For interventional cardiologists, there is no more Solomonic decision than knowing when to stent or medically treat a suspicious lesion. Technology has given physicians a helping hand, first through angiographic guidance—the gold standard for decades—and, more recently, through tools like fractional flow reserve (FFR), intravascular ultrasound (IVUS) and optical coherence tomography (OCT). Though the benefits of these devices have been shown, their usage for PCI remains spotty. How will the debate over when to use these technologies play out, and which tools, if any, are likely to emerge the winners?
The 60-year-old patient on the cath lab table at the VA Long Beach Health Care System in California was a veteran in more ways than one. A previous stent recipient with multiple coronary risk factors, he was now experiencing intermittent substernal chest pressure that had worsened over the prior three months. Imaging showed a new lesion in front of the previous stent resulting in a 60 percent narrowing, while a small diagonal branch looked ratty and diseased on the monitor. A textbook case for revascularization? Not so fast was the decision of Morton Kern, MD, chief of medicine at the health system, and his cath lab team. Instead, they opted for FFR—and were rewarded. The procedure showed the diagonal branch to be near-normal, and non-obstructive coronary artery disease in the other vessel despite its 60-75 percent lesion. Optimal medical therapy was begun, and the patient was soon back to his normal daily routine, free of any symptoms.
“Without FFR, it’s 100 percent certain we would have gone ahead with another stent,” says Kern. “And aside from cost, it could have triggered an event during implantation, or restenosis or late thrombosis when the patient stopped his medicine after a year. The right answer in this case was medical therapy and follow-up.”
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On the strength of the FAME (Fractional Flow Reserve versus Angiography for Multivessel Evaluation) and FAME-2 trials—which showed a significant reduction in major adverse cardiovascular events with FFR-guided intervention in patients with stable coronary disease—FFR usage has grown. An analysis of U.S. trends in FFR utilization after publication of the FAME trial by a team from the University of Arkansas for Medical Sciences showed an 18-fold increase in the number of FFRs and a 16-fold increase in FFR-guided PCIs from 2008 to 2012. Intriguingly, the number of PCIs fell by 28.2 percent during that period. The probable reason is not lost on Naga Pothineni, MD, a general cardiologist at the University of Arkansas for Medical Sciences and member of the “U.S. Trends” team that reported its findings in a letter in the Journal of the American College of Cardiology in February (2016;67[6]). “It appears that more and more interventionalists are doing a physiological assessment of lesions through FFR and performing PCI only if it’s indicated,” Pothineni explains. “Most importantly, they’re avoiding unnecessary PCIs, no small achievement when you consider every PCI comes with its own set of complications.”
Despite the upward trend line, overall usage of both FFR and IVUS remains relatively low. FFR was employed 6.1 percent of the time and IVUS 20.3 percent in 2010, according to recent data from the National Cardiovascular Data Registry. Driving physician decision-making in the field is a welter of medical, cultural and business factors, including convenience, personal preference, resistance to change, appropriate use criteria and time concerns. Reimbursement also may play a role. Under its 2016 Procedural Payment Guide, for example, Medicare reimburses physicians less than $100 for an FFR or IVUS procedure compared to $631 for non-drug eluting stent coronary revascularization.
Kern further highlights the impact of economics on decision-making. “Hospitals have an intrinsic conflict of interest because these tools may end up reducing the number of PCIs and bypass surgeries, which are huge revenue boosters for them,” he argues. “What then is the incentive to use them? Only that they would be providing state-of-the-art medicine to patients and that use of these tools would be a compelling draw relative to their competitors, who are practicing old medicine.”
Competitive or complementary?
The debate over the use of anatomic and physiologic guidance for PCI has been further complicated by long-simmering questions over which technology—FFR, IVUS, OCT or others—is most appropriate. FAME and other studies have underscored the ability of FFR to determine lesion severity and which, if any, stenoses need stenting. IVUS has been shown in major studies like PROSPECT (Providing Regional Observations to Study Predictors of Events in the Coronary Tree) and ADAPT-DES (Assessment of Dual Antiplatelet Therapy with Drug-Eluting Stents) to provide better visualization of blockages than angiographic imaging, as well as improved stent selection and reduced rates of restenosis and stent thrombosis. On the strength of its high resolution and use of near-infrared light (vs. sound) to produce images in only three to five seconds, OCT has been adopted by a growing number of physicians and could eventually overtake IVUS in the cath lab, according to some experts.
Indeed, because of the unique capabilities of each, these technologies are increasingly seen as complementary, rather than competitive. “Ideally, you should do both,” emphasizes Gus Pichard, MD, senior consultant with MEDSTAR Heart & Vascular Institute in Washington, D.C. “FFR is indispensable to deciding whether or not to treat a lesion. IVUS plays a different role. It’s indispensable to understanding the nature of the blockage and what the length and make-up of the plaque are, and can thus match you to the optimal treatment. In our lab, I do IVUS in almost 100 percent of cases. It makes PCI faster and safer with less stent thrombosis and improved patient outcomes.”
Pothenini echoes that thought. “Additional assessment of intermediate lesions is going to become the norm, and modalities like IVUS and OCT will be used in a very complementary way along with FFR. I also think that the technology folks will come up with better tools to combine these forms of imaging.”
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Technology integration
They already have, and in the process are helping to drive the curve for PCI optimization. For example, one new system integrates OCT and FFR to offer the advantages of FFR along with a side-by-side view of OCT and angiography via co-registration to map culprit lesions and provide the visual data needed to guide stent selection and deployment. Another combines IVUS and FFR software.
“My gut tells me that [PCI] reimbursement will be predicated on the notion that if you don’t have a good reason to put a stent in, you’re not going to get paid,” insists Kern. “And the fact is, interventionalists now have the ability to document that very easily.” He cites advances in optical fiber pressure technology and microcatheters, as well as emerging tools to measure absolute blood flow through saline infusion.
As Kern sees it, though, the biggest development could well be outside the cath lab, in the field of FFR-CT. Here, the principles of computational fluid dynamics—widely used in the aerospace and automotive industries—are being deployed to analyze CT imaging data in order to assess the hemodynamic significance of coronary artery lesions. One product uses data from a standard CT scan to create a “personalized” 3D model of coronary arteries that analyzes the impact blockages have on blood flow.
Reaching the next level
What could further alter the landscape for adoption of these tools is a rating upgrade from the American College of Cardiology. Currently, FFR and IVUS carry a Class IIa recommendation (though a Class Ia from the European Society of Cardiology). “FFR is already validated and I think in the next two years we’ll see it bumped up to a Class Ia for assessment of intermediate lesions,” predicts Pothineni. “And that will definitely increase the number of procedures being performed.” As for IVUS, Kern believes the missing link in the march toward greater hospital usage is additional data from large-scale outcomes studies now pending.
He’s just as adamant, though, that any discussion over which tool might gain a competitive edge misses a more important point. “The modern interventional cardiologist should employ these tools as appropriate for the data they have at hand, and use them clinically for situations where they need help and more information,” he maintains. “And if they’re not using them, I think they should reconsider their career choice.”