Infective Endocarditis
Mohammed K. Saghir
Sudeshna Banerjee
Daniel H. Cooper
High-Yield Findings
The clinical presentation should always be considered when interpreting the description of valvular and annular masses on echocardiography.
When the clinical suspicion for endocarditis is high, a TEE is the test of choice.
Concurrent mitral and aortic valve infection is common as they are in direct continuity separated only by a fibrous band of tissue. Therefore examine the aortic root carefully for abscess.
Vegetations often have an echodensity similar to tissue, demonstrate independent movement, and have a predilection for the leading edge and lower pressure side of native valve leaflets.
It is uncommon not to have associated valvular regurgitation in the presence of “vegetations.” Consider other possible causes of valvular masses in this situation.
Endocarditis involving native valves often arises from the leaflets whereas endocarditis of prosthetic valves often arises where the sewing ring and annulus meets.
Infective endocarditis (IE) describes a microbial infection of the endothelial surface of the heart. Valvular involvement is common and characterized by the presence of vegetations. Complications include, but are not limited to, valvular insufficiency, myocardial abscess formation, pericardial effusion, arrhythmia, embolic phenomenon, and congestive heart failure. Factors that predispose a patient to IE include structural abnormality of a heart valve (e.g., bicuspid aortic valve), ventricular septal defect, prosthetic cardiac valve, age, IV drug use, hemodialysis, diabetes, and poor dental hygiene.
IE remains a clinical diagnosis and therefore persistently positive blood cultures, presence of intravascular catheters, pacemakers, physical examination, and history must be taken into account. The DUKE criteria for endocarditis seek to address this point with echocardiography providing evidence of endocardial involvement (a major criterion) if any of the following exist:
Presence of vegetation (tissue-like echodensity with independent motion implanted on the valve, prosthetic material, or endocardium in the trajectory of a regurgitant jet in the absence of alternative anatomic explanation)
Presence of abscesses
New dehiscence of a valve prosthesis
New valvular regurgitation
Transthoracic versus Transesophageal Echocardiography
TTE remains an excellent initial diagnostic test for evaluation of intermediate risk patients for IE (Fig. 14-1). However:
TTE has lower resolution than TEE and can miss vegetations <0.5 cm in size.
Sensitivity of TTE for IE ranges from 40% to 63% with a specificity of 90% to 98%.
If IE is diagnosed with TTE, it should be followed by TEE to evaluate other valves and complications of IE such as abscess, fistula formation, mycotic aneurysm, pseudoaneursym, and leaflet perforations.
TEE is the preferred initial study in high-risk patients by Duke criteria, or in patients who are poor candidates for TTE.
High-risk patients are defined as those with prosthetic heart valves, congenital heart disease, previous endocarditis, new murmur, heart failure, or stigmata of IE.
Proximity of a high frequency TEE probe to the heart allows excellent visualization of the base of the heart and aorta. The aortic and mitral valves are especially well seen.
Sensitivity of TEE for IE is 90% to 99% with a specificity of 91% to 99%.
In patients with a strong suspicion of IE and negative TEE, a repeat TEE 7 to 10 days may be considered to reassess for vegetations.
Vegetation
Vegetations from IE are often a mixture of microorganisms, inflammatory cells, platelets, and fibrin.
They are often found on the leading edge of the affected native valve on the lower pressure side or grow from the annulus if a prosthetic valve is present.
Because of leaflet malcoaptation or destruction, valvular regurgitation is almost always an accompanying feature (Fig. 14-2).
Vegetations may also be seen where regurgitant or fistula flow strikes the endocardial wall, so called “jet vegetations.”
Occasionally, vegetations can cause obstruction and mimic valvular stenosis.
Echocardiographic images should be captured with attention to the following:
Presence, size, shape, and location of vegetations
Valvular hemodynamics
Carefully assess the entire valve to find regurgitant jets
Maximize color Doppler frame rate by reducing the Doppler window
Assess for evidence of volume overload or associated signs of regurgitation severity (e.g., holodiastolic flow reversal in descending aorta in patients with severe AR)
Examine the valvular integrity. Perforation may manifest as multiple jets with turbulence seen on the high-pressure surface of the valve leaflet (Fig. 14-4)
Pacing wires and catheters should also be carefully inspected for vegetations (Fig. 14-5). TEE is preferred to visualize lead infections and also to determine whether the tricuspid valve is affected because of lead artifact.
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