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Intravascular Ultrasound (IVUS) Use Growing with Integration into Routine Cath Lab Imaging

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May 15, 2008 -- Intravascular Ultrasound, or IVUS (pronounced "eye-viz") is an imaging technology that looks at arteries from the inside out. Invented two decades ago, IVUS recently has been gaining in usage due to safety concerns about stent thrombosis: cardiologists who use the technology feel that IVUS guidance adds a measure of precision for proper stent placement and expansion during angioplasty.

A second reason the use of IVUS is on the rise is that the technology has been made easier to use.

IVUS consists of a tiny ultrasound imaging device, mounted on a catheter that can be threaded across a section of artery to yield both a cross-sectional and longitudinal view, showing the amount and shape of plaque and whether or not a stent is has been optimally deployed and expanded -- information that is not shown by standard angiography.

Volcano s5i Integrated Display
Volcano s5i Integrated Console Displays Both IVUS and Angiographic Images

The first generations of intravascular ultrasound equipment consisted of a separate console that had to be wheeled out and booted up to use. The result was that the equipment very often sat on the sidelines.

However, today's IVUS can be integrated into the primary catheterization lab imaging console. For example, Volcano Corporation (Nasdaq: VOLC), one of only two U.S. manufacturers of IVUS systems, has partnered with all four major cath lab suppliers, GE, Philips, Siemens and Toshiba, and yesterday Volcano announced the 1,000th worldwide installation of its s5 and s5i integrated imaging consoles.

As evidence of this recent increase in adoption, Volcano has posted sales gains of 25-35% for the past two quarters. And increasingly IVUS is being utilized in centers that have strong fellowship programs, training future interventionalists. At one such center, the Dartmouth-Hitchcock Medical Center in New Hampshire, the Director of the Cardiovascular Catheterization Laboratory, Dr. Craig A. Thompson, explains the importance of IVUS integration:

"I think the current generation IVUS integrated table side systems really streamline the process in terms of maintaining cath lab case and turnover efficiency, and frankly, their edge detection and imaging chain algorithms are becoming simpler to use, so that some of the historic barriers to being able to use IVUS efficiently and interpret the images and use that to possibly modify the intervention are improving.

"I think just the simple integration of IVUS systems at bedside is a huge benefit. It is tremendous! I think it’s something that just cannot be adequately captured -- this is incredibly beneficial. Because of that and the recurrent emphasis on having very good technique in stent deployment and device utilization, I think IVUS is going to have a resurgence."

    R. Lee Jobe MD
Dr. Craig A. Thompson, Dartmouth-Hitchcock
Medical Center

For many years, intravascular ultrasound has been used as a research tool. Its ability to measure precisely both the thickness and distribution of intracoronary plaque has mandated its use as part of many clinical trials -- judging not only the efficacy of drug-eluting stents, but also various pharmaceuticals, such as statins, and whether or not they can stop or even reduce plaque.

Two recent drug-eluting stent trials, for Medtronic's Endeavor and Abbott's XIENCE, both have had positive results, but an interesting sidelight is that in trials for both stents, the Japanese arms showed significantly better outcomes in terms of "late loss", a measure of how much tissue has regrown inside the stent.

Dr. Shigeru Saito
Dr. Shigeru Saito of Kamakura, Japan during live course

Angioplasty.Org asked Dr. Shigeru Saito, the principal investigator of the Japanese studies for both clinical trials, why that might be. He replied simply, "IVUS -- in Japan IVUS is reimbursed so we use IVUS much more." Dr Saito, who is Director of Cardiology and Catheterization Laboratories, Shonan Kamakura General Hospital, explained how IVUS showed that sometimes the stent required further expansion:

"Before using IVUS, we were very happy just looking at the cine [angiography]. But after doing IVUS, we were not happy because the stent was not fully expanded.The most important thing about using IVUS is that we can exactly see whether the stent is fully expanded or not -- and the second thing: is the stent is fully apposed to the vessel wall? It's very important in terms of the long term stent thrombosis."

One of the ongoing challenges for the wider dissemination of IVUS has been to make the standard of care that is present in highly monitored clinical trials available to practitioners and their patients on a daily basis. It is in this area that the integrated and easier-to-use intravascular ultrasound technology has been making inroads. Dr. Michael C. Foster, MD, of the South Carolina Heart Center, told Angioplasty.Org how that has been working in his lab:

"If we use an integrated system, there really is no significant increase in the procedure time, and you’re not adding the personnel costs.... There’s no bringing in a machine, turning it on, waiting for the computer to boot up, and then a technician adding the name, the age, birth date, none of that has to be done....

"I would call it a plug-and-play environment, and you instantaneously have your pictures. In about one minute, I can get the IVUS set and do a pull-back into the artery that I'm interested in. And, of course, I’m looking at the images as I'm pulling back, and I'll usually spend another minute or two, on an interesting case, manipulating images, maybe making some measurements, and so forth. So from soup to nuts, we’re talking about three minutes to do IVUS."

    Dr. Michael Foster
Dr. Michael Foster, South Carolina
Heart Center

Proponents of IVUS, as well as other new imaging technologies, feel that these tools have an important role in patient safety and in improving procedural outcomes -- even in the era of second generation drug-eluting stents.

As former President of the Society for Cardiac Angiography and Interventions (SCAI), John McBarron Hodgson, MD, told Angioplasty.Org:

John McBarron Hodgson, MD
John Hodgson, MD
Phoenix, Arizona

"I don't care if you've got a balloon, a cutter, a zapper, a laser, whatever...whether you want to call the stent a XIENCE, or put it on a Vision, it doesn't make any difference. You still have to make sure that you've got a good opening, and the only way that you can do that effectively is with IVUS.

So, I don't care what they develop in the future -- we need a way to ensure that we have mechanically opened that vessel in the best way possible, and it depends on the plaque distribution, the plaque burden, the plaque calcification, etc., and the only way you can reliably look at that is with intravascular ultrasound.


reported by Burt Cohen, Angioplasty,Org, originally published May 13, 2008 / updated May 15, 2008