[Intracoronary ultrasound: A necessary tool for stent implantation? Arguments in favor]

Intracoronary ultrasound (ICUS), as opposed to angiography, provides high resolution, tomographic images of the coronary vessel and lumen. Because of its superior diagnostic sensitivity ICUS is indicated in the evaluation of suboptimal results and complications following stent implantation. Only a few years ago the use of stents was limited by a high incidence of subacute thrombosis. ICUS demonstrated that the deployment technique used at that time was inadequate and that stent expansion could be improved by the routine use of high pressure inflation, leading to a simplification in the anticoagulation regimen and a decrease in the subacute thrombosis rate in elective procedures to < or = 1%. However, the routine use of high balloon pressures does not assure an adequate expansion of the stent. Only about one third of the stents deployed under angiographic guidance are optimally expanded, with intra-stent luminal dimensions similar to the adjacent, reference, luminal sizes. Significantly, these underdeployed stents can be recognized by ICUS and a large proportion adequately expanded. It should be emphasized that the best predictors of stent restenosis are two ICUS parameters, the postprocedural luminal dimensions and the % cross sectional narrowing, and not the angiographic parameters. Likewise, two of the lowest restenosis rates ever reported (12.8% and 7.3%) have occurred in two studies (WEST-2 and MUSIC) in which stent deployment was guided by ICUS. Two trials (AVID and OPTICUS) have been specifically designed to test the hypothesis that routine use of ICUS to guide stent implantation could diminish the restenosis rate, but their final results are not yet available. The CRUISE study was designed to evaluate the impact of routine ICUS not on angiographic restenosis but on the clinical need of revascularization. In this trial, the larger luminal dimensions of the stents implanted under ICUS guidance translated into a 40% reduction in the 6 month revascularization rate (14.8% vs. 8.9%, p < 0.05). Although the final answer is still pending, the available information suggests that the routine use of ICUS might translate into a direct clinical benefit, something remarkable for a diagnostic tool. In any case, the most effective way of using ICUS would probably be identifying those lesions that most benefit from the technique and avoiding its use in lesions with, a priori, excellent results.