|William F. Fearon, MD, interventional cardiology and assistant professor at Stanford. Image Source: Stanford University|
The FAME study, which made headway in fractional flow reserve (FFR) validation last year when results were presented at the TCT meeting, is again in the spotlight with its publication in the Jan. 15 issue of the New England Journal of Medicine. Some analysts believe more studies are needed to further validate FFR, an index for functional severity of coronary stenosis, however, FAME co-principal investigator William F. Fearon, MD, disagrees.
“I don’t think FFR needs to be validated anymore. There are many studies published prior to FAME that have validated FFR in a variety of scenarios and have suggested that FFR’s routine use in people who have multivessel disease is beneficial and cost-effective. What FAME does is confirm these earlier studies,” said Fearon, a cardiologist in the division of cardiovascular medicine at Stanford University Medical Center in California.
“It’s always nice to have more data, but this is the best data we can ask for: a large—more than 1,000 patients—international, multicenter, prospective, randomized trial,” he said.
FFR is a catheter-guided procedure performed during angiography that measures the blood pressure and flow through a specific part of the coronary artery. In the FAME trial, researchers randomized patients to either FFR-guided PCI or angiography-guided PCI. The benchmark cutoff value for a positive FFR finding is <0.75, but the FAME investigators used <0.80. An FFR of 0.80 or above signified good flow and no accompanying ischemia. Any lesion with an FFR value below the threshold was stented.
FAME (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation) results showed that patients whose PCI was guided by FFR received significantly fewer stents and less contrast material, thereby having lower costs associated with their procedure; had shorter hospital stays and significantly lower incidence of major adverse cardiac events (MACE).
Some commentators have suggested that the FAME results would not be reproducible in a routine clinical setting but Fearon disagrees. “FFR is not a very complex method,” he said. “It involves standard techniques that all interventional cardiologists have mastered.”
He said that understanding some of the nuances of FFR requires some education, but one doesn’t need a “two-week training course.” In fact, he said that most interventional cardiologists could master the nuances after performing about 10 cases.
Using FFR is even easier since GE Healthcare partnered with Radi Medical Systems last year to integrate wireless FFR into the cath lab (FAME investigators used the Certus pressure wire from Radi.) Traditionally, FFR equipment had to be wheeled into the cath lab and cables needed to be hooked up, which “met with resistance from staff,” said Jim Archetto, president of Radi, which was recently purchased by St. Jude Medical.
With the partnership, FFR capabilities will be available on GE’s Mac-Lab IT hemodynamic recording system. About half of the interventional labs in the U.S. have FFR capability, with either the Radi or Volcano pressure wires, Archetto said. While the growth of new business is encouraging, the penetration rate is low (about 10 percent), that is, the actual number of PCI cases where FFR is used. Radi expects the number to climb, given the FAME results and the strategic partnership with GE.
“Ease of use is critical,” Fearon said. “It makes a difference in the ability of the community interventional cardiologist to apply it.”
Fearon also is involved in research regarding the index of microcirculatory resistance (IMR), a new measure of microvasculature function using a pressure sensor/thermistor-tipped guidewire. He uses the Certus wire from Radi, whose sensor can act as a thermistor and measure temperature. By measuring the transit time of room temperature saline, interventionalists can estimate the flow through small vessels—vessels that are not well visualized on angiography and that “we do not have any good, easy way to assess in the cath lab.”
The status of small vessels is important, for example, in people experiencing a heart attack. The smaller vessels are often affected by the larger stenotic arteries. The IMR of those small vessels predicts outcomes, Fearon said. He and others are conducting studies to determine how predictive the IMR is and how it might impact physicians' ability