New Technology

Use Your Own Wire When Measuring FFR: The Catheter-Based ACIST RXi Rapid Exchange FFR System

Cath Lab Digest talks with Ronald P. Caputo, MD, FACC, FSCAI, and Alan J. Simons, MD, FACC, FSCAI, FACP, Medical Director, St. Joseph’s Cardiac Catheterization Lab, St. Joseph’s Hospital Health Center, Syracuse, New York.

Cath Lab Digest talks with Ronald P. Caputo, MD, FACC, FSCAI, and Alan J. Simons, MD, FACC, FSCAI, FACP, Medical Director, St. Joseph’s Cardiac Catheterization Lab, St. Joseph’s Hospital Health Center, Syracuse, New York.

Disclosure: Dr. Caputo reports he is a consultant to ACIST, Medtronic, and Boston Scientific. Dr. Simons reports no conflicts of interest regarding the content herein.

Dr. Caputo can be contacted at Dr. Simons can be contacted at

I. Ronald P. Caputo, MD, FACC, FSCAI

Tell us about the cath lab at St. Joseph’s Hospital Health Center.

We are a large community hospital in an urban setting, with about 450 beds. We have 5 cath labs. In addition to coronary interventions, we also do carotid and peripheral interventions, along with transcatheter aortic valve replacements, performed in our hybrid room. We generally do between 4800 and 5100 procedures per year. Within that number, we do about 1800 to 1900 percutaneous coronary interventions. There are currently 6 full-time interventional cardiologists working at our facility.

How are you using fractional flow reserve?

We do a lot of fractional flow reserve (FFR), especially since the widespread application of appropriate use criteria. FFR has become part of our daily thought process. We have all types of fractional flow reserve systems in our lab. Two of our rooms are hardwired for one system and two are hardwired for another. Three months ago, we got the ACIST RXi Rapid Exchange system and it is now in all five rooms. We use FFR in approximately 18% of our procedures. For us, this percentage is a lot higher than just two or three years ago. The FAME and FAME 2 trial data, as well as the appropriate use criteria, were the drivers for our increased utilization of FFR. 

When doing FFR do you use bolus or continuous adenosine infusion?

When doing FFR, we generally use bolus adenosine rather than continuous intravenous (IV) adenosine infusion because it is quicker and easier. Probably IV infusion is the more “pure” way to measure FFR, but because we are focused on rapid turnover and move a pretty high volume, we have been utilizing bolus adenosine.

What has been the reaction to the ACIST RXi system?

We have had very ready uptake. Certainly, if you know how to do FFR, you can use the RXi system without any additional training. For the staff, there was zero learning curve. I would say it is probably my preferred FFR device. It is hardwired in every room now, which tells me that generally there is a favorable opinion in regard to the catheter system. I don’t have a breakdown yet; we will have to wait another quarter before I can see what our utilization is for the different FFR systems. 

How is the ACIST RXi system different from wire-based FFR technologies?

Now that we have started using the RXi system, there are some really nice features that have caught our eye. First of all, we like the fact that operators can use their own wire, which is helpful in crossing lesions and allowing us to continue on with an intervention without having to change out the wire. You always hate to lose wire position. It is one of those things we learn as fellows — don’t lose wire position. Sometimes your wire position has to be given up if you are using a wire-based FFR system in the instance of a pullback measurement or a wire change for intervention. The other thing I like is that you are able to do a pullback with the catheter-based RXi system. The Navvus MicroCatheter can be pulled back over the wire without losing the wire position to interrogate the entire artery, and you can feel very safe in doing so. FFR permits you to pick out the parts of the artery that are the most hemodynamically important to treat. We base our intervention on that measurement, and our preferred wire is down the whole time. There are also some workaday things that have been nice with the RXi system: it is very, very easy to set up. You just plug in the catheter. You don’t have to re-zero everything, you just have to equalize before you head from the guide down into the artery.

Can you share more detail on how the ACIST RXi system works?

Being familiar with a wire means you know how it is going to behave. It is very easy to manipulate and get your preferred wire where you want it. You leave the wire all the way down, in the distal vessel, and then slide the Navvus MicroCatheter over the wire to any point within the vessel in relation to the lesion, while the wire remains fixed in place. Slide the Navvus MicroCatheter back over the wire to any point in the artery. Once you have done your interrogation with FFR and you know where you want to treat the vessel, take the equipment you are going to use and just slide it down over the wire that is still in place. Most of the benefit comes from the fact that you do not have to re-cross the lesion. When you do FFR, sometimes it turns out that the lesion is actually tighter than it looks angiographically. If you are using a wire-based FFR system and have done a pullback and/or need to exchange for your own workhorse wire, then you have to re-cross that lesion. I am sure there are rare cases where an operator can’t get back down or injures the lesion area with a wire while trying to re-cross. It is rare, but still, just being able to leave the wire in place gives you a feeling of security. It definitely does save some time, too. 

Can you give an example of a scenario where the ACIST RXi FFR system would be advantageous?

Let’s say there are three areas of narrowing within an artery. You are not exactly sure whether to treat all three lesion areas. Is one worse than the other? Do they all need to be treated? You can pull back the Navvus MicroCatheter through the lesions you are worried about. You can quantify the pressure drop across the lesions, and then you know which lesions are significant. If a lesion is significant by FFR, you can treat it and, since your wire is still down, you can readily interrogate another lesion in the artery. You just bring the catheter down and do another FFR measurement. With the wire-based systems, the wire has to be pulled back, which means you are losing position in the artery. You are putting the wire down beyond the lesion, the wire is pulled back through the lesion, and after you are done with the measurement, if you do a pullback, the wire is gone. That is a problem. 

How does the RXi system translate for use with multi-vessel disease?

I do like to have my own wire in order to manipulate it from vessel to vessel to vessel. Several studies have shown now that a high percentage of cases that look like three-vessel disease angiographically are actually only one- or two-vessel significant disease. We will probably be doing more multi-vessel FFR in the future and you are obviously asking a lot more of the wire in these cases. If you can use your own wire, it is much easier. 

Do you think some of the resistance to FFR is related to some of the challenges you describe with the wire-based systems?

Yes, to a certain extent the need to change out wires and the loss of wire position creates some anxiety, and is associated with time and capital costs. Those are probably the main objections people would have.

Have you found any cost advantage to FFR use in general?

If there is any question as to whether the intervention should be done or not, or there is a lesion that you end up not stenting, that is a big cost savings to the system. Or, likewise, if there are two sequential lesions that maybe didn’t look so bad angiographically, but you do a pullback and treat with one long stent instead of two — in this scenario, you can also save some cost. 

As you have been using FFR, do you track how often you are correct visually when you assess a lesion?

That would be a fun thing to do. I haven’t done that yet. I think you are surprised sometimes. I would say 50% of the time I get an unexpected result. You just can’t tell. I did a case last week where there was a lesion in the LAD and a lesion in the right coronary. The right looked far worse than the LAD, but it was not a functionally significant stenosis, and I ended up treating the LAD, which did have a very low FFR. FFR definitely adds to our appropriate decision-making ability. If there is no functional data, such as electrocardiogram (EKG) changes, and there is no previous test pointing to where the ischemia might be, then you can make mistakes. FFR adds to the accuracy.

Is there any value in post intervention FFR measurement?

I do see value in doing it, especially if there are sequential lesions. Say you have a mid lesion and a proximal lesion. You treat the proximal lesion, but you are still wondering if the mid is functionally significant or going to affect outflow. I think it is very helpful in those situations. It is very rare that you would want to use intravascular ultrasound (IVUS) and FFR in the same case, because it is a cost issue, so if you are unsure whether the stent is perfectly expanded, you can put the FFR catheter back down and re-measure. I don’t do it in every case. Probably it would be optimal to do so, but generally, if I get a good stent result, I am not putting the catheter back down unless I have a question.

Any final thoughts?

The Navvus MicroCatheter is very sleek and I have never had a problem crossing the lesion with the catheter. People also have raised concerns about putting a catheter down the vessel that is bigger than a wire, wondering if the catheter would affect flow. Menon et al did a study that was presented last year at EuroPCR1 where they put a Volcano FloWire down and then the ACIST Navvus catheter over it. The flow was not significantly affected. So the catheter has been proven to be low-profile enough that it doesn’t affect the FFR measurement. The other issue is a phenomenon called pressure signal drift. When you put a wire-based FFR system wire down into the vessel, you are supposed to calibrate it to the pressure in the guiding catheter beforehand, so they are equal. You put the wire down and then pull it back to check for a discrepancy in the pressures. Any discrepancy is called drift, and there is some evidence that less drift might exist with use of a catheter-based system1, which would actually improve the accuracy and repeatability of the measurements. 

II. Alan J. Simons, MD, FACC, FSCAI

Can you tell us about your work at St. Joseph’s Hospital Health Center?

I have been in practice for 22 years and I am the medical director of the cath lab. We are a relatively high-volume cath lab in New York State. Our volume and mortality are published annually by the State Department of Health. We participate in the American College of Cardiology-National Cardiovascular Data Registry (ACC-NCDR) and the New York State Department of Health PCI Registry, as well as some other registries. St. Joseph’s Hospital Health Center became accredited through Accreditation for Cardiovascular Excellence (ACE) a year and a half ago.2-3


Yes, it was a big deal, because there are very few large-volume private hospitals that are accredited. It takes a fair amount of money and manpower hours. I started as the medical director in 2011. We initiated the process that year, and St. Joseph’s Hospital Health Center became accredited in 2013. Accreditation is what I would consider the standardization of the cath lab across the country, as determined by our industry. As we compare ourselves to other centers in a competitive market, accreditation is a great advantage, demonstrating that we have high quality and meet the standards for our industry. I presented our experience with accreditation at this year’s SCAI meeting in Las Vegas in May. It is a great thing for the hospital and a great thing for all of us. People may say that they are very good at something, but unless you can prove it, it doesn’t mean much. ACE accreditation means that we meet the standards for our industry.

Can you describe your approach to the use of fractional flow reserve?

New York State is different than most places, because on an annual basis, the Department of Health publishes appropriate use criteria for our PCIs, along with mortality, both for individual physicians and for hospitals. In 2011, we learned this was coming, and at that time, we made sure that everyone learned about appropriate use criteria and that we followed it closely. We started to use FFR much more frequently on those grey cases that were borderline. FAME data on FFR use was favorable, but now with FAME 2, it is even more favorable. Hopefully, the next appropriate use criteria will incorporate the value of FFR use. The last version was released in 2012. The benefit of FFR is that in an intermediate case, it allows the operator to take what would initially be an “inappropriate” case or at least an “uncertain” case, and make it “appropriate” by doing FFR. Of course, if the FFR is normal, the lesion that the operator may have initially considered significant and in need of intervention actually does not require intervention. The operator can feel fairly confident that the patient’s overall long-term risk is low. Appropriate use criteria are based on data that tell us “fix only those things that you need to fix” and it is with some difficulty that people accept that, but that is the way it is. 

Yet FFR offers justification for stenting when it is appropriate.

You are proving that you did the right thing. You have to do that now, because a procedure being deemed “inappropriate” has a bad connotation. Again, in New York State, individual physician information is in the newspaper every year with our names next to it: “Alan Simons did x number of inappropriate cases in 2013.” People read that and then they say, maybe I had an inappropriate case. You want to limit your exposure as best you can. The reality is that if FFR is negative, the data says that the lesion does not have to be stented.

Can you talk more about how appropriate use criteria and FFR intersect at your lab?

For intermediate cases that do not meet the current appropriate use criteria guidelines, we do FFR. There are two apps that are available through the Society for Cardiovascular Angiography and Interventions (SCAI), an appropriate use criteria app and a PCI risk adjustment app. Both are in use by all our physicians. During a case on an intermediate lesion, it is not uncommon for us to plug the case into the app and see where we are, and if the lesion is borderline, we usually do FFR. If it comes up negative, especially now with the recent FAME 2 data, medical therapy in these patients is just as good of an option, if not better. We use FFR the way it is supposed to be used, to evaluate intermediate lesions, and if the lesions are normal, no PCI is performed, and if the lesions are abnormal, then a PCI is performed. According to the ACC-NCDR registry, St. Joseph’s Hospital Health Center is a higher than the median user of FFR and IVUS, really for those cases that are unclear. In the NCDR, our facility is compared to similar, high-volume centers, of which there are only 16, because most high-volume places do not participate. FFR has become a regular, daily part of our procedures. 

How was the adoption of the ACIST RXi Rapid Exchange system?

 I don’t know if we were the first center, but we had the system right away. We already had FFR in all the rooms in various forms, whether wireless, table-based, or a rolling system. As soon as ACIST put in the RXi system, we started using it, and it has been going ever since. There is a very short learning curve and the device is so easy to use that it was quickly adapted and accepted by the staff and all the physicians.

What do you like about the ACIST RXi system?

Obviously, the big advantage is that we are able to use any wire of our choice, and once the wire is down, it is fairly easy to do the procedure. The disadvantage of the wire-based FFR systems is that we must use their wire. These system wires, once they are in, are a good rail to use for PCI, because the wires are fairly strong and give excellent support. The disadvantage is that you have to get the wire where you want it to go. Sometimes that is a challenge. 

There are also technical aspects that are easier with the ACIST catheter-based system. You turn it on and it is ready to go. There is not a lot of manipulating; it is a very small, almost iPad-type of device that sits on the end of the table. It is very user-friendly. Zeroing and using the device is simple, either at the beginning of the case or after the procedure. If you have already placed a stent and would like to re-evaluate it with FFR, it is also very simple to do. The Navvus MicroCatheter has a very low profile. Once the wire is in place, I have yet to do a case where I have not been able to cross with the catheter. It is a much more user-friendly device than the wire-based systems. 

Is there any time savings?

There is very little set up after turning it on in the morning and letting it boot up. If you are working in the same room all day, the RXi system is ready to go. In terms of the time per case, if you are struggling with a wire to get down the vessel, that is going to take longer, and unfortunately, that is what takes all the time. Once you get your wire down, then the rest of the procedure, for the most part, goes fairly well. 

Any translation into cost savings?

I don’t have any data, but I would say it is probably about the same cost to do FFR with the ACIST RXi system as with the wire-based systems. However, if we put the wire-based system down, and then we don’t like their wire once it is in and take it out, then there are some technical issues. We have already crossed the lesion once, and now we need to cross again. We have to open up a second wire. 

Would crossing with the second wire mean a greater risk to the patient?

Crossing with a second wire does increase the risk of the procedure, because the second wire could cause a dissection or some other issue. Although the likelihood of that happening is small, it is not zero. 

What do you think about doing post intervention FFR measurements?

I do it, because it is easy to do. Sometimes I am surprised and the FFR is not perfect when I am done. It doesn’t happen very often. I either post dilate a bit more or there is a new area I didn’t notice that needs to be addressed. With the ACIST system, it takes very little time to put the catheter down and measure FFR again. 

How do you envision the future of FFR?

It is going to take off, because it is now mandated that interventionalists prove that what we are doing is considered appropriate. There is going to be a huge increase across the entire country, for several reasons. First, everybody wants to follow the appropriate use criteria, and second, FFR is relatively easy to do with a catheter-based system. It is easier to do FFR than to do IVUS. FFR doesn’t replace IVUS, but if IVUS is being used to calculate area stenosis to see if there is a reason to treat the vessel, then FFR is a much quicker and easier procedure. 


  1. Menon M, Jaffe W, Webster M, for the ACCESS-NZ Investigators. Poster: FFR measurement using a new ultra-thin monorail catheter based system. EuroPCR 2013. Paris, France, 21–24 May 2013.
  2. St. Joseph’s Hospital Health Center attains triple accreditation status with Accreditation for Cardiovascular Excellence; ACE E3 symposium video to release this week. Cath Lab Digest. October 28, 2013. Available online at Accessed October 21, 2014.
  3. How ACE accreditation helped St. Joseph’s keep a competitive edge. Available online at Accessed October 22, 2014.