As previously reported on Angioplasty.Org, a new method for the functional measurement of intracoronary pressures and the severity of blockages has been developed by researchers at Imperial College in London. One of the main advantages of this new method, called Instant Wave-Free Ratio™ (iFR), is that, unlike standard fractional flow reserve (FFR), it does not require injection of a vasodilator drug, such as adenosine, to induce stress on the heart. The result is that the procedure is more comfortable for the patient and potentially useable in clinical scenarios where vasodilation is not feasible, such as acute coronary syndromes, infarctions, unstable patients, patients with breathing problems; it may also be somewhat quicker, easier to use, and more cost-effective.
Not that the current standard fractional flow reserve is time-consuming or expensive — these “non-objections” of money and time have been disproved by several studies. In fact, Dr. William Fearon, co-principal investigator for the recently published FAME 2 study, will be presenting at next month’s TCT meeting in Miami Beach on the cost-effectiveness data from FAME 2.
Back to iFR — the initial ADVISE study results (ADVISE stands for ADenosine Vasodilator Independent Stenosis Evaluation) were presented by Dr. Justin E. Davies at last year’s TCT and subsequently published in the Journal of the American College of Cardiology. The comprehensive results of the ADVISE Registry were recently presented at EuroPCR by Dr. Davies in May and have now been published online ahead of print in EuroIntervention, the official journal of EuroPCR and the European Association of Percutaneous Cardiovascular Interventions (EAPCI).
The concern about iFR is whether or not this new tool is as accurate as FFR. After all, if interventional cardiologists are going to be using functional measurement to make decisions about whether or not to place a stent, the tool being used needs to be as precise as possible. The accuracy of iFR and how well it tracks with FFR, which has been tested in thousands of patients, is the big question — and the ADVISE Registry provides some of the answers.
iFR, which is a proprietary technology of Volcano Corporation (NASDAQ: VOLC), currently is under development, not approved for sale in any markets, and is continuing to undergo validation studies. As reported in our coverage of the EuroPCR presentation, it generated much debate at that meeting, especially with the developers of FFR. So it is important for the field of functional measurement that the data from that presentation and the ADVISE Registry have now been published in a peer-reviewed journal.
As readers of Angioplasty.Org know, we’ve been advocates for the increased use of functional measurement for many years. After all, it seems to be a no-brainer to use a tool that is more accurate than angiography alone when making a decision as to whether or not to stent, or which blockage to stent if there are several. The original FAME study showed that stenting a non-ischemia-producing blockage led to worse outcomes and that, if FFR were used to guide PCI instead of angiography alone, outcomes were better and costs were lower. Additionally, the more recent FAME 2 study showed that not stenting an ischemia-producing blockage, relying on medical therapy alone, led to significantly increased hospitalizations for “urgent revascularization.”
It’s my opinion that the future of PCI is going to be increasingly tied to the concept of functional measurement, whether that is achieved via FFR, iFR or some other “FR” as yet unknown. Not only will outcomes be improved, but costs will be reduced — and that will be a driver as reimbursements and appropriate use criteria guidelines come into sync with the results of these studies. Not to mention the whole issue of “over-stenting”. I mean if an interventional cardiologist has a functional measurement that he or she can point to, indicating that stenting is appropriate, that goes a long way towards validating the procedure to both patient and payer.
For more information on functional measurement, visit Angioplasty.Org’s Intravascular Guidance Center. For more on the development of iFR, read our exclusive interview with Dr. Justin E. Davies.