Intravascular ultrasound assessment of ambiguous coronary lesions

Accurate assessment of coronary lesions is essential for clinical decision-making. While angiography has long been accepted as the gold standard investigation, this technique provides only a planar 2-D silhouette of the arterial lumen and therefore has limited accuracy in the setting of vessel tortuosity or overlap, bifurcational and eccentric lesions, and diffusely diseased arteries. By providing high-resolution cross-sectional imaging through the arterial wall, intravascular ultrasound (IVUS) can overcome many of these limitations and accurately quantify angiographically indeterminate lesions. Angiographic evaluation of the left main coronary artery presents particular challenges that are ideally resolved with IVUS examination. The role of IVUS in the assessment of coronary stenoses of angiographically intermediate severity (50-70%) continues to evolve. Recent data correlating IVUS with intracoronary flow and pressure measurements suggest that epicardial coronary artery lesions with minimum lumen area of less than 3-4 mm2 may be haemodynamically significant. In addition to accurately quantifying minimum lumen diameter and area at the lesion site, IVUS can characterise coronary artery plaque morphology, and it may have the potential to predict plaque complications.