4 DISCUSSION
Usually, IE is insidious in onset, variable in symptoms, and critical
with rapid progression and high mortality (>
30%)4, making diagnosis and treatment challenging and
prone to underdiagnosis, late diagnosis, or misdiagnosis.
Echocardiography can clarify the attachment site, size, and shape of the
vegetation and the structural changes of the heart and cardiac
hemodynamic changes caused by various complications5.
The key is how to diagnose vegetation, which requires understanding the
mechanisms underlying IE occurrence. Three conditions must be met for
bacterial IE to occur: the presence of valve thrombus, bacteria in the
circulation, and bacterial growth on the valve1.
High-velocity blood flow damage to the contact surfaces can lead to
thrombosis, promoting vegetation occurrence.
Compared to left heart endocarditis, right heart system endocarditis
shows fevers of unknown origin, bacteremia, and other infection symptoms
and complications caused by right heart system function
damage6. In the first case, various tests suggested
infection, and the ultrasound findings of ventricular septal defect
(prerequisite) and perforated leaflet regurgitation (complication)
allowed a relatively easy diagnosis of the mass as vegetation. In the
second case, it was not easy to distinguish thrombus from infective
vegetation. On the one hand, the patient had congenital heart disease, a
high fever, a high infection index, and evidence pointing to infective
endocarditis, but the blood culture was negative many times. On the
other hand, the patient had whole-body edema, long-term bed rest,
increased blood coagulation function, and the risk of thrombus,
representing a contradiction between the two diagnoses.
The following aspects can distinguish thrombus and vegetation: (1) Mass
nature: the surface of the thrombus is smooth, and the internal echo is
often uneven due to different formation times; the old thrombus is
closely combined with the vascular endothelium and does not fall off
easily; the texture of infectious vegetation is relatively fragile and
easy to rupture and spread, causing infarction and multiple emboli in
small abscesses. (2) Clinical manifestations: the thrombus often has
high-risk factors for thrombosis, such as atrial fibrillation and
myocardial infarction; infectious vegetation has typical clinical
manifestations and signs of infective endocarditis, and the blood
culture is positive. Here, the blood cultures were negative many times
for the two patients, which was related to the use of antibiotics. (3)
Attachment site: the thrombus is often attached to the blood stasis
site, such as the left atrial appendage and apical part, and its
activity is relatively limited; vegetations are often attached to the
valvular blood flow scouring site, with a large activity range, and
infection can spread to adjacent tissues. It often causes erosive
damage, such as valvular ulcer perforation and valve annulus abscess.