Endocarditis

Overview

Endocarditis is an inflammation of the endocardium — the thin inner lining of the heart chambers and valves. In the vast majority of cases, the condition is caused by bacteria that enter the bloodstream and settle on the heart valves; less commonly, fungi are responsible. Once attached, these microorganisms multiply and form infected deposits called vegetations. Over time, vegetations can destroy valve tissue, impair valve function, and set the stage for life-threatening complications.

Also known as infective endocarditis, the condition carries a significantly elevated risk in individuals with previously damaged or prosthetic (artificial) heart valves, congenital heart disease, or a weakened immune system. Intravenous drug use is another major risk factor. However, endocarditis can also develop in people with entirely healthy heart valves.

The disease presents in two distinct patterns. Acute endocarditis is caused by aggressive bacteria — typically Staphylococcus aureus — progresses rapidly, and can cause a life-threatening illness within days to weeks. Subacute endocarditis is caused by less virulent organisms, evolves insidiously over weeks or months, and its symptoms — low-grade fever, fatigue, aching — are easily mistaken for influenza or chronic fatigue.

Endocarditis is a serious condition in which early diagnosis and appropriate antibiotic therapy are genuinely life-saving. Left untreated or diagnosed late, it can result in heart failure, stroke, and death. Even with intensive in-hospital treatment, mortality remains approximately 15–30 percent — a stark reminder of how seriously this disease must be taken.

Symptoms

The symptoms of endocarditis vary depending on the type and speed of progression. Acute endocarditis presents suddenly and severely; subacute endocarditis develops insidiously over weeks.

Endocarditis symptoms include the following:

• Fever and chills. This is the most common symptom. Fever typically exceeds 38°C and may spike and fall at certain times of day. Chills, drenching sweats, and profound malaise accompany it. In subacute forms, the fever may be low-grade and persist for weeks.
• Heart murmur. Vegetations on the valve leaflets disturb blood flow, producing a new murmur or altering a pre-existing one. A new or changed heart murmur detected on examination is a critically important sign of endocarditis.
• Fatigue and malaise. Marked, unexplained fatigue and generalized weakness are common. Daily activities may become difficult to sustain.
• Muscle and joint aches. Myalgias and arthralgias affecting various parts of the body are frequently reported and can be easily confused with influenza.
• Night sweats. Drenching sweats during the night — soaking clothing and bedding — are particularly characteristic of the subacute form.
• Shortness of breath. When valve destruction impairs the heart's pumping function, breathlessness develops. Initially noticed only with exertion, it may progress to occur at rest as the disease advances.
• Loss of appetite and weight loss. Chronic infection and systemic inflammation suppress appetite; prolonged illness leads to unintentional weight loss.
• Characteristic skin and eye findings. Several findings are particularly associated with endocarditis. Petechiae — tiny red or purple pinpoint hemorrhages — appear on the skin, inside the mouth, or on the whites of the eyes. Osler nodes are painful, reddish nodules on the fingertips or toes. Janeway lesions are painless red macules on the palms or soles. Roth spots are retinal hemorrhages visible on fundoscopic examination.
• Changes in urine color. Emboli or immune complex deposition in the kidneys can cause blood in the urine (hematuria), making it appear dark or reddish.

Symptoms can be so insidious that a person may believe for weeks that they have influenza or chronic fatigue. For this reason, unexplained prolonged fever in anyone with cardiac risk factors should always be taken seriously and investigated promptly.

When to See a Doctor

Endocarditis has the potential to progress rapidly. Medical evaluation should not be delayed once symptoms appear.

Schedule urgent medical evaluation if:

• You have had an unexplained fever lasting more than a few days — especially if you have a heart condition or a prosthetic valve
• You have fever accompanied by shortness of breath, chest pain, or palpitations
• You notice painful nodules on your fingertips or toes
• You observe small red pinpoint spots on your skin, inside your mouth, or on the whites of your eyes
• You have recently had a dental procedure, surgery, or other invasive procedure and subsequently developed fever
• You use intravenous drugs and are experiencing fever and malaise
• You have previously had endocarditis and similar symptoms have recurred

Call emergency services immediately if you experience:

• Sudden stroke symptoms (facial drooping, arm weakness, speech difficulty)
• Sudden severe chest pain or inability to breathe
• Loss of consciousness or sudden confusion
• A limb that becomes suddenly cold, discolored, and painful

Causes

The overwhelming majority of endocarditis cases are bacterial in origin; fungal cases are less common but tend to follow a more severe course.

Causes of endocarditis include the following:

• Streptococci. The viridans group streptococci are the most common cause of subacute endocarditis. Naturally present in the mouth, these bacteria can enter the bloodstream during dental procedures. They adhere readily to previously damaged valve surfaces and form vegetations.
• Staphylococci. Staphylococcus aureus is the most common cause of acute endocarditis and follows an aggressive course. It can enter the bloodstream via skin infections, intravenous catheters, surgical wounds, or intravenous drug use. Uniquely, it is capable of infecting previously healthy heart valves. Methicillin-resistant S. aureus (MRSA) substantially complicates treatment.
• Enterococci. Part of the intestinal and urinary flora, enterococci can cause endocarditis — particularly in older patients and following urinary tract procedures.
• HACEK group organisms. This group — comprising Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella species — are less common causes of subacute endocarditis. They are found in the oral flora.
• Fungi. Candida and Aspergillus species cause endocarditis primarily in immunocompromised patients, those with long-term central venous catheters, and intravenous drug users. Fungal endocarditis is extremely difficult to treat and almost always requires surgical intervention.
• Portals of entry. Microorganisms gain access to the bloodstream through various routes: dental procedures, skin infections, urinary tract infections, intravenous drug use, indwelling catheters or pacemaker leads, and surgical interventions are among the most important.

Risk Factors

Several factors are associated with an increased risk of developing endocarditis:

• Prosthetic heart valves. This group carries the highest risk. Artificial valve surfaces provide a far more favorable substrate for bacterial adhesion than native valves. Prosthetic valve endocarditis is among the most difficult forms to diagnose and treat.
• Prior endocarditis. Individuals who have had endocarditis once face a substantially elevated risk of recurrence. Residual valve damage from previous infection creates vulnerable sites for new bacterial seeding.
• Congenital heart disease. Unrepaired or partially repaired congenital cardiac defects generate abnormal blood flow patterns that render valves more susceptible to infection.
• Rheumatic heart disease. Rheumatic fever in childhood can leave lasting damage on the valve leaflets. These scarred valves represent a significant endocarditis risk.
• Intravenous drug use. People who inject drugs introduce high concentrations of bacteria into the bloodstream via non-sterile needles and solutions. This group has a particularly high incidence of right-sided endocarditis involving the tricuspid valve.
• Indwelling vascular catheters and implanted devices. Permanent pacemaker and defibrillator leads, as well as long-term central venous catheters, provide both a portal of entry and a surface for bacterial colonization.
• Immunosuppression. HIV infection, post-transplant immunosuppressive therapy, and conditions such as diabetes increase susceptibility to endocarditis.
• Advanced age. Degenerative valve calcification in older individuals facilitates bacterial adhesion. This population also undergoes more invasive procedures, further elevating risk.

Diagnosis

Endocarditis is diagnosed through a systematic approach combining clinical assessment, blood cultures, and echocardiography — formalized in the widely used Duke criteria.

Diagnostic methods include the following:

• Blood cultures. These are the cornerstone of diagnosis. At least three sets of blood cultures drawn from different sites and at different times identify the causative organism and determine antibiotic susceptibility. It is critical that cultures are obtained before antibiotics are started; early antibiotic administration can sterilize the blood and render cultures falsely negative.
• Echocardiography. This is used to visualize vegetations on the valves, assess valve damage, and detect complications such as abscesses. Transthoracic echocardiography (TTE) — performed from outside the chest — is the initial modality. When image quality is limited or more detail is required, transesophageal echocardiography (TEE) is performed by placing an ultrasound probe in the esophagus. TEE provides significantly superior imaging and is much more sensitive for detecting small vegetations and perivalvular abscesses.
• Complete blood count and inflammatory markers. An elevated white blood cell count, high CRP, and raised erythrocyte sedimentation rate reflect active infection and inflammation. Anemia is a common finding in subacute endocarditis.
• Renal function tests and urinalysis. These assess kidney involvement. The presence of red blood cells and protein in the urine may indicate renal damage from emboli or immune complex deposition (glomerulonephritis).
• Imaging studies. Brain MRI or CT is used to evaluate for embolic stroke or cerebral abscess. Thoracic and abdominal CT can identify septic embolic foci and other organ involvement. PET-CT may be useful in diagnostically challenging cases to detect occult infection sites.
• Duke criteria. This standardized diagnostic framework classifies cases based on major criteria (positive blood cultures and echocardiographic evidence of endocarditis) and minor criteria (fever, predisposing conditions, vascular phenomena, and immunologic findings). Based on the combination of criteria met, the diagnosis is classified as definite, possible, or rejected.

Treatment

The primary goals of endocarditis treatment are to completely eradicate the infection and minimize valve damage. Treatment is always conducted in a hospital setting and typically requires a prolonged course of antibiotics.

Treatment options include the following:

• Prolonged intravenous antibiotic therapy. This is the foundation of treatment. The antibiotic regimen is selected based on the causative organism and its susceptibility profile and is administered intravenously. Treatment duration is typically 4–6 weeks; prosthetic valve endocarditis and complicated cases may require longer courses. Full adherence to the prescribed regimen is essential — premature discontinuation leads to relapse and promotes antibiotic resistance.
• Fever and pain management. Antipyretics and analgesics provide symptomatic relief. Their use is balanced carefully, as complete suppression of fever can obscure the assessment of treatment response.
• Surgical treatment. Approximately 40–50 percent of endocarditis cases require surgical intervention. Indications include infection that does not respond to antibiotics, severe valve damage causing heart failure, large or enlarging vegetations posing high embolic risk, perivalvular abscess, and fungal endocarditis. Surgery involves removal of infected tissue and vegetations, followed by valve repair or replacement with a biological or mechanical prosthesis.
• Fungal endocarditis treatment. Antifungal agents such as amphotericin B and echinocandins are used, but medical therapy alone is almost never sufficient — surgical valve replacement is nearly always required. Outcomes are considerably worse than for bacterial endocarditis.
• Management of complications. Heart failure is treated with diuretics and other cardiac medications. Embolic stroke requires co-management with a neurology team. Renal involvement warrants nephrology consultation.
• Post-discharge care. In selected patients, the remainder of the intravenous antibiotic course may be completed at home with appropriate monitoring. Regular blood tests and antibiotic level measurements are performed. Close cardiology follow-up is mandatory in the first months after discharge.

Complications

If not treated early and appropriately, endocarditis can give rise to numerous serious complications:

• Heart failure. This is the most common and most important complication. Destruction or perforation of the valve leaflets causes acute valvular regurgitation; when the heart cannot compensate, acute heart failure ensues. The majority of emergency surgical cases are driven by heart failure.
• Embolic events. Fragments breaking off from valve vegetations travel through the bloodstream to distant organs. Migration to the brain causes ischemic stroke; to the coronary arteries, heart attack; to the kidneys, renal infarction; to the spleen, splenic infarction; and to the leg arteries, acute limb ischemia. Embolic events occur in 20–40 percent of cases.
• Perivalvular abscess. Infection spreading beyond the valve into adjacent cardiac tissue forms an abscess. This can disrupt the cardiac conduction system, leading to serious arrhythmias and complete heart block, and almost always requires surgical drainage.
• Neurological complications. Beyond embolic stroke, brain abscess, meningitis, toxic encephalopathy, and intracranial hemorrhage may occur. Neurological complications substantially worsen both mortality and long-term quality of life.
• Renal failure. Septic emboli, immune complex deposition (glomerulonephritis), and antibiotic nephrotoxicity can all impair kidney function. Acute kidney injury in severe cases may require dialysis.
• Relapse and persistent infection. Premature discontinuation of antibiotics, inadequate treatment duration, or resistant organisms can allow the infection to persist and relapse. The risk of recurrent endocarditis remains significantly elevated after a first episode.

Living with Endocarditis

Endocarditis treatment is a prolonged and demanding process. However, with early diagnosis, appropriate therapy, and careful follow-up, the great majority of patients achieve full recovery and return to normal life.

During Treatment

During the hospital phase of intravenous antibiotic therapy, regular blood tests, repeat echocardiography, and fever monitoring are conducted. This phase may last 4–6 weeks; patience and strict adherence to treatment are essential. After discharge, some patients transition to oral antibiotics or home intravenous therapy — in either case, follow-up appointments must not be missed.

Oral and Dental Hygiene

Good oral hygiene plays a key role in preventing endocarditis. Brush your teeth at least twice daily and use dental floss regularly. Prevent gum disease by attending dental check-ups every six months. If you are in a high-risk group — prosthetic valve, prior endocarditis, or certain congenital heart conditions — discuss antibiotic prophylaxis before dental procedures with your cardiologist.

Antibiotic Prophylaxis

In high-risk patients, antibiotic prophylaxis is administered before certain invasive procedures — particularly tooth extractions and gingival work. Ask your cardiologist exactly which procedures require prophylaxis. Always inform any treating clinician about your cardiac history, and consider carrying a medical alert card that documents your condition.

Manage Your Risk Factors

If you use intravenous drugs, seek addiction treatment — doing so reduces your risk of endocarditis along with a wide range of other serious health consequences. Do not neglect skin infections or open wounds; have them treated promptly. If you have known valve disease, maintain regular cardiology follow-up.

Ongoing Follow-up

Continue regular cardiology check-ups even after treatment is complete. More frequent monitoring is needed in the first year; thereafter, annual echocardiography is generally recommended. If symptoms such as fever, fatigue, or breathlessness recur, seek medical attention without delay.

Preparing for Your Appointment

Coming prepared to your appointment helps ensure an accurate diagnosis and prompt initiation of treatment.

What you can do:

• Note when the fever began and how it has evolved
• Mention any recent dental procedures, surgery, or other invasive interventions
• Inform your doctor of any known heart disease, prosthetic valves, or congenital cardiac defects
• List all current medications and supplements
• Describe any skin findings you have noticed — such as painful nodules on fingertips or tiny red spots
• Report any family history of heart disease or endocarditis
• Write down your questions in advance

Questions you may wish to ask your doctor:

• Is the endocarditis diagnosis confirmed, or are other conditions being considered?
• Which bacteria or fungus is responsible?
• How long will treatment last?
• Is surgery likely to be needed?
• Can part of the treatment be completed at home?
• What can I do to prevent endocarditis from recurring?
• Will I need antibiotics before future dental or surgical procedures?
• When can I expect to return to normal activities and work?

Questions your doctor may ask:

• When did the fever start, and how high has it been?
• Have you had any dental work, surgery, or invasive procedures recently?
• Do you have known heart disease or a prosthetic valve?
• Do you use intravenous drugs?
• Are you experiencing shortness of breath, chest pain, or palpitations?
• Have you noticed painful nodules on your fingers or red spots on your skin?
• Have you seen blood in your urine recently?
• Have you had endocarditis before?