As an early adopter of fractional flow reserve (FFR) for the diagnosis of ischemia, my initial decision to transition from angiographic-guided treatment to physiologic-guided treatment was driven by a desire to ensure that we were treating lesions appropriately. Despite countless studies indicating the weakness of the angiogram, far too many operators still rely on it for treatment guidance. The coronary angiogram is limited and does not measure the extent to which a stenosis is restricting blood flow. Accordingly, a physiological assessment such as FFR, clarifies angiographic interpretation, resulting in improved diagnosis and ultimately, superior treatment decisions.
In addition to more accurately treating patients, we quickly realized cost benefits with the adoption of FFR resulting from elimination of unnecessary treatments and reduction in readmissions. And, with the recent introduction of the instant wave-free ratio (iFR) version of FFR, we are poised to realize greater savings due to the reduction in adenosine costs and improved patient experiences. That is making a huge impact at Memorial Regional Hospital in Hollywood, Fla., and has the potential for greater savings across the healthcare system with increased adoption of this practice.
Unfortunately, many interventional cardiologists are still making final decisions to stent a vessel based on angiographic results without taking into consideration physiologic parameters that are, in fact, objective and not subject to misinterpretation. In many cases, physicians are not aware of or trained to use new physiological assessment technologies. I find this concerning, because as medical professionals we should embrace new technologies like FFR and iFR that are game-changers. Unfortunately, clinician behavior and guidelines are changing slowly. We are, however, getting stronger support from the American College of Cardiology, American Heart Association and the European Society of Cardiology in pushing for greater objectivity in guidelines. This, coupled with ongoing focus on outcomes, will provide increased justification for diagnosis with physiological assessment and ultimately greater adoption.
I recommend doctors get familiar with FFR first, so they feel comfortable with the pressure wire and making decisions based not just on angiographic data, but in conjunction with physiologic data. And when proficient, they can move on to iFR.
iFR — Underlying Technology
The instant wave-free ratio is a logical follow-on to FFR. Also a physiological assessment, iFR determines whether a stenosis is causing a limitation of flow in coronary arteries with subsequent ischemia. Like FFR, iFR is performed with high fidelity pressure wires that are passed distal to the coronary stenosis. The enhancement over FFR obviates the need for adenosine, a step that can be time-consuming and costly (for cath labs that utilize infrequently) and is contraindicated in some patients.
iFR isolates a specific period in diastole known as the wave-free period. During this time, competing forces (waves) that affect coronary flow are quiescent, and pressure and flow (Pd and Pa) are linearly related as compared to all other periods in the cardiac cycle. Therefore, when a stenosis is flow limiting, Pd and Pa pressures over the wave-free period diverge, with iFR values below 0.9 suggesting flow restriction (normal value is 1.0). Theoretically, iFR can be calculated using a single heartbeat, but is typically averaged over five beats for normalization. iFR is measured at rest, without the need for pharmacological vasodilators or stressors.
FFR and iFR Work Together
FFR and iFR work together seamlessly on one system console, utilizing the same pressure wire and providing dual modality. With the introduction of iFR, interventional cardiologists now have more choices; and with the flip of a switch, the iFR modality provides a hyperemia-free measurement.
Our staff is well-versed in the protocols and initiation of these modalities. The addition of an FFR evaluation to an initial iFR assessment adds only 10-15 minutes to the overall procedure time. With everything prepped and set on the table, the consult goes very quickly; whether I choose to do iFR or FFR, we do not waste any time.
Implementing the Hybrid Approach
Initially I tested iFR myself for a two-week period. I ran FFR for every iFR test to verify what my colleagues were saying as well as what clinical studies were concluding about iFR. My independent conclusions agreed with the data — there was almost 100 percent correlation between the two indices.
Following the initial trial period we implemented the hybrid approach. For iFR measurements greater than 0.93, a deferral is warranted; measurements less than 0.86 are treated by revascularization. If iFR measurements fall within the “grey” zone (between 0.86 and 0.93), we give adenosine and conduct an FFR assessment. Using these benchmarks, we are able to spare at least 60 percent of our patients from vasodilator infusion.
When you introduce iFR at a facility, training is critical for rapid success. At our hospital, there were interventionalists that were initially frustrated because not all of the staff were comfortable with the technology. However, as we conducted more and more iFR/FFR procedures and the benefits increased, the interventionalists became our champions, so training makes a big difference. Like any new technology, you go through the process of understanding the why, then the how, and ultimately you become proficient and benefits accrue to the various stakeholders.
Improving PCI Decision Making
Costs Savings: FFR requires adenosine, which could be expensive in the IV form. With the advent of iFR, we are saving hospitals money by reducing the use of adenosine. Further, the ADVISE II study concluded the iFR hybrid approach is in agreement with FFR 94 percent of the time. So why not use something that will immediately save costs, with no degradation in diagnostic accuracy? Memorial Regional Hospital has experienced at least a 60 percent reduction in adenosine use with the adoption of iFR. As adoption increases in other hospitals, cost savings will accelerate.
Patient Experience: iFR has improved the patient experience. Invariably, adenosine has had some impact on the patient, ranging from tightness in the chest and/or shortness of breath, to potentially more harmful symptoms and contraindications. With iFR, those impacts are avoided and patient experiences improve.
Increased Diagnostic Flexibility: Without the need for adenosine, iFR affords greater diagnostic flexibility. For example, measuring pullbacks in different areas that I want to assess can be accomplished quickly and easily. I can pull back my wire and do the iFR measurements from vessel to vessel, and from distal to mid and mid to proximal within those vessels. That kind of capability is invaluable. As well, determining the impact of revascularization or stenting is likewise simpler with added value.
Transitioning to Physiological Assessment
It is rare when I opt not to perform a physiologic assessment. With its ease of use, improved accuracy, greater objectivity and significant reductions in inappropriate procedures, it is indefensible to forego this technology. If I have a significant lesion strongly correlating with stress tests, then I will go ahead and revascularize the indicated lesion. However, if the lesion is not absolutely correlating, then I do not hesitate to include an iFR/FFR evaluation.
The healthcare industry is still in the early stages of implementing physiological assessments as the most objective pathway to diagnose and treat significant lesions. Though FFR has been with us for about 15 years, we still have many doctors who have not had experience with FFR, and that could lead to poor treatment decisions and outcomes.
According to the International Survey on Interventional Strategy published in Circulation in October 2014, 71 percent of cardiologists who participated in the international Web survey used visual assessment only to assess intermediate stenosis over requesting FFR measurements, even when resources were not an obstacle and it was contrary to guidelines. Of those, only 53 percent of purely visual decisions were concordant with FFR. The evidence is clear — we must continue to promote and support transition from angiographic-based decisions to physiology-based decisions with FFR and iFR.
The American Medical Association (AMA) and the Society for Cardiac Angiography and Interventions (SCAI) are now recommending that iFR measurements are most appropriately coded using the FFR CPT codes with a -52 modifier appended to the existing FFR codes. The -52 modifier indicates to the payer that the service described by the FFR codes was reduced because administering pharmacologic stress is not required to obtain an iFR value.
We are fortunate to have technological advances such as iFR and FFR to aid in our decision-making, improve patient outcomes and even reduce healthcare costs. It is incumbent upon each of us to embrace these technologies and lead change within our organizations. The healthcare system will ultimately demand it through more stringent guidelines and reimbursements tied to patient satisfaction, improved outcomes and reductions in costly readmissions.
Editor's note: Juan A. Pastor-Cervantes, M.D., is medical director, cardiac catheterization lab at Memorial Regional Hospital in Hollywood, Fla. He was previously an interventional cardiologist and peripheral vascular interventionalist at the Cardiovascular Institute of the South, and also was an assistant professor of medicine in the division of cardiology at the University of Miami School of Medicine.