For several years now, I’ve been advocating for expanded use of functional measurement, otherwise known as Fractional Flow Reserve (FFR), as a way of determining whether or not a blocked artery is actually causing ischemia. A new measurement, made possible by recent advances in computer technology, called iFR (instant wave-Free Ratio™) may provide the momentum that pushes this concept into mainstream cardiology.
A bit of history: the striking results of the FAME study were first presented three years ago at the 2008 TCT, and they showed that coronary stenting guided by FFR was more accurate and had better outcomes than stenting that was guided by angiography alone. FAME showed that when FFR was used to judge whether or not to stent, the number of stents was reduced by a third. And, oddly enough, the positive outcomes of the patients was increased by a third. In other words, placing a stent in a blockage that is not ischemic causes more harm than good.
Conversely, utilizing stents guided by FFR makes stenting one third more effective!
It’s a no-brainer really. Measure the blood flow across the blockage instead of looking at a shadow image (or, as Dr. Gary Mintz calls it, a “silhouette-o-gram”). What may look like a significant narrowing may in fact not be limiting blood flow. And vice-versa.
But, according to Dr. Neal S. Kleiman of the Methodist DeBakey Heart and Vascular Center in Houston, only 6% of U.S. patients undergoing angioplasty have their FFR measured (this was noted in the Sept. 13 issue of the Journal of the American College of Cardiology).
There are a number of reasons for this: many hospitals have not invested in the necessary equipment to measure FFR; there is a perception that FFR adds too much time to the procedure; standard FFR involves administering a vasodilator such as adenosine, which may affect patients negatively, or may even be contraindicated.
And then there is there BIG reason! As Dr. David J. Cohen, Director of Cardiovascular Research at Saint Luke’s Mid America Heart Institute, told me after his recent TCT presentation showing the clear cost-effectiveness of FFR:
Q: Why aren’t more cardiologists using FFR if it is more cost effective and has better outcomes?
Dr. Cohen: That will happen when doctors are paid the same not to do an angioplasty as they are to do one!
That certainly took me aback. Would a cardiologist really do what may be an unnecessary procedure just for the money? Well, certainly not any of the cardiologists I know and talk to. But given the recent spate of “unnecessary stenting” lawsuits and legal actions, I would have to think about this for a minute….
I did, and what was obvious to me was that, if a cardiologist could quote a number that would show a stent, angioplasty, PCI was warranted, then these controversies would disappear. And FFR provides such a number. Below .80 you should revascularize the patient. Above .80 it’s a question, but probably not.
This brings me to iFR, as described by Dr. Justin Davies in his interview with Angioplasty.Org. iFR is a faster and less invasive way of determining whether or not a blockage is ischemia-producing. It does not require adenosine infusion and it removes virtually all of the objections that a cardiologist may have to using functional measurement, rather than angiography alone.
Right now it’s only in the research phase and not yet approved for use, but its implications are clear: more appropriate stenting, better outcomes, less invasive measurement.