Infective Endocarditis: Symptoms, Types, Causes and Treatment

Infective endocarditis (IE) is a life-threatening infection of the heart's inner lining and valves. Once considered a rare disease, it has become an increasingly important health issue worldwide. Modern medicine has improved diagnosis and treatment, but IE remains difficult to manage, with a significant risk of complications and mortality. Understanding its symptoms, types, causes, and current treatment strategies is crucial for early recognition and effective intervention.

Symptoms of Infective Endocarditis

Recognizing the symptoms of infective endocarditis can be challenging, as they often mimic other illnesses and may vary widely between patients. Early detection is key to improving outcomes, but the disease can present acutely or develop slowly over weeks. Some symptoms are classic and well-known, while others are subtle or uncommon, especially in certain populations like children or the elderly.

Symptom	Description	Frequency/Note	Source(s)
Fever	Most common symptom	Up to 90% of cases	2 3 5 8 12
Heart murmur	New or changing	Common	3 8 12
Neurological	Stroke, TIA, confusion, seizures	29% of cases	1 6 8
Embolic events	Stroke, organ infarction, skin signs	25-45%	6 8 14
Classic signs	Osler’s nodes, Janeway lesions	Rare (esp. in children)	3 5 8
Fatigue	General malaise/weakness	Very common	2 5 12

Table 1: Key Symptoms

Common Clinical Features

Fever is the most consistent and prominent symptom of IE, reported in up to 90% of cases. However, it may be absent in elderly patients or those already on antibiotics before diagnosis. Fatigue, malaise, and unexplained weight loss are also frequent, but non-specific, making diagnosis difficult in the early stages 2 3 5 12.

A new or changing heart murmur is a classic sign, especially if the patient has no prior history of heart disease. However, not all patients will have murmurs at presentation, particularly early in the disease or with right-sided involvement 3 8 12.

Neurological and Embolic Complications

Neurological complications occur in up to 29% of patients, ranging from strokes and transient ischemic attacks (TIAs) to seizures, visual loss, and encephalopathy. These complications are often the first manifestation of IE and can result from septic emboli traveling to the brain. Other embolic events may affect the lungs, kidneys, spleen, or skin, manifesting as infarcts or characteristic lesions 1 6 8 14.

Classic Peripheral Signs

Classic signs such as Osler’s nodes (tender finger/toe nodules), Janeway lesions (painless palm/sole spots), Roth spots (retinal hemorrhages), and splinter hemorrhages (under the nails) are historically linked to IE but are now rare, especially in children and in the modern era of earlier diagnosis 3 5 8.

Summary

• Symptoms can be acute or subacute, with fever and fatigue most common
• Neurological and embolic complications are frequent and often severe
• Classic peripheral signs are now rare but remain diagnostic clues
• Diagnosis relies on a combination of clinical suspicion, blood cultures, and echocardiography

Types of Infective Endocarditis

Infective endocarditis is not a single disease but a group of syndromes, classified by the underlying heart substrate, causative agent, or clinical setting. Understanding the types aids in diagnosis and guides management.

Type	Description	Key Features	Source(s)
Native Valve (NVE)	Involves natural heart valves	Most common (~73%)	6 8 12
Prosthetic Valve (PVE)	Infection of artificial valves	More acute, higher mortality	2 6 12
Device-related	Pacemaker/ICD/catheter involvement	Increasingly seen	6 8 12
Right-sided	Affects tricuspid/pulmonary valves	Often IVDU, pulmonary emboli	5 8 12
Healthcare-associated	Linked to medical interventions	Nosocomial, elderly, devices	5 8 12

Table 2: Main Types of Infective Endocarditis

Native Valve Endocarditis (NVE)

NVE is the most prevalent form, accounting for about 73% of cases. Any native valve can be affected, but the mitral and aortic valves are most commonly involved. The disease can be community-acquired or, increasingly, healthcare-associated due to invasive procedures 6 8 12.

Prosthetic Valve Endocarditis (PVE)

PVE refers to infection of an artificial heart valve. It can be classified as early-onset (within 1 year of surgery) or late-onset. PVE tends to be more aggressive, with higher mortality and more frequent complications such as abscess formation or valve dehiscence 2 6 12.

Device-Related Endocarditis

With the rise of cardiac implantable devices (pacemakers, ICDs), device-related IE has become more common. It can affect the device leads, surrounding tissue, or even the tricuspid valve. Outcomes are variable and often require device removal 6 8 12.

Right-sided Endocarditis

Right-sided IE primarily affects the tricuspid valve, often in people who inject drugs (IVDU). It may present with respiratory symptoms due to septic pulmonary emboli. Prognosis is generally better than left-sided IE, but recurrence is common in IVDU 5 8 12.

Healthcare-Associated Endocarditis

This form is linked to hospitalization, invasive procedures, or indwelling catheters. It is more frequent in the elderly and in patients with multiple comorbidities. Staphylococci are often the causative organisms 5 8 12.

Pediatric Endocarditis

Children present differently from adults. Classic peripheral signs are rare, and suspicion should be high in any febrile child with a new murmur, especially with underlying heart defects 3.

Causes of Infective Endocarditis

The cause of infective endocarditis is always an infectious microbe, but the range of possible organisms is broad and evolving. The epidemiology of causative agents has shifted with changes in healthcare, patient population, and medical technology.

Causative Agent	Frequency/Type	Special Notes	Source(s)
Staphylococcus aureus	Leading cause	Healthcare-associated, acute	5 6 9 12
Streptococci (Viridans)	2nd most common	Subacute, dental link	6 9 12
Enterococcus spp.	Common, elderly	GI/GU procedures	6 9 12
Coagulase-neg Staph	Device/PVE	Often resistant	6 9 12
HACEK organisms	Rare (1-3%)	Oral flora, slow-growing	4 6 7 11
Fungi	Uncommon, severe	Prosthetic valves, immunosupp.	4 6 12
Gram-negative bacilli	Uncommon	Healthcare/IVDU	10 4 6

Table 3: Major Causative Agents

Staphylococcus aureus

Now the most common cause of IE worldwide, S. aureus is especially prevalent in healthcare-associated cases, people with indwelling devices, and intravenous drug users. It often causes an acute, aggressive infection with high risk of complications 5 6 9 12.

Streptococci

Viridans group streptococci (VGS) are classic causes of subacute IE, especially after dental procedures or in those with underlying heart disease. S. bovis is associated with colorectal pathology 6 9 12.

Enterococci

Enterococcus species, often originating from the gastrointestinal or genitourinary tract, are increasingly common, particularly in elderly patients or those undergoing invasive procedures 6 9 12.

Coagulase-negative Staphylococci

These bacteria are frequent in prosthetic valve and device-associated IE. They are notable for antibiotic resistance and can cause subacute or chronic infections 6 9 12.

HACEK Organisms

HACEK bacteria (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) are rare, slow-growing, and part of the normal oral flora. They account for 1-3% of cases, often present subacutely, and commonly affect prosthetic valves. Their detection may require special laboratory techniques. Mortality is generally lower than with S. aureus 4 6 7 11.

Fungal and Gram-negative Endocarditis

Fungal IE is rare but devastating, often involving prosthetic valves and immunocompromised patients. Gram-negative bacilli are also uncommon causes but are seen in healthcare settings and in people who inject drugs 4 10 6 12.

Special Considerations

• Fastidious organisms (e.g., Coxiella burnetii, Brucella, Chlamydia) require high suspicion and specific diagnostics 4.
• Approximately 10-25% of cases are blood-culture negative, often due to prior antibiotics or fastidious organisms 6 9.

Treatment of Infective Endocarditis

Managing infective endocarditis is a complex, multidisciplinary task. Timely diagnosis and appropriate therapy are crucial, as delays increase the risk of complications and death. Treatment is tailored based on the causative organism, valve type, and patient characteristics.

Treatment	Description	Key Considerations	Source(s)
Antibiotics	IV, 4-6 weeks (most cases)	Pathogen-guided, high-dose	3 8 12 16
Surgery	For complications or failure	Valve dysfunction, abscess	8 12 14
Oral switch	Selected stable cases	After initial IV therapy	13 16
Outpatient (OPAT)	IV therapy at home	Safe in select patients	15 16
Multidisciplinary	Cardio, infectious, surgical teams	Reduces complications	8 12 14

Table 4: Main Treatment Approaches

Antimicrobial Therapy

• Initial therapy is always intravenous (IV), high-dose, and prolonged (4-6 weeks), tailored to the identified organism and susceptibility. For native valve IE, 4 weeks is typical; prosthetic valve IE often requires 6 weeks 3 8 12 16.
• Empiric therapy starts before pathogen identification in acutely ill or unstable patients, targeting staphylococci, streptococci, and enterococci 16.
• Specific regimens: For methicillin-susceptible S. aureus, anti-staphylococcal penicillins (or cefazolin) are standard; vancomycin or daptomycin for MRSA. For PVE due to staphylococci, add gentamicin and rifampin 16.

Oral Switch and Outpatient Therapy

• Recent evidence supports switching to oral antibiotics in stable patients with left-sided IE after initial IV therapy, without compromising efficacy 13 16.
• Outpatient parenteral antibiotic therapy (OPAT) is safe and effective for selected patients, improving quality of life and reducing hospital stays 15 16.

Surgery

Surgical intervention is needed in up to half of all cases, especially for:

• Severe valve dysfunction causing heart failure
• Uncontrolled infection (abscess, persistent bacteremia)
• Prevention of embolic events (large vegetations)
• Prosthetic valve dehiscence or device infection

Early surgery, in specialized centers, can improve outcomes 8 12 14.

Multidisciplinary Care

Optimal management requires a team approach: infectious disease, cardiology, and cardiac surgery specialists collaborate to reduce complications and guide therapy 8 12 14.

Duration and Follow-up

• Duration: 4 weeks for most native valve IE, 6 weeks for prosthetic valve or complicated cases 3 8 16.
• Careful follow-up after treatment is essential to detect relapse, monitor for complications, and manage long-term sequelae 14.

Prevention

• Antibiotic prophylaxis for dental and invasive procedures is now limited to high-risk patients (e.g., prosthetic valves, previous IE) in most guidelines 3 5 12.
• Education on symptom recognition and prompt medical attention is vital for at-risk individuals 3.

Conclusion

Infective endocarditis is a complex, potentially fatal disease requiring prompt recognition and specialized care. Its symptoms can be subtle or dramatic, and the types, causes, and treatments are diverse and evolving.

Key Takeaways:

• Symptoms include fever, fatigue, heart murmur, and sometimes neurological or embolic events; classic signs are now rare.
• Types include native valve, prosthetic valve, device-related, right-sided, and healthcare-associated endocarditis.
• Causes have shifted, with Staphylococcus aureus now most common, followed by streptococci, enterococci, and rare organisms like HACEK and fungi.
• Treatment relies on early, targeted antibiotics (usually IV for 4-6 weeks), with surgery often needed for complications; oral and outpatient regimens are emerging options in selected cases.
• Multidisciplinary care and patient education are essential for optimal outcomes.

Early suspicion, rapid diagnosis, and individualized, expert management remain the most effective strategies for tackling the ongoing challenge of infective endocarditis.