Infective Endocarditis: Symptoms, Diagnosis, Vegetations, and Treatment
Assoc. Prof. Sezen Bağlan Uzunget, MD
Cardiologist
What Is Infective Endocarditis?
Infective endocarditis is a serious infection involving the inner lining of the heart, particularly the heart valves.
It is most commonly caused by bacteria and less frequently by fungi.
The infection may affect native heart valves, prosthetic valves, certain congenital heart defects, or intracardiac devices such as pacemaker and defibrillator leads.
Infective endocarditis can be life-threatening and often requires prompt hospital-based diagnosis and treatment.
How Does Infective Endocarditis Develop?
Microorganisms may enter the bloodstream and attach to heart valves or intracardiac prosthetic material.
Infected masses called vegetations may form.
These structures contain microorganisms, fibrin, and platelets.
Vegetations may damage heart valves or release embolic material into the circulation.
Potential sources of bloodstream infection include oral and dental infections, skin infections, intravascular catheters, and other infectious conditions.
Sometimes no clear source is identified.
Which Microorganisms Cause Infective Endocarditis?
Common pathogens include:
- Staphylococcus aureus
- Viridans group streptococci
- Streptococcus gallolyticus
- Enterococcus faecalis
- Coagulase-negative staphylococci
Less common causes include HACEK organisms, other bacteria, and fungi.
Identifying the pathogen is essential for selecting appropriate antimicrobial treatment.
Who Is at Increased Risk?
Risk is higher in certain patients, including those with:
- Previous infective endocarditis
- Prosthetic heart valves
- Prosthetic material used for valve repair
- Certain congenital heart diseases
- Pacemakers or implantable defibrillators
- Injection drug use
- Long-term intravascular catheters
- Hemodialysis
However, endocarditis may also develop in people without previously diagnosed heart disease.
What Are the Symptoms of Infective Endocarditis?
Symptoms vary depending on the organism and clinical course.
Common symptoms include:
- Fever
- Chills
- Night sweats
- Fatigue
- Loss of appetite
- Weight loss
- Muscle and joint pain
- Shortness of breath
- Palpitations
Some infections progress rapidly, while others cause symptoms over several weeks.
Unexplained fever in a patient with a prosthetic valve or previous endocarditis requires prompt medical evaluation.
How Does Endocarditis Damage Heart Valves?
Infection may cause:
- Valve regurgitation
- Valve leaflet perforation
- Perivalvular abscess
- Prosthetic valve dysfunction or dehiscence
- Heart failure
Acute severe aortic or mitral regurgitation can cause rapidly progressive heart failure.
What Is a Vegetation?
A vegetation is an infected mass that may develop on a heart valve or another intracardiac structure.
Echocardiography can help detect vegetations.
Important features include:
- Size
- Mobility
- Location
- Changes over time
- Previous embolic events
However, not every mass seen on echocardiography represents infective endocarditis.
Imaging findings must be interpreted alongside clinical and microbiological evidence.
How Is Infective Endocarditis Diagnosed?
Diagnosis relies on:
- Clinical assessment
- Blood cultures
- Cardiac imaging
Additional imaging and microbiological investigations may be necessary.
1. Blood Cultures
Blood cultures help identify the microorganism causing the infection.
Multiple appropriately collected blood culture sets should generally be obtained before starting antibiotics when feasible.
In critically ill patients, diagnostic sampling and treatment should be performed promptly without unnecessary delay.
Negative blood cultures do not completely exclude endocarditis.
Previous antibiotic treatment or difficult-to-culture organisms may contribute to culture-negative cases.
2. Transthoracic Echocardiography (TTE)
TTE is an important initial imaging method.
It evaluates valves, vegetations, regurgitation, and cardiac function.
3. Transesophageal Echocardiography (TEE)
TEE provides more detailed visualization of cardiac structures.
It is particularly valuable in:
- Suspected prosthetic valve endocarditis
- Evaluation of perivalvular abscesses
- Inconclusive TTE findings
- Suspected intracardiac device infection
- Assessment of complications
Repeat imaging may be necessary when initial findings are negative but clinical suspicion remains high.
4. Cardiac CT and Nuclear Imaging
Selected patients may benefit from cardiac CT, FDG-PET/CT, or labeled white blood cell imaging.
These methods can help assess prosthetic valve infection, device-related infection, and perivalvular complications.
What Are the Duke Criteria?
Updated Duke diagnostic criteria combine clinical, microbiological, and imaging findings.
They help classify cases as definite or possible infective endocarditis.
Positive blood cultures and characteristic imaging findings are important evidence.
However, diagnosis requires interpretation of the entire clinical picture.
What Complications Can Endocarditis Cause?
1. Heart Failure
Severe valve damage may lead to heart failure.
2. Stroke
Embolic material from left-sided vegetations may travel to the brain and cause ischemic stroke.
3. Systemic Embolism
Emboli may affect the kidneys, spleen, and other organs.
4. Septic Pulmonary Embolism
Right-sided endocarditis, particularly involving the tricuspid valve, may cause septic emboli in the lungs.
5. Perivalvular Abscess
Infection may spread beyond the valve into surrounding tissue.
New conduction abnormalities can be an important warning sign, especially in aortic valve endocarditis.
6. Uncontrolled Infection
Persistent bloodstream infection, abscess formation, or resistant pathogens may complicate treatment.
How Is Infective Endocarditis Treated?
Treatment is usually initiated in the hospital.
1. Antibiotic Therapy
Antibiotics are the foundation of treatment.
The regimen depends on:
- Identified microorganism
- Antimicrobial susceptibility
- Native versus prosthetic valve involvement
- Kidney function
- Associated complications
Treatment commonly lasts several weeks.
Many patients require four to six weeks of therapy, although the duration varies.
In selected stable patients, outpatient intravenous or carefully selected oral antibiotic treatment may be considered after an appropriate initial treatment phase and specialist assessment.
2. Cardiac Surgery
Some patients require valve repair or replacement in addition to antimicrobial treatment.
When Is Surgery Necessary?
Surgery is primarily considered for three major reasons.
Heart Failure
Severe valve dysfunction causes clinically significant heart failure.
Uncontrolled Infection
Examples include perivalvular abscess, progressive local infection, or infection that remains uncontrolled despite appropriate treatment.
Prevention of Embolism
Certain large, mobile vegetations or embolic events may support early surgery in appropriately selected patients.
The need for surgery and its timing should be determined by a multidisciplinary team.
Not every vegetation requires surgery, and vegetation size alone is not sufficient to determine treatment.
What Is Prosthetic Valve Endocarditis?
Prosthetic valve endocarditis is an infection involving a mechanical or biological heart valve prosthesis.
It can be more challenging to diagnose and treat than native valve endocarditis.
Potential complications include abscess formation, prosthetic dehiscence, and valve dysfunction.
TEE, cardiac CT, and selected nuclear imaging techniques may be useful.
Can Pacemakers and ICDs Become Infected?
Yes.
Cardiac implantable electronic devices may develop pocket infections, lead infections, or associated intracardiac infection.
In many patients with definite device infection, antibiotic treatment alone is insufficient and complete system removal is required.
Management depends on the extent of infection and clinical status.
Are Antibiotics Necessary Before Dental Procedures?
Not every patient with heart disease requires antibiotics before dental treatment.
Antibiotic prophylaxis is recommended for selected patients at high risk of infective endocarditis undergoing certain dental procedures involving gingival manipulation, the periapical region, or perforation of the oral mucosa.
High-risk groups include patients with:
- Previous infective endocarditis
- Prosthetic heart valves
- Prosthetic material used for valve repair
- Certain congenital heart conditions
Other specific high-risk situations may require individualized assessment.
Mitral valve prolapse, bicuspid aortic valve, or ordinary native valve regurgitation alone does not routinely justify antibiotic prophylaxis before dental procedures.
The choice and timing of antibiotics should follow current guidance and consider drug allergies.
How Can Infective Endocarditis Be Prevented?
Important measures include:
- Good oral hygiene
- Regular dental care
- Prompt treatment of dental and skin infections
- Appropriate intravascular catheter care
- Avoidance of unnecessary invasive vascular procedures
- Antibiotic prophylaxis when indicated
Maintaining good oral health is an important part of prevention.
Can Infective Endocarditis Be Cured?
Many patients can be successfully treated with appropriate antibiotics and surgery when necessary.
Prognosis depends on:
- The causative organism
- The affected valve
- Severity of valve damage
- Presence of heart failure
- Embolic complications
- Associated medical conditions
Clinical and echocardiographic follow-up may be necessary after treatment.
Can Infective Endocarditis Recur?
Yes.
Patients with previous infective endocarditis remain at increased risk of future episodes.
Preventive measures, dental care, and appropriate prophylaxis are therefore important.
When Is Emergency Assessment Necessary?
Urgent evaluation is required for:
- Unexplained fever in a patient with a prosthetic valve or previous endocarditis
- New or worsening shortness of breath
- Sudden speech disturbance or limb weakness
- Syncope
- Severe systemic illness
- Signs of sepsis or shock
Frequently Asked Questions
Does a vegetation on echocardiography always mean endocarditis?
No. Echocardiographic findings must be interpreted with blood cultures and the clinical presentation.
Can endocarditis be treated with antibiotics alone?
Yes, in some patients. Others require surgery because of valve damage, uncontrolled infection, or embolic risk.
Does everyone with endocarditis need valve replacement?
No. Surgery is reserved for patients with appropriate indications.
Can endocarditis cause stroke?
Yes. Emboli from left-sided vegetations may cause ischemic stroke.
Does a pacemaker alone require antibiotics before dental treatment?
No. A pacemaker or ICD alone is not an indication for routine dental endocarditis prophylaxis.
This content is provided for general educational purposes. Infective endocarditis often requires multidisciplinary evaluation involving cardiology, infectious diseases, cardiac surgery, and other specialists when appropriate.