PCI Tools Provide Guidance for the Gray Zone
Interventional cardiologists are under the gun to ensure that only patients who will benefit from PCI undergo the procedure. But strict adherence to appropriate use criteria could actually harm patients who don't fall within categories used to define the criteria. Tools, such as fractional flow reserve (FFR), intravascular ultrasound (IVUS) and optical coherence tomography (OCT), won't eliminate what cardiologists term the gray zone—those ambiguous cases that fall between appropriate and not—but they may provide evidence to help clinicians use good judgment.

Appropriate use pros & cons

For interventional cardiologists, appropriate use criteria may be a mixed blessing. On one hand, the appropriate use criteria (AUC) spelled out by the American College of Cardiology (ACC) Foundation Criteria Task Force in 2009 (J Am Coll Cardiol 2009;53[6]530-553) showed a good-faith effort by the cardiology community to proactively ensure quality care for patients at a time when overuse of PCI was making nationwide headlines. On the other hand, the guidelines do not represent the spectrum of patients seen in clinical practice, sometimes putting clinicians who handle complex cases at odds with benchmarks that some suggest are imperfect and outdated.

"It is never as simple as to establish these criteria to determine whether a procedure is appropriate or not," says Craig A. Thompson, MD, an interventional cardiologist at Yale University Medical Center in New Haven, Conn. "There is some black and white, but there is a big gray scale where one needs to be permissive. If you are too strict then all of sudden you could be detrimental to patient care."

Some decision-making and assessment tools have gained traction in the past decade that may help interventionists navigate the gray. Cardiologists can apply FFR and IVUS, for instance, to assess lesions and determine whether or not to intervene. If they decide to proceed with PCI, they can use the imaging capabilities of IVUS or OCT to select stent size and ensure the stent is properly implanted. Personal preference and experience seem to be driving the adoption of these technologies, which could improve patient outcomes and contain costs. But need, skill and good clinical judgment must align to achieve maximum value.

"Certainly these technologies are going to have a role in improving quality of care and some may create benchmarks that will be rolled into appropriateness and decision-making," says Thompson. He adds that no one test will definitively categorize a procedure as appropriate but the tools will add value if they are applied judiciously and their results are interpreted correctly. "The more quality information that informs the decision matrix, the better off a physician will be. At a minimum, the standard of care and process of care will be improved with these technologies."

Eliminating inappropriateness

In-stent restenosis with dissection: OCT provides high-resolution tissue characterization. Source: St. Jude Medical
The evidence-based AUC are designed to ensure that the literature is used efficiently to provide quality care. They are intended to assist but not supplant clinical decision-making, the AUC authors wrote, and are not a surrogate for experience and judgment.

In a landmark study on PCI appropriate use, Paul S. Chan, MD, a cardiologist at Saint Luke's Mid America Heart and Vascular Institute in Kansas City, Mo., and colleagues found that 98.6 percent of PCIs for acute MIs were deemed appropriate, while almost 12 percent of procedures performed on non-acute patients were classified as inappropriate. The study applied the appropriate use criteria to 500,154 PCIs submitted to the ACC's National Cardiovascular Data Registry between July 1, 2009, and Sept. 30, 2010 (JAMA 2011;306[1]53-61).

Chan says that the appropriateness rate could be improved but there always will be exceptions. "There are situations where the AUC would deem a procedure as inappropriate or uncertain but, in fact, for a particular patient, it may be very appropriate to perform the intervention," Chan says. Conversely, he envisions scenarios where PCI would be inappropriate although it meets the appropriateness standard.

"Clinical decision-making can't be cookie cutter," he emphasizes. "That is why the inappropriate rates are never expected to be 0 percent, and in many ways, they shouldn't be 0 percent because it then removes the clinician from the loop of clinical judgment."

FFR as a decision-making tool

The FAME study lent credibility to FFR when it found use of the pressure wire technology led to significantly lower mortality rates, MI and repeat stenting. Use of FFR was particularly helpful in assessing intermediate lesions with narrowing between 70 and 90 percent (N Engl J Med 2009;15;360[3]:213-224).

"We saw a sea change [after FAME]," says Morton J. Kern, MD, associate chief of cardiology at the University of California Irvine Medical Center. "Ten years ago, no place had heard about it. Now, FFR is one of the tools to help us align outcomes and cost better."

FFR is an assessment tool, and not appropriate in all circumstances. It is usually unnecessary in severe and moderate cases, as shown in the FAME study.

"If you perform an angiogram, which shows minimal disease, most people do not recommend doing an FFR at that point," says Jonathan M. Tobis, MD, director of interventional cardiology at the University of California, Los Angeles. "On the other hand, if the disease is very severe, 90 percent, then you don't need FFR. You just can proceed with the procedure, assuming that there are appropriate indications."

"FFR can bring a lot of value," says Thompson. FFR is helpful for dealing with cases that fall in the gray zone, he says, especially with unclear blockages on angiograms. However, he cautions that FFR validation was done with stable patients and may not be as valuable in patients with unstable conditions.

IVUS and OCT for anatomic assessment

Unlike FFR, IVUS is an imaging technology that allows cardiologists to visualize anatomical features of the vessel. It provides more detail than an angiogram and can be helpful in selecting proper stent size, ensuring optimal stent placement and deployment. Kern prefers FFR to assess physiology and IVUS to assess anatomy. He says FFR should answer whether to proceed and IVUS should address how. Thompson says he prefers IVUS over FFR as an assessment tool in more complex cases, and will start with IVUS in procedures that likely will require IVUS anyhow. Tobis, however, argues that it is an individual choice.

"There are proponents of each technique," Tobis says. "There are people who don't trust FFR results. It is somewhat technique dependent, which is the argument for looking into the anatomy. The biggest impediment with IVUS is that people don't feel comfortable interpreting what they see, especially in terms of characterizing the tissue."

OCT, which uses near infrared light, is fast and provides detailed morphology but is limited in depth and requires blood removal. Compared with the U.S., the technology is more commonly used in Asia and Europe, where it's been on the market longer. OCT received FDA approval in 2010.

Thompson says he uses OCT if he questions the quality of the PCI outcome. "It is a powerful tool in terms of understanding stent deployment, how well the stent is pressed against the vessel and apposition, and if there are any problems with the vessel such as a dissection or a mild injury to the vessel," Thompson says. "You get phenomenal detail with OCT."

Technology's influence on practice

As with evidence-based guidelines, appropriate use criteria are based on somewhat outdated data that may not reflect current practice and state-of-the-art knowledge. Chan says the AUC committee already is working on a new iteration.

"The guidelines should really be renamed as an estimate of what we know," Tobis suggests. In the meantime, the practice of cardiology is being influenced by these technologies even if they are not actively used, cardiologists say. Interventionists may choose to apply higher pressure and larger balloons when deploying stents, for instance, because of positive results from IVUS-based studies.

"People know the results of IVUS-guided stenting, therefore they have altered the way they conduct stenting guided by angiography, so the [IVUS-guided vs. angiography-guided] results aren't significantly different. There may be a 5 percent difference in restenosis, but not dramatic," Tobis says.

Thompson adds that experience gained through such PCI tools may inform decisions, even in their absence. "Even when not using IVUS, it helps to recalibrate the eyes to provide a better 3D image in your mind of what you are seeing on a 2D angiogram," Thompson says. "People have become better operators even when they are not using IVUS because they understand that the vessels are a little larger than they tend to think they are when they look at an angiogram."