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Use of intravascular ultrasound (IVUS) to guide drug-eluting stent (DES) placement reduces the short- and long-term risk of adverse events, especially myocardial infarction (MI). The findings, from an observational all-comers study, were published in the September 2011 issue of JACC: Cardiovascular Interventions.

Investigators led by George D. Dangas, MD, PhD, of Mount Sinai Medical Center (New York, NY), looked at 1,504 unselected patients who prospectively enrolled in the MATRIX (Comprehensive Assessment of Sirolimus-Eluting Stents in Complex Lesions) registry. All received at least 1 sirolimus-eluting stent between March 2004 and August 2006 at 2 New York City centers. In addition to quantitative coronary angiography, IVUS was performed in 42.0% of the cohort before and/or after implantation at operator discretion.

IVUS, Control Patients Matched

For comparative analysis, 548 of the 631 patients in the IVUS group were propensity-matched with an equal number of controls. Although most clinical and angiographic characteristics were similar between the groups, IVUS patients received less predilation and more postdilation compared with those who did not undergo such imaging. Maximum stent inflation pressure was higher and final stent diameter larger in conjunction with IVUS use.

At 30 days, the IVUS group had lower rates of death/MI, MACE (composite of cardiac death, MI, or clinically driven TVR), and MI but experienced similar rates of mortality and Academic Research Consortium-defined definite or probable stent thrombosis (table 1).

Table 1. Thirty-Day Outcomes

By 1 year, only death/MI and MI still favored IVUS. These differences were maintained through 2-year follow-up, while other outcomes remained equivalent for the 2 groups (table 2).

Table 1. Two-Year Outcomes

 
In the propensity-matched analysis, IVUS predicted 30-day death/MI (HR 0.20; 95% CI 0.06-0.64; P < 0.01) and MACE (HR 0.48; 95% CI 0.24-0.98; P = 0.04) as well as 2-year death/MI (HR 0.53; 95% CI 0.30-0.91; P = 0.02) and MI (HR 0.18; 95% CI 0.06-0.57; P < 0.01).

“Due to its ability to provide additional information on lesion characteristics (pre-intervention) and stent deployment (post-intervention), IVUS imaging plays an important role in optimizing DES placement,” the authors write.

Event rates for the IVUS-guidance vs. angiography-only groups began to diverge soon after the procedure, Dr. Dangas and colleagues note. The reduction in early events in the IVUS group is probably attributable to implantation adjustments enabled by IVUS imaging, they say, whereas later events were more likely due to disease progression or the biologic effects of the DES and unaffected by IVUS use.

Case for IVUS Observational But Growing

In an e-mail communication with TCTMD, coauthor Bimmer E. Claessen, MD, of the Academic Medical Center (Amsterdam, The Netherlands), cautioned that “although our study supports use of IVUS-guided PCI in routine clinical practice, and is consistent with a number of prior reports by other sites with high IVUS usage, it is limited by its observational nature.”

However, Dr. Claessen reported that the ADAPT-DES trial, which includes a 3,000-patient IVUS substudy, and the IVUS-XPL trial have begun enrolling subjects. These “will finally provide data from randomized controlled trials to confirm or disprove prior reports on the benefit of IVUS in the DES era,” he said, adding that it would also be interesting to see in those trials whether the extra upfront cost of IVUS is offset by the savings achieved by reducing clinical events.

Massoud A. Leesar, MD, of the University of Cincinnati (Cincinnati, OH), pointed out to TCTMD in a telephone interview that one factor impeding broader IVUS use in the United States is low reimbursement, which is currently set by the Centers for Medicare and Medicaid Services at about $110.

Despite the technology’s ability to improve stent placement in many scenarios, it is not mandated in the guidelines because of the lack of randomized studies, Dr. Leesar said. But he predicted that if the situation changes, clinicians will put more effort into learning the technique and will use it more frequently.

Currently about 15% to 20% of US physicians use IVUS—compared with about 70% of those in Japan—but that percentage has doubled over just the past few years, John McBarron Hodgson, MD, of the Geisinger Health System (Wilkes-Barre, PA), told TCTMD in a telephone interview.

Reasons to Resist IVUS Diminishing 

Part of the reason is growing evidence of its clinical impact, Dr. Hodgson indicated. “We’ve seen a very consistent trend in 4 [DES] studies now, and it matches the [earlier] trend in BMS,” he said. “While purists would say we don’t have a huge randomized double-blind trial and therefore we can ignore everything, the reality is that 20 years’ worth of incremental data puts the weight of evidence clearly in favor of IVUS guidance for a host of [situations].”

In addition to having what Dr. Hodgson characterized as a head-in-the-sand attitude toward the evidence, some clinicians say they skip IVUS because they cannot take the extra time or are not sure how to interpret the images. But the latter excuse no longer holds up, he said, because the fundamentals are fairly simple and machines now do much of the work. “The only thing that’s left to operators is to make sure they’re in the right vessel and the right spot when they make measurements,” he added.

One of the most common mistakes that preprocedural IVUS imaging can help avoid is underestimating the size of the stent required, Dr. Hodgson said. And unlike angiography, IVUS can show during the procedure when inflation pressure is inadequate. “We know that leaving stents underexpanded will lead to higher restenosis,” Dr. Hodgson said. Although suboptimal stent apposition has also been associated with stent thrombosis, he added, the impact is much less straightforward because the cause is multifactorial.

The more critical the disease and the more difficult the anatomy, the more important it is to add IVUS guidance, Dr. Hodgson said.

Study Details 

IVUS catheters used in the study included Atlantis S (40 MHz, Boston Scientific, Natick, MA) and Eagle Eye (20 MHz, Volcano, Rancho Cordova, CA).

All IVUS studies were performed after intracoronary administration of 100 μg to 200 μg of nitroglycerin. The catheter was advanced more than 5 mm distal to the lesion, and imaging was performed using an automated pullback device to the proximal reference at a pullback speed of 0.5 mm/s. 

Note: Dr. Dangas and several coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD. In addition, coauthor Gary S. Mintz, MD, serves as medical director and editor-in-chief of TCTMD.

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