Diagnosis Criteria for Infective Endocarditis
Infective endocarditis refers to an infection of the inner lining of the heart chambers and valves, often involving implanted devices such as pacemaker wires or intracardiac leads. The infection typically results from bacteria entering the bloodstream and attaching to damaged areas of the heart lining. Diagnosing this condition requires a combination of clinical evaluation, laboratory testing, and imaging studies.
Main Diagnostic Criteria
1. Persistent Fever
One of the most common signs of infective endocarditis is prolonged fever. Patients often experience recurrent episodes of high temperature, typically above 39°C (100.4°F), which may not respond well to initial antibiotic treatments. This fever usually lasts for more than two weeks and can be accompanied by chills and night sweats.
2. Blood Culture Results
Blood cultures play a crucial role in confirming the diagnosis. To meet the diagnostic criteria, a patient should have at least two positive blood cultures taken at different times, showing the same causative organism. Alternatively, if multiple blood cultures are performed, at least 75% of them should be positive for the same pathogen. These results help identify the specific bacteria causing the infection and guide appropriate antibiotic therapy.
3. Evidence of Cardiac Involvement
Structural changes in the heart, particularly the valves, are key indicators of endocarditis. This includes the presence of vegetations—abnormal growths on the heart valve leaflets—typically composed of bacteria and blood clots. Additionally, newly developed or worsening heart valve regurgitation can also support the diagnosis. These findings are usually detected through echocardiography, especially transesophageal echocardiography (TEE), which provides a more detailed view of the heart structures.
Supporting Diagnostic Factors
If two of the main criteria are present along with supporting clinical features, the diagnosis can still be considered. These include:
- Underlying heart disease or a history of endocarditis
- Systemic complications such as embolic events or stroke
- Signs of anemia or unexplained fatigue
- Evidence of kidney damage or abnormal renal function
Combining these secondary findings with at least two primary criteria can significantly aid in confirming the diagnosis of infective endocarditis.