Symptoms and Diagnosis of Infective Endocarditis
Fever is the most common symptom of infective endocarditis (IE), occurring in up to 90% of patients, often accompanied by systemic symptoms such as chills, poor appetite, and weight loss. 1
Clinical Presentation
Common Symptoms
- Fever (up to 90% of cases), often with chills, poor appetite, and weight loss 1
- Heart murmurs (found in up to 85% of patients) 1
- Embolic phenomena (present in up to 25% of patients at diagnosis) 1
- Dyspnea (reported in over 50% of patients) 2
- Vascular and immunological phenomena including splinter hemorrhages, Roth spots, and glomerulonephritis 1
Clinical Scenarios Requiring High Suspicion for IE
- New regurgitant heart murmur 1
- Embolic events of unknown origin 1
- Sepsis of unknown origin, especially if associated with typical IE causative organisms 1
- Fever in patients with prosthetic heart valves, pacemakers, or implantable defibrillators 1
- Fever in patients with previous history of IE or valvular/congenital heart disease 1
- Fever in immunocompromised patients or intravenous drug users 1
Atypical Presentations
- Elderly or immunocompromised patients may not present with fever 1
- Subacute or chronic disease may present with low-grade fever and non-specific symptoms 1
- Patients may initially present to various specialists with symptoms mimicking chronic infection, rheumatological, neurological, autoimmune diseases, or malignancy 1
Physical Examination Findings
Cardiac Findings
- Heart murmurs (in up to 85% of cases) 1
- Signs of congestive heart failure 1
- New conduction disturbances 1
Peripheral Manifestations
- Embolic phenomena to brain, lung, or spleen (occur in 30% of patients) 1
- Classic peripheral stigmata (increasingly uncommon in developed countries) 1:
Diagnostic Approach
Laboratory Tests
- Blood cultures (positive in approximately 45-50% of cases) 2, 3
- Elevated inflammatory markers (C-reactive protein, erythrocyte sedimentation rate) 1
- Leukocytosis 1
- Anemia 1
- Microscopic hematuria 1
Imaging
Echocardiography is the cornerstone of diagnosis 1:
- Transthoracic echocardiography (TTE) is recommended as first-line imaging 1
- Transesophageal echocardiography (TOE/TEE) should be performed in patients with high clinical suspicion and normal TTE 1
- TEE has better sensitivity and specificity, particularly for diagnosis of abscesses and measurement of vegetation size 1
- Repeat echocardiography within 7-10 days is recommended if initial examination is negative but clinical suspicion remains high 1
Advanced imaging modalities may be necessary in certain cases 1:
Diagnostic Criteria
- Modified Duke criteria are the accepted diagnostic aid for establishing IE diagnosis 3
- Definitive diagnosis often requires integration of clinical, microbiological, and imaging findings 1
Common Pitfalls and Caveats
- Fever may be absent in elderly patients, after antibiotic pre-treatment, in immunocompromised patients, or in IE involving less virulent organisms 1
- Negative blood cultures do not rule out IE, especially in patients who received prior antibiotics 2
- A negative echocardiogram (even TEE) does not rule out IE, particularly in early disease 1
- Delay in diagnosis is common due to non-specific symptoms and varied presentations 1
- Early involvement of a multidisciplinary team including cardiologist and infectious disease specialist is highly recommended for suspected cases 1
- In patients with Staphylococcus aureus bacteremia, echocardiography is essential due to the high frequency of IE in this setting 1
High-Risk Patient Groups
- Patients with prosthetic valves or intracardiac devices 1
- Patients with pre-existing valvular or congenital heart disease 1
- Intravenous drug users 2
- Elderly patients with degenerative valve disease 4
- Patients with frequent healthcare contact (at risk for healthcare-associated IE) 4
Early recognition of symptoms and prompt diagnosis are critical, as IE carries a high mortality rate (approximately 30% at 1 year) even with optimal treatment 5.