Use of Intravascular Ultrasound in Clinical Trials

Abstract

Intravascular ultrasound (IVUS) permits detailed, high-resolution tomographic imaging of coronary architecture and enables the characterization of atherosclerotic lesions and plaque distribution. This unique value of IVUS easily explains and justifies why IVUS has found easy access to the clinical repertoire of a standard catheterization laboratory. Despite this fact, the contribution of IVUS findings relative to the total number of procedures performed in clinical catheterization laboratories can be considered small, and IVUS is seen primarily as an optional tool accompanying diagnostic or interventional procedures and as a mandatory tool mostly in angiographically ambiguous ostial or bifurcational lesions. In clinical trials, IVUS is used to assess changes that occur in vascular dimensions (remodeling) and plaque distribution during the disease process, during percutaneous interventions and at follow-up. One of the unique features of IVUS is that it is the only method to study remodeling in vivo. A standard image acquisition protocol is commonly applied to ensure premium quality of images and quantitative data. Motorized pullback devices are necessary to obtain reproducible length and volumetric measurements and provide uniform image acquisition. Ultrasound images are analyzed using manual tracing of acoustic interfaces. Since manual tracing is subjective, objective methods are currently being developed to minimize observer involvement. Fully automated segmentation of luminal and medial-adventitial boundaries has recently been demonstrated, but is still regarded as an experimental method. In the design of stent trials, IVUS is partially used to evaluate the effects of stent deployment on patient outcome. IVUS-guided stent implantation has been shown to result in less frequent clinically driven target vessel revascularization than angiographic guidance alone, although mortality and infarct rate are not affected. A current focus is on serial observation of plaque burden in lipid-lowering therapy.

Intracoronary Ultrasound Imaging: Universal Praise, Qualified Adoption

“…The article by Kuecherer [1] in the present issue of Heart Drug provides a detailed and balanced discussion of the current role of intravascular ultrasound (IVUS), as it is perceived in Europe. A number of technical issues that need to be addressed, including the determination of data quality, are mentioned as well.…”

“…From his review of the strength of the available evidence, Kuecherer [1] has to admit that so far, the use of IVUS has not been shown to significantly improve patient outcome. Randomized trials on IVUS-guided stent implantation have not provided concordant results.…”