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iFR in the Cath Lab
Easy to use, significant time and cost savings over current modalities
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There is a saying that the best defense is a strong offense. It is time for hospitals and interventional cardiologists to proactively re-examine the appropriateness of their treatment protocols. In doing so here at Banner Health, we have found that outcomes have improved, costs have decreased and general risks have declined in a risk-averse sector of health care.
Early in 2011, the cardiac team at Banner Heart Hospital, a specialty hospital in Arizona, started looking at the appropriateness of PCI procedures in preparation for the rollout of new guidelines from the CMS. Our facility performs about 2,200 interventions and approximately 6,000 total procedures per year. We realized that noncompliance with CMS guidelines would have a significant effect on reimbursement.
Appropriate utilization of PCI is deservedly a national health care policy priority for the United States. Because PCI is both common and costly, appraisal of appropriateness is warranted. The initial appropriate use criteria (AUC) have broad implications for health care providers and patients, and will be used as the basis for indications, referral patterns, treatment options, physician education, shared decision-making and reimbursement for years to come.
With that backdrop, we examined our current protocols and leveraged new technologies to ensure appropriateness of treatments.
FFR: A Major Step to Ensure Appropriate Utilization
Before the introduction of physiologic measurements such as fractional flow reserve, we relied on angiograms to guide therapy. The significant limitations of coronary angiography for determination of lesion severity have been well documented.
Alphonse M. Ambrosia
The advent of FFR has meaningfully enhanced our ability to guide appropriateness of treatment, especially in intermediate lesions. The correlation of ischemia on stress testing with FFR values less than 0.75 has been established in numerous comparative studies with high sensitivity (88%), specificity (100%), positive predictive value (100%) and overall accuracy (93%). As we focused on appropriateness and documentation, our use of FFR during a 24-month period increased from 7% to 19%.
There are, however, a number of disadvantages to FFR, including increased procedural time, the cost of the adenosine required to increase flow and potential patient intolerance to the adenosine.
iFR: A Natural Evolution
Banner Health was very comfortable with FFR, so a new modality, instant wave-free ratio (the iFR Modality, Volcano Corp.) seemed to be a natural progression.
With increased benefits over FFR, including time and the reduced need for adenosine, the only question was: What if the iFR measurement doesn’t match with FFR? The operators wanted to know whether iFR was reliable. Consequently, as the cath lab director, I went to England to work with Justin Davies, MBBS, PhD, and the team at Imperial College London to learn about iFR and get their advice on incorporating it into our system.
The biggest advantage of using iFR is the elimination of adenosine. iFR is performed using high-fidelity pressure wires, the same wires used in FFR, which are passed distal to the coronary stenosis. iFR isolates a specific period in diastole, called the wave-free period, and uses the ratio of distal coronary pressure (Pd) to the pressure observed in the aorta (Pa) during this period. During this wave-free period in diastole, flow is highest and the competing forces (waves) that affect coronary flow are quiescent; meaning pressure and flow are linearly related as compared with during the rest of the cycle. When stenosis is flow-limiting, Pd and Pa pressures over the wave-free period diverge; a normal ratio is 1 and iFR values less than 0.9 suggest flow constriction.
With multiple studies completed on its viability, iFR has proven similar predictive accuracy to FFR in the determination of physiological significance of a lesion. The ADVISE and RESOLVE studies confirmed that iFR has a diagnostic accuracy of about 80%, which is comparable to FFR. The ADVISE II study reported that a hybrid iFR-FFR strategy resulted in a correct diagnosis in more than 90% of cases when compared with a strategy of FFR measurement in all lesions, and this strategy avoided the need to administer adenosine in two-thirds of patients.
Trial Experience
We initiated a 60-day trial starting in July 2014 to evaluate iFR at Banner Health. An iFR machine was installed at three facilities: Banner Heart Hospital, North Colorado Medical Center and Banner Good Samaritan. One operator was designated at each facility to conduct the iFR procedures. We proceeded cautiously, as we did not have the same clinical outcomes data with iFR that we had with FFR.
Three Methods of Implementation
We evaluated 90 patients and 114 lesions during 60 days across the three facilities. Each facility was able to adopt the technology in accordance with their comfort level. Banner Good Samaritan conducted iFR in parallel with FFR in every case to see how it correlated with FFR. For hospitals that are moderately comfortable with FFR, running a parallel strategy may make the most sense until proficiency and confidence grow.
At the other end of the spectrum, Banner Heart Hospital quickly adopted the hybrid algorithm. Using this methodology, an iFR measure is taken; a measurement greater than or equal to 0.93 may be deferred, whereas a measurement less than 0.86 should be treated by revascularization. Stenosis with iFR measurements between 0.86 and 0.93 is considered in the “grey zone,” requiring adenosine administration and an FFR assessment to guide therapy. For hospitals that are proficient with FFR, adopting the hybrid algorithm is warranted because it allows you to take initial measurements with iFR and utilize FFR only to make clinical decisions for cases in the grey zone.
North Colorado Medical Center implemented a blended strategy that leveraged the parallel approach for the first 10 or 15 cases and then transitioned to the hybrid approach for the remaining cases.
Results
All three strategies worked for the individual operators and enabled each hospital to become comfortable with iFR and its correlation to FFR. During the 60-day period across the three facilities, we recorded a 58% reduction in adenosine use and a decrease in procedure time.
At Banner Heart Hospital, which used the hybrid approach, we conducted 21 cases, 10 of which were multivessel, and treated 30 lesions. The average procedure time was 40.2 minutes, including an average fluoro of 8 minutes and average contrast of 132 cc. In the 10 multivessel cases, there was no increase in procedure time compared with a typical case. With the hybrid approach, 67% of cases were adenosine-free, which resulted in significant time and cost savings. As we migrate toward an iFR modality more exclusively, it is anticipated that Banner Heart Hospital will experience additional savings, and Banner Good Samaritan and North Colorado Medical Center will accrue substantially more savings — all while ensuring appropriateness.
Advantages of iFR
In our experience, we have observed several advantages of iFR, including:
- Reduction in procedure time. Since the 60-day trial, iFR was implemented at Banner Heart Hospital and is now routinely used. We have already observed a significant reduction in procedure times due to elimination of the need for adenosine in at least two-thirds of cases. For example, in a recent multivessel procedure with a left anterior descending artery (LAD) intervention, iFR was performed on two branches of the circumflex as well as the LAD, and then the LAD was stented. The total procedure time from stick to closure device was 50 minutes. Without iFR, the same case would have taken at least 70 minutes (a 40% increase).
- Impact on throughput. For the busy interventionalist, it is nice to be in the cath lab for a period of time and do several cases in a row, which reduces setup and transition times. However, that is not always the case with more rigid hospital scheduling. We found that using iFR provided us the ability to complete procedures in significantly less time than the standard 90-minute cath slots. As a result, Banner Heart Hospital adopted more fluid scheduling. So, if we are finished in 45 minutes we can immediately start on the next case. If I can do five physiologically guided cases in the time that it would normally take to do three or four under a strict schedule, then that is a win/win for the interventionalist and for the hospital.
- Adenosine cost reduction. Besides saving time and increasing throughput in the cath lab, this technique also was associated with significant savings in adenosine. For example, at Banner Heart Hospital, use of the hybrid iFR-FFR approach reduced the need for adenosine in physiology cases by 67%, which resulted in significant cost savings for the institution.
- Post-measurements using iFR. The ability to rapidly and easily take post-measurements was part of what drove my personal interest in iFR. I did a lot of post-measurements with FFR, which was cumbersome because we had to run another 3 minutes of adenosine, re-zero the wire and re-normalize. With iFR, I can do it quickly with the same wire as the intervention. By taking a pre- and post-iFR measurement, I have a comfort level that my intervention is complete, appropriate and I have made flow as normal as possible.
- Elimination of hemodynamic effects. Last but not least, there is concern about the hemodynamic effects of adenosine. I have had several patients now who have been worked up for transcatheter aortic valve replacement due to critical aortic stenosis and we have used iFR on those patients to determine whether they needed coronary intervention before the TAVR procedure. So, for that population in whom you are concerned about hypotension with adenosine — and therefore excluded from doing FFR — iFR is a great alternative.
Future Use
As the appropriateness of PCI procedures comes under increased scrutiny by the CMS, it is critical for hospitals to continue to explore additional means to ensure appropriate use and provide relevant documentation.
FFR and iFR are invaluable, proven technologies that enable clinicians to make appropriate treatment decisions on whether to medicate, stent, defer or refer to surgery. However, with greater ease of use, significant time and cost savings over current modalities and improved defenses against inappropriate treatments, iFR has the inside track and will likely become the physiologic diagnostic of choice for hospitals in the near future.