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Intravascular Ultrasound (IVUS) May Reduce Drug-Eluting Stent Thrombosis by a Third

July 8, 2008 -- A provocative study in the current issue of the European Heart Journal concludes that:

"IVUS guidance during DES implantation has the potential to influence treatment strategy and reduce both DES thrombosis and the need for repeat revascularization."

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The article describes a retrospective observational study of almost 1,800 patients in whom drug-eluting stents had been placed between April 2003 and May 2006 at a single center: the Washington Hospital Center in Washington, DC, where IVUS guidance is used in approximately 70% of coronary interventions.

The patient population was split into two groups (IVUS and non-IVUS) of 884 each, using a propensity-score for matching, in order to minimize any confounding impact due to lesion type, patient characteristics, etc.

The clinical endpoint of the study was definite stent thrombosis at 12 months, which was measured at three intervals: in-hospital, at 30 days and again at one year. The results were striking, surprising even the investigators. At 12 months, definite stent thrombosis had occurred in 0.7% of the patients in whom intravascular ultrasound guidance had been utilized, but in patients where IVUS was not used, the stent thrombosis rate was 2.0%, almost three times higher.

The advantages of IVUS have been written about extensively, but there has never been a study published that showed IVUS benefitted patients with drug-eluting stents in terms of stent thrombosis. Dr. Ron Waksman, corresponding author of the study, told Angioplasty.Org:

"There are some situations in which IVUS tells you a lot: for example, in-stent restenosis. If you want to know whether this is a mechanical issue versus a tissue issue, IVUS is very helpful. If you go to selection of [stent] length and size, that applies to every lesion. Even if you think that you know the size, you may be surprised that you are not accurate just by doing angiography alone. So there are a lot of helpful hints that you can get from IVUS.

"But perhaps the most important one applying to the drug-eluting stent is to obtain sufficient cross-sectional area after deployment of the stent -- to see that indeed the stent is well-expanded, and also well-apposed to the vessel wall. But I think the emphasis is on expansion, because sometimes you can miss on the expansion of the stent without an IVUS. Again, I think systematic use of IVUS post-stenting, enabling you to ensure expansion, to get the ideal cross-sectional area, probably will you get you out of trouble or may in the future."

    Ron Waksman, MD, FACC
Ron Waksman, MD,
FACC, Washington Hospital Center

If a stent is not fully expanded against the arterial wall, the small nooks and crannies left between the stent and wall can be a nexus for platelet aggregation, resulting in a blood clot, otherwise known as stent thrombosis -- which can be very serious. Dr. Waksman explained that most of the stent thrombosis in the study occurred in the first 30 days, and that this type of stent thrombosis is more related to mechanical issues, whereas late stent thrombosis, occurring after a year or more, is more tied to healing and inflammation or responsiveness to Plavix. His study only dealt with the type of stent thrombosis occurring in the first year -- which also occurs more frequently than the late type.

The study also concludes the IVUS guidance "has the potential to influence treatment strategy" because IVUS can show information about the lesion in a way that standard angiography cannot: for example, whether the lesion is eccentric, jagged, calcified in certain areas -- information that might suggest the use of a cutting balloon or Rotablator atherectomy device to pre-treat the lesion and allow the stent to fit more uniformly. In the case of a bifurcation lesion, Dr. Waksman felt that IVUS would be "almost essential" in order to judge whether the two stents have been completely expanded.

The results of the study showed no significant difference in death or MI, but did reveal a trend toward lower target lesion revascularization (TLR) in the IVUS patients (5.1% as opposed to 7.2%) suggesting that IVUS use may also impact the occurence of restenosis.

With IVUS use in the United States hovering in the low teens, Dr. Waksman feels that more interventional cardiologists should be thinking about it. He told Angioplasty.Org:

"I would think that 13% is not sufficient, so there is room to be more liberal with the use of IVUS. The excuse that it's cumbersome is fading slowly because we have now integrated systems, so I think that at this point this is becoming a more essential tool and there are really not many complications associated with it. As to it being time-consuming, it's also becoming relatively simple to use.

"So I would encourage cardiologists to use it more, just based on those results because, now that we've been published, I think that this is an opportunity for even good operators to end with better outcomes. And if that's the case, then it's definitely important also for those who feel less comfortable in the cath lab with complex angioplasty. Here we have a tool that can optimize your result and you should not spare it on the patient."


Reported by Burt Cohen, July 8, 2008