Barcelona, Spain - Proponents of intravascular ultrasound (IVUS) say it is an essential tool in the cath lab for understanding lesion morphology, deploying drug-eluting stents (DES), and problem-solving post-stent implantation. But in a debate during this year's EuroPCR meeting, not everyone agreed that IVUS offers much over and above angiography with or without functional tests: given the expense of the modality and the expertise required to understand the images, IVUS deserves a place in research laboratories, but not necessarily in every clinical setting, they argue.

According to Dr Gary Mintz (Columbia University, New York, NY), IVUS guidance can influence patient outcomes for the better—particularly in left main disease and other complex lesion/patient settings. While the bulk of the evidence supporting this concept comes from the bare-metal-stent era, Mintz cited unpublished data from Park et al, in Korea, suggesting that using IVUS during left main PCI with DES can improve chances of survival by almost 10% over three years. A second paper in press, by Roy et al, also points to significant reductions in one-year MACE and definite stent thrombosis among DES-treated patients who also underwent IVUS imaging to optimize stent placement. Acknowledging that the evidence supporting IVUS does not come from multicenter randomized trials, Mintz nevertheless points out that the link between underexpanded stents and/or edge coverage and early stent thrombosis is well established. As such, a tool for reducing the risk of suboptimal stent deployment makes sense, intuitively, even if the evidence base does not yet support it, he argues.

"Do you always need level-A evidence to incorporate something into clinical practice?" he asked. "I would submit that the majority of what we do in the cath lab, if you look at every step of the procedure, very little of it meets level-A evidence, and that's just part of what we do as clinicians. . . . For some reason, IVUS is being held to a standard that we don't hold other things to."

Expense, efficiency, expertise an issue

But Dr Jean Marco (Centre Cardiothoracique, Monaco, France), arguing against routine IVUS guidance, pointed out that all of the evidence supporting IVUS is flawed on the basis of study design or size. A randomized clinical trial powered to demonstrate just a 3% difference in clinical outcomes would require 6000 patients, he points out, and no such study exists. A study using the arguably more relevant end point of stent thrombosis would require at least 30 000 patients to reduce the risk of stent thrombosis from 3% to 1.5%, he added.

Marco has no qualms recommending IVUS as a research tool but suggests it should be "optional" in clinical practice. "Routine IVUS guidance of coronary stent implantation is not supported by a critical reappraisal of the available evidence," he concluded.

As for using IVUS for left main procedures, Marco points out that the argument has inherent flaws.

"If we need IVUS and maybe platelet aggregation tests to do a procedure on the left main, the procedure is not a good procedure, and maybe surgery is the better option," he points out.

A recent survey on the EuroPCR website indicated that physicians are not using IVUS because the technology is too expensive, because they don't have the expertise to use it and interpret the images, and because it extends the per-patient procedural time.

Statistics from one of the main IVUS system manufacturers, Volcano, which also supported the debate session at EuroPCR, indicates that IVUS usage varies considerably around the world, from 14% in the US, to 4.5% in Europe, to 60% to 65% in Japan, where it is a reimbursable test. The technology dates back more than 20 years and was first approved during the late 1980s in both Europe and the US. In the DES era, when stent deployment emerged as critical to device safety, IVUS has enjoyed renewed interest as a clinical tool. According to Dr Martin Rothman (London Chest Hospital, UK), who spoke to heartwire following the debate, an escalation in the number of left main procedures is, in part, driving the increased uptake of IVUS.

"For left main disease, after DES implantation, a lot of people who may not have done IVUS before are using it afterward because of the potential, theoretical high risks to patients, just to make sure that the stent is properly deployed."

IVUS is also being used to investigate patients who come back to the cath lab when problems arise poststenting. "Some people, like Jean Marco, point out that there are limited options in terms of what you can do in these patients," Rothman commented. "They say, if you're just going to use a balloon to blow up the hole and expand it again, then why use IVUS? But then, of course, you don't know if you've done any better. If angiography wasn't right the first time, why should it be right the second time? Quite often, people think they've done a good job, and if the patient goes bad subsequently, you've got to ask if the technology for defining 'good' at the outset may not be up to the job."

Marco disclosed consulting for Abbott; Mintz disclosed having major stock/shareholder equity with Volcano and receiving consulting fees and honoraria from Volcano, Boston Scientific, LightLab, Terumo, and Top Spin.