Role of intravascular ultrasound in the evaluation of mechanisms of coronary interventions and restenosis.

Intravascular ultrasound (IVUS) has emerged from being a research tool to becoming an intrinsic part of modern invasive cardiology. The main reason is its ability to obtain "in vivo" microanatomy. For the first time it is possible to base decisions not only on lumenograms but also on vessel wall assessment. The intervention-associated potential of IVUS includes the ability to allow optimal device selection, i.e., rotablators in calcified lesions or atherectomy devices in large plaque burden. The effects of percutaneous transluminal coronary angioplasty (PTCA) on vessel-wall morphology can be studied in great detail and the effect on luminal gain can be assessed almost on-line. Several groups have showed that the residual plaque area, even after angiographically successful PTCA, still lies in the range of 60%. A significant reduction of this percentage may influence long-term outcome after PTCA. Minimal luminal areas and residual plaque area after PTCA seem to be an indicator of restenosis, whereas the presence or absence of dissections seem to be less predictive. The main mechanism of restenosis after PTCA is vessel shrinkage, not intimal hyperplasia. Intravascular monitoring of stent expansion led to high-pressure stent deployment with a significant increase in postprocedural luminal diameters and finally the ability to withhold anticoagulation in patients with optimal stent deployment.