Volumetric intracoronary ultrasound: a new maximum confidence approach for the quantitative assessment of progression-regression of atherosclerosis?

Quantitative assessment of atherosclerosis during its natural history and following therapeutic interventions is important, as cardiovascular disease remains the most significant cause of morbidity and mortality in industrial societies. While coronary angiography delineates the vessel lumen, permitting only the indirect determination of atherosclerotic wall changes encroaching upon the lumen, intracoronary ultrasound permits direct plaque assessment and quantification. The angiographic percent diameter stenosis, previously suggested as measure of a maximum confidence approach, is still commonly used to quantify stenosis severity, but the reference segments which are required for angiographic interpolation of the normal vessel dimensions are frequently involved in the general process of atherosclerosis, including progression or regression. Considering also the variability of vascular remodeling during the evolution of atherosclerosis, including compensatory enlargement and paradoxical arterial shrinkage, intracoronary ultrasound appears currently to be the only reliable technique to measure plaque burden and progression or regression of atherosclerosis. However, correct matching of the site of measurement at follow-up with the site of the initial ultrasound study is often difficult to achieve, but is significantly facilitated by the use of volumetric intracoronary ultrasound. This approach permits not only area measurement, but also measurement of plaque volume, which appears to be the ideal measure for quantifying the atherosclerotic plaque, as it is highly reproducible and directly reflects the changes of an entire arterial segment.