Overcoming Barriers to Routine Use of IVUS, FFR & OCT

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Intravascular ultrasound (IVUS), fractional flow reserve (FFR) and optical coherence tomography (OCT) are tools that may be used in a complementary manner and could enhance PCI and patient outcomes. Yet, penetration remains spotty, even in larger facilities.

PROSPECTs of IVUS & FFR

The groundbreaking PROSPECT trial in 2009 found that IVUS, compared with catheter angiography, identified invasive markers of plaque characteristics that may predict future cardiovascular events in patients with acute coronary syndrome (New Engl J Med 2011;364:226-235). Within PROSPECT, researchers evaluated the use of virtual histology (VH)-IVUS imaging, a tool that uses an algorithm to create a colorized picture of plaque to help classify and detect fibrous plaque, fibrofatty plaque, necrotic core and dense calcium.

Lesions identified by VH-IVUS, particularly thin-cap fibroatheromas, were significant predictors of major adverse cardiovascular events. "These plaques would have looked equal on the angiogram and we now have learned that virtual histology is a very positive predictive tool," says Michael C. Foster, MD, a clinical assistant professor of medicine at the University of South Carolina School of Medicine in Columbia, S.C.



Other studies have shown that IVUS can help provide better stent selection, better visualization of plaque and a more accurate determination of occluded vessels compared with angiography. It also can help reduce restenosis rates by providing a more accurate measurement of lumen diameter, plaque area and volume and can ensure proper stent implantation and expansion, says Foster.

But the tool does have confines. "While IVUS is used to assess vessel dimensions and stent implantation, as well as anatomical complications of PCI, it should not be used for lesion assessment in advance of decision making. That is where FFR is needed," says Morton J. Kern, MD, chief of cardiology at the Long Beach VA Healthcare System in Long Beach, Calif.

FFR is used "for any decision point prior to stent implantation in which the operator is uncertain about the significance of a lesion. This applies to all patients with coronary artery disease, post-CABG and post-MI in acute coronary syndromes after stabilization," says Kern.

When Nam et al compared the use of FFR with IVUS to assess intermediate lesions prior to PCI, they found that interventionalists performed fewer PCIs in the FFR arm compared with the IVUS arm (33.7 vs. 91.5 percent) (J Am Coll Cardiol Intv 2010;3:812-17).

Additionally, FAME investigators reported lower rates of death, MI, CABG or repeat-PCI at one year in the FFR group compared with the angiography-guided group (13.2 vs. 18.4 percent). Length of stay and average cost also were lower in the FFR group (3.7 vs. 3.4 days and $5,332 vs. $6,007).

OCT enters the stage

While FFR assesses a lesion's hemodynamic significance and IVUS enhances stent placement, what is OCT's role in the imaging mix? Marco Costa, MD, PhD, director of the Heart & Vascular Institute at University Hospitals Case Medical Center in Cleveland, argues that OCT, with more data, could surpass the use of IVUS in the cath lab.

In fact, a September 2010 report put forth by the Millennium Research Group speculated that as data accumulate and physician adoption increases, the OCT market could grow at an annual rate of almost 60 percent through 2015.

OCT provides a resolution that is greater than IVUS—10 to 15 µm axial resolution and 20 to 25 µm lateral and out-of-plane resolutions—and uses near-infrared light rather than sound to obtain images in only three to five seconds. In comparison, IVUS images are acquired within two to four minutes, says Costa. And, similar to IVUS, OCT is used during a procedure to guide stent selection and can be used post-stenting to evaluate the position and deployment of a stent.

A 2002 study by Jang et al compared the ability of OCT and IVUS to assess coronary plaques, and showed that OCT identified most of the architectural features detected by IVUS and also identified fibrous caps, which can determine plaque vulnerability in lipid-rich plaques (J Am Coll Cardiol 2002;39;604-609). "The high resolution of OCT facilitated the identification of intimal hyperplasia, the internal and external elastic laminae, and echolucent regions, architecture that can be difficult to discern by IVUS," Jang et al wrote.

However, OCT's benefits come at the expense of its limited depth, which is 2 mm compared with the 10 mm depth of IVUS. OCT's limited penetration could make accurate measurements of a total lipid pool and longer vessel segments more difficult.

A more recent study by Sawadal et al comparing the ability of VH-IVUS and OCT to detect thin-cap fibroatheromas (TCFAs) found fault with each technique (Eur Heart J 2008;29:1136-1146). IVUS-derived TCFAs (61 plaques) were defined as an abundant necrotic core (greater than 10 percent of the cross-sectional area) in contact with the lumen and percentage of plaque-volume greater than 40 percent. OCT-derived TCFAs (36 plaques) were defined as a fibrous cap thickness of 65 µm overlying a low-intensity area with an unclear border. Plaques meeting both TCFA criteria (28) were defined as definite-TCFA plaques, leaving 33 IVUS-derived and eight OCT-derived TCFAs remaining. The discordance with IVUS was mainly due to misreading caused by dense calcium, Sawadal et al reported. They concluded, "Neither modality alone is sufficient for detecting TCFA. The combined use of OCT and VH-IVUS might be a feasible approach for evaluating TCFA."

Why so little adoption?

Despite the benefits of these three technologies, adoption rates remain low, partly due to physician uncertainties and resistance to change. "Currently there isn't a uniform interest in these imaging technologies by interventional cardiologists," says Foster.

IVUS and FFR have a class IIa recommendation, meaning the tools may be useful in practice, but are not mandatory. Costa says it is too early to define a recommendation for OCT and perhaps physician adoption is sluggish due to the lack of data. If the American College of Cardiology or the Society for Cardiovascular Angiography and Interventions would give these tools a class Ia recommendation, it may provide a universal agreement that they are beneficial in certain instances, and adoption would increase, Foster notes. European PCI guidelines currently give FFR a class Ia recommendation.

To obtain a class I recommendation in the U.S., Foster says a much larger randomized trial, like PROSPECT, must be undertaken. "There are more than one million stents being placed per year in the U.S., and it is in the public interest to know how to optimally place stents [with the use of IVUS and OCT] and this should be an important public health question to answer," he says.

Foster and his colleagues began using IVUS in 1994 to better understand their patients' arteries and classify plaque. But after stents were introduced and outcomes improved, Foster and colleagues did not see much of a need for IVUS. However, their IVUS utilization picked up again in 2003 during the drug-eluting stent era after witnessing increased rates of thrombosis and restenosis.

IVUS, he says, has helped ensure that stents are adequately expanded within the vessel and, in doing so, has resulted in significant improvements in outcomes.

Often a major issue with adopting these technologies is related to the willingness of the physician and staff, Kern offers. But like any new technology, it takes time for the staff to become trained and comfortable using them—an estimated 10 cases and a course for IVUS and three to five cases for FFR, he recommends. Costa says it took junior faculty at his facility only five to 10 cases with proper training to get comfortable using OCT technology.  

"One of the most complex areas for physicians regarding IVUS is integrating the images into effective clinical decision making in the cath lab," says Gregg W. Stone, MD, director of cardiovascular research and the Education Center for Interventional Vascular Therapy at New York-Presbyterian Hospital/Columbia Medical Center in New York City, and lead investigator of the PROSPECT trial. IVUS-guided PCI doesn't ensure better outcomes unless you interpret the images correctly and use the information to make the right procedural decisions.

Gary S. Mintz, MD, chief medical officer of the Cardiovascular Research Foundation (CRF) in New York City, notes that educational barriers should disappear when more cases are performed. Smaller hospitals, with fewer cases—20 to 40 per year—may have a greater learning curve and the adoption period will take longer.

Reimbursement lagging

Part of the reason for spotty adoption rates of these technologies could be due to their low reimbursement, says Foster. Of the 350 to 400 stenting procedures Foster performs each year, IVUS is used in 80 percent of the cases. But he is an anomaly. The average use in the U.S. is in the 15 percent range.

Conversely, Japan is placing stents under IVUS in 70 to 80 percent of cases, where the technology is adequately reimbursed. Japan is the only country where IVUS is accepted as the standard of care. If U.S. reimbursement were to increase beyond its current $90 to $100 per usage, it could result in more use, Foster says.

FFR usage, on the other hand, has increased due to the 2009 FAME trial, which showed promising results for patients and significant cost reductions for hospitals compared with angiography-guided decisions to stent (New Engl J Med 2009;360:213-224). However, "there is some 'approach avoidance' to the use of this new technology, although the patient outcomes are superior and the cost—particularly to treat multivessel disease—is less than that associated with angiography-guided stenting," offers Kern. The FFR pressure wire is less expensive than a drug-eluting stent, but so is physician income as the $700 FFR wire is not reimbursed to the physician.

"One of the initial reactions to the FAME data is that savings will only be gained though a reduction in costs by lowering the number of stents used," says Habib Samady, MD, associate professor of medicine in the division of cardiology at Emory University School of Medicine in Atlanta. "But fewer stents also could lead to a reduction in the amount of contrast dye and other materials, thus lowering costs further."

An economic analysis by Fearon et al of the FAME trial showed that FFR-guided PCI reduced the per-patient cost of PCI by almost $700 (Circulation 2010;122:2545-2550). In fact, researchers found that the overall costs at one year were less in FFR-guided PCI patients compared to those guided with angiography, $14,315 versus $16,700—70 percent of these cost savings came from procedural costs, while 30 percent came from a reduction in follow-up event rates.

While certain barriers—whether real or perceived—may deter some facilities and physicians from embracing these cath lab tools into routine clinical practice, the available evidence has shown that using them may improve patient outcomes, save initial and downstream costs, reduce the rate of adverse events and better identify vulnerable plaques.

However, more evidence is needed, particularly from well-designed randomized controlled trials, to help persuade clinicians to use these tools more often. Such evidence also could persuade the government to affix a more appropriate reimbursement amount that covers the cost of the technology and the physician's time to use it.

It's a wrongheaded issue not to incorporate the technologies," says Kern. "With these tools, outcomes and decision making are both better.