria in the bloodstream.
• It forms vegetations that can damage valves and travel to other organs, causing severe complications.
• Diagnosis relies on blood cultures, echocardiography (especially TEE), and clinical findings.
• Treatment requires weeks of IV antibiotics and, in some cases, surgery to repair or replace damaged valves.
• Without treatment, endocarditis is life-threatening. Early detection and complete treatment greatly improve outcomes.
• Maintaining good oral hygiene, treating infections promptly, and following preventive guidelines are essential for reducing recurrence risk.

Reference: Endocarditis