Assuring optimal stent deployment with the use of intravascular ultrasound (IVUS) during drug-eluting stent (DES) implantation appears to reduce stent thrombosis as well as the need for repeat revascularization, according to a new study published online June 11, 2008, ahead of print in the European Heart Journal.
Researchers led by Probal Roy, MD, of the Washington Hospital Center (Washington, DC), looked at definite stent thrombosis and major adverse cardiac event (MACE) rates in 884 patients undergoing IVUS-guided intracoronary DES implantation between 2003 and 2006. Dr. Roy and colleagues compared these data with a propensity-matched population receiving DES with angiographic guidance alone.
At 30 days, a lower rate of definite stent thrombosis was evident in the IVUS group compared to the non-IVUS group (0.5% vs. 1.4%; P = 0.046).
At 12 months, there were no significant differences between the groups in late stent thrombosis (>30 days), MACE, or death. The difference in cumulative definite stent thrombosis rates remained significant in favor of the IVUS group, which also showed a trend toward less target lesion revascularization (TLR) (table 1).
Table 1. 12-Month Outcomes of DES Patients Receiving IVUS vs. Angiography Alone
IVUSn = 884
No IVUSn = 884
Late Stent Thrombosis
Definite Stent Thrombosis
aMACE, death, Q-wave myocardial infarction, and target vessel revascularization.
IVUS guidance was an independent predictor of freedom from cumulative stent thrombosis at 12 months (adjusted HR 0.5, 95% CI 0.1-0.8; P = 0.02).
The authors suggest that the lower 12-month rates of definite stent thrombosis in the IVUS group were driven by the decreased rate of subacute (1-30 days) stent thrombosis. There were no differences between groups in late stent thrombosis, a fact the authors explain by implicating different factors in the development of each type of stent thrombosis.
“It is reasonable to assume that the underlying mechanisms of subacute stent thrombosis after both implantation of [bare-metal stents] and DES remain the same, predominantly mechanical, . . .” they write. “The failure of IVUS guidance to impact late stent thrombosis suggests the predominance of non-mechanical etiologies such as delayed endothelialization, late malapposition, and hypersensitivity.”
IVUS guidance may reduce subacute stent thrombosis by optimizing stent deployment. Deployment-related problems known to be associated with subacute stent thrombosis include stent under-expansion, malapposition, inflow/outflow disease, dissection, thrombus, and tissue prolapse.
The researchers also note that IVUS may have impacted clinical outcomes in the study by providing information to the interventionalist that led to differing treatment approaches.
In a telephone interview with TCTMD, coauthor Ron Waksman, MD, also of the Washington Hospital Center, said that nationwide use of IVUS in catheterization laboratories is about 12%, which is too low. “If we can save a few lives by generalizing this technology to a larger population, it’s worth it. And this study, although it is not definitive, suggests clearly there is a benefit to broader use of IVUS,” he said.
IVUS is underutilized in the cath lab, Dr. Waksman explained, mainly because of logistics. “Cost is probably not the main motivation for it not being standard,” he said. “The reasons for low rates of use are things like the practicality of moving something like a washing machine into the lab. It’s time-consuming, asking where it is, how long does it take to set up, and then there is the question of understanding the image. There is a learning curve–you have to have someone who is dedicated to the technique.”
Dr. Waksman said that using IVUS should become simpler in the future as training and technology are improved. “I think with the notion that this may reduce stent thrombosis, we will see [IVUS] used more,” he said. “Use has already increased about 4% from 2006.”
Marco Costa, MD, of University Hospitals Case Medical Center (Cleveland, OH), told TCTMD in a telephone interview that he thinks the study is interesting and provides convincing reasons to move toward a larger, randomized trial evaluating IVUS use in angioplasty.
“Optimal stent deployment is of paramount importance for outcomes of DES patients, and these results are promising,” Dr. Costa said. “But we need to be careful, as this is a high-volume center with highly skilled operators using IVUS, so whether those results apply to less experienced IVUS operators remains to be determined.”
Dr. Costa also noted that the study did not specify precisely how IVUS was used. “It was not clear who was receiving IVUS pre-intervention, post-intervention or both, or whether IVUS improved lumen area or vessel size. This message that IVUS, no matter how you use it, will benefit patients needs to be refined so that we can learn not just how to use IVUS, but how to use it optimally.”
Roy P, Steinberg DH, Sushinsky SJ, et al. The potential clinical utility of intravascular ultrasound guidance in patients undergoing percutaneous coronary intervention with drug-eluting stents. Eur Heart J 2008;Epub ahead of print.