What is the role of intravascular ultrasonography in the workup of

Updated: Apr 09, 2021
  • Author: Sandy N Shah, DO, MBA, FACC, FACP, FACOI; Chief Editor: Yasmine S Ali, MD, MSCI, FACC, FACP  more...
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Answer

IVUS demonstrates the luminal dimensions and, more importantly, the tissue composition of the vascular wall in tomographic subsegments that can be summated to create a 3-dimensional picture showing arterial remodeling and the diffuseness of atherosclerosis with clarity unobtainable by angiography.

IVUS delineates vascular remodeling—positive and negative. Positive remodeling shows adaptive outward expansion of the external elastic membrane to accommodate growing plaques (Glagov phenomenon). Negative remodeling exhibits discrete areas of vascular luminal encroachment by the ingrowing plaques.

Positive remodeling is more commonly associated with unstable angina, whereas negative remodeling is associated with stable angina, according to an IVUS study of 85 patients by Schoenhagen and colleagues. [49]

The apparently paradoxical findings of angiographic studies suggesting that AMI most often occurs in less than 50% of stenosed arterial segments, and those of autopsy studies showing AMI to be associated with large plaques, are reconciled by IVUS findings. IVUS shows the responsible lesions to be large plaques that have positively remodeled, thus causing minimal luminal encroachment and exhibiting echolucency suggesting a lipid-rich pool in the plaque center.

The ability of IVUS to identify positively remodeled plaques and the presence of diffuse disease in some ways makes it better than angiography, the less-than-perfect criterion standard. IVUS can much more clearly demonstrate the presence or absence of fibrosis, calcium, and ulceration, as well as eccentricity of the plaques.

Ostial lesions can also be better defined by IVUS.


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