How Is Endocarditis Diagnosed?
Endocarditis is an infectious disease; as such, diagnosis depends on both the microbiology involved and the damage that can result from it.
Diagnosis Is Based On
- Clinical presentation/signs and symptoms
- Three sets of blood cultures
- Cardiac ultrasonography
- Fever: Any patient with cardiac risk factors (structural abnormalities or valve disease) or IV drug abuse, indwelling IV lines, immunosuppression, or recent dental/surgical procedure who presents with fever should be considered for a diagnosis of endocarditis–at least to rule it out.
At least three sets of blood cultures are obtained to decrease the chance of a false negative result. If a patient is clinically unstable, empiric treatment (treatment based on observation and judgment in lieu of positive cultures) may need to begin even before the results of the cultures are ready.
Follow-up cultures are obtained after 2-3 days of antibiotic treatment, and then every 2-3 days thereafter until the bacteremia has cleared.
There are conditions that mimic infectious endocarditis but which result in negative cultures: antiphospholipid syndrome, non-infectious intracardiac vegetations from acute rheumatic fever, atrial myxoma, non-infectious lesions of the heart such as malignancy, lupus, and nonbacterial thrombotic endocarditis from a state of hypercoagulation.
Echocardiography (TTE and TEE)
A transthoracic (transducer over chest) cardiac echogram (TTE) is performed initially and if there is suspicion of infectious endocarditis, difficulty in imaging, or high risk factors for infective endocarditis, a transesophageal echocardiogram is the next step for better visualization and diagnostic accuracy. The findings of the TTE or the TTE/TEE sequence are compared with the microbiology garnered from the blood cultures.
Positive findings in echocardiography include
- pathologic lesions: “vegetations,” masses of platelets, fibrin, bacterial colonies, inflammatory cells, or–later–fibrosis and calcification
- intracardiac abscess
Echocardiography is also useful, in the absence of ultrasonic evidence of vegetations, of steering diagnostics away from endocarditis in pursuit of other conditions that may mimic its signs and symptoms, e.g., catheter infection, infections in implantable cardiac devices, prosthetic joint infection, osteomyelitis and other tissue infection, meningitis, pneumonia, or systemic sepsis.
Other tests can be helpful to discern tissue extension of disease and vascular involvement: cardiac MRI, CT angiography.