The significance of intravascular ultrasound in differential diagnosis and therapy of coronary stenoses

Intravascular ultrasound (IVUS) has emerged from being a research tool to becoming an important aspect in invasive cardiology, because it offers the possibility to obtain "in vivo" histology, including the vessel wall, while angiography allows for lumenograms only. The reasons for performing IVUS can be divided into either diagnostic or intervention associated indications. Diagnostic strength of IVUS is the ability to monitor compensatory coronary artery enlargement as a response to arteriosclerosis, to reveal occult left main stem disease, and angiographically "silent" arteriosclerosis. The peri-interventional potentials of IVUS are the ability to allow optimal device selection, i.e., rotablators in calcified lesions or atherectomy devices in large plaque burden. The effects of PTCA on vessel wall morphology can be studied in great detail and the effect on true luminal gain assessed almost on-line. Several groups showed that the residual plaque area after angiographically successful PTCA lies in the range of 60%. A significant reduction of this number may influence long-term outcome after PTCA. Minimal luminal areas after PTCA seem to be an indicator of restenosis, while the morphological appearance alone seems to be less predictive. Intravascular monitoring of stent implantation led to high-pressure stent deployment with significant increase in postprocedural luminal diameters and, finally, the ability to withold anticoagulation in patients with optimal stent deployment. Furthermore, integrated devices, like balloons on IVUS catheters, steerable catheters, integrated flow measurements and pressure transducers will further increase the usefulness of IVUS.