Application of intravascular ultrasound to characterize coronary artery disease and assess the progression or regression of atherosclerosis.

Angiography has major limitations in its ability to assess coronary disease. Intravascular ultrasound (IVUS) offers unique capabilities to assess coronary atherosclerotic burden. The tomographic orientation of ultrasound enables visualization of the full vessel wall, as opposed to the 2-dimensional projection of the lumen provided by angiography. The equipment required to perform coronary IVUS consists of a catheter with a miniaturized transducer and a console to reconstruct the image. High ultrasound frequencies are used, typically, 30 to 40 MHz, which provides excellent theoretical resolution. IVUS has been performed safely in a wide variety of clinical situations. Vessels with classic atherosclerosis exhibit a diversity of abnormal features that reflect the severity, composition, and distribution of the atheromata. Plaque rupture is sometimes evident in ultrasound examination of the culprit lesions after an acute coronary syndrome. Most laboratories routinely perform cross-sectional area measurements of the lumen and external elastic membrane boundaries and calculate atheroma area. IVUS commonly detects atherosclerosis at angiographically normal sites. It has contributed substantially to our understanding of remodeling and has shown that positive remodeling is more prevalent in unstable lesions. Studies in patients early after transplantation have shown the presence of advanced atherosclerosis in their apparently normal donors. In addition, the application of IVUS in detecting the rate of progression or regression of existing atherosclerosis is among the most dynamic areas of development. IVUS is likely to emerge as the "gold standard" in the study of atherosclerosis progression-regression over the next few years.