ABSTRACT
INTRODUCTION When performing coronary angiography to assess the extent and severity of coronary artery disease, clinicians are often faced with lesions that cannot be easily classified as significant or not (i.e., flow limiting and responsible for inducible myocardial ischemia). Typically, a cutoff value of 50% angiographic luminal narrowing is used for this purpose, based on animal studies (and human clinical correlations), showing functional significance at that level of severity. Because such determination is crucial for clinical decision making and because there is significant interand intraobserver variability in this assessment, it is necessary to understand and appropriately use complementary diagnostic tools in many circumstances. Intravascular ultrasound (IVUS), a catheter-based technique, allows cross-sectional imaging of coronary vessels and precise visualization of both the lumen and the vessel wall. Owing to its excellent sensitivity and its very close correlation with histopathology, IVUS is considered the most accurate coronary imaging modality in vivo. It is therefore frequently used to evaluate angiographically ambiguous lesions in the catheterization laboratory.
