So here's what I'm supposed to be talking about. So physiology-guided PCR, we know this. It reduces unnecessary stents, improves outcome. We know this. There's a plethora of physiology options that are available in your cat lab menu. And you have coronary physiology that can play a vital role, especially in complex PCI, and integrating resting and hyperemic indices may be really helpful in this scenario. So optimal Y-based physiology, again, credit Dr. Kern for this, for this universe of ischemic clinical testing, but we'll focus on what's on the right side of this, where you have this huge, you know, different techniques. You have FFR, IFR, RFR, DFR, DPR, and we'll see the next slide that has all of these things. You have your basic concept is towards the left side, you have your hyperemic indices, which is your FFR. You have partial hyperemia, which is contrast PDPA, and then you have your resting indices or non-hyperemic indices, NHPRs that I'll refer to here, which are all on the right side of this screen. And then they exist as PDPA, which is a whole cycle, or different degrees of gating or lowest in the whole cardiac cycle, depending on what the definition is on the right side. And the cutoff for most of that is 0.89. So devices-wise, you have guide Y-based devices, isoresistive devices, the Abbott device and the Volcano device, and the optical device are the OptSense and the Boston Scientific Comet devices. Now, the microcapital-based technologies are the ASSIST-RXI. Remember, I'm supposed to talk about wire-based technologies. So in terms of guide Y-based technologies, these have the longest track record. The sensor is at the proximal end of the flexible tip. There's a thin membrane over the large base, and then that causes a membrane deformation which loads the crystals. And if you have Volcano, it's IFR. If you have Abbott, you have RFR, and it's wireless. Volcano has a cable. If you're doing optical, there's a membrane deflection between two that causes a phase difference between two light beams that then modulates the frequency of the signal, and then it's carried by optical fiber. So there's a lot less drift. It's unaffected by temperature or moisture. OptSense has the DPR, and Boston Scientific, the DFR. Okay? Microcapital-based techniques, very briefly, it is optical. It's run by the ASSIST-RXI catheter. The nice thing is you can use your favorite wire with this catheter. That's the biggest advantage. And you can also do pullbacks without losing your wire position. So that's a little plug for, please do pullbacks. So in terms of the summary of coronary physiology, NHPRs do not really need a stress agent such as adenosine. It is measured mostly in diacetyl. They're numerically similar. And remember, the choice may not really be yours to make because it is whatever system that's available in your lab that you have to be familiar with what NHPR that they have on that system. So let's talk a little bit about pullback. In terms of the theory of tandem lesions, you can come up with all of these complex pullback things that tandem lesions go with. If you have stenosis A and B, as you pull back from the two, stenosis A interacts with stenosis B if you just have two lesions. Now, obviously, if you have a long series of lesions, then you can see that it's not just that. In diffuse disease, you get a spread of FFR that comes across the whole lot of these lesions, and there's a lot more variability in terms of FFR in diffuse disease. So focal disease, you do a pullback. You have a nice little bump there in that purple line. That's your abnormal FFR. You do PCI. We all know this. We're good at this. Diffuse disease, you have this diffuse pullback across the whole length, usually a very long vessel like an LED. And then the question is, what do you then do? The answer may vary depending on the circumstance. And we can look at specific scenarios where you would do different things. But that is a complex scenario. So in terms of practical procedures, really getting down to the nuts and bolts, how do you assess tandem lesions or diffuse disease? You normalize at the guide tip or in the aorta, especially if you think that there's osteolesion. I think normalizing the aorta is going to be important. You wire both lesions or all of the lesions, go into the distal vessel, induce hyperemia if you're doing FFR. If you're not, then you measure your NHPR. Most of these have a button that you can say pullback. And you press the pullback button and slowly pull back to the guide. And then you check for drift. So typically, the FFR or the NHPR is above the cutoff. You say, OK, we're going to defer PCI. And assuming there's no drift, you're pretty much done at that point. If it is below, then you perform the pullback. And you actually look at, OK, what does this curve profile look like? If there's a nice step up, oh, that's helpful. Then you say, OK, I'm going to stent this largest pressure drop area that I can see. Now, a lot of modern systems have core registration. So it might even put dots there for you to see, ah, that's where it is. And that might help you. And if you, again, check, make sure you don't have drift. And then after, it's important to repeat it again and perform pullback and stent further lesions if you need to. And that ties into one of the other things I'll be talking about later, those PCI measurements. So one of the things we learned from the DEFINE trial, and we are going to learn similar stuff from the DEFINE GPS trial, I guess, which if and when it gets completed and if and when it comes out, is that about one in four to one in five patients leave your cat lab with an abnormal physiology at the end of their PCI. We're not talking about before the PCI. We're talking about after you have done your best. And you're like, wait a second. That's a problem. You know, one in four patients are going away with abnormal results. That's not good. So that's something that's not a great outcome. And then you think, OK, how about FFR? You know, I believe in FFR. I don't know. I don't believe in the diastolic stuff. Let's look at FFR. OK, same thing. Most recent FFR search registry, should be a huge registry, more than 1,000 patients. And they looked at this again. About 440 vessels ended up with abnormal FFRs after. And this was associated with MACE. So, you know, I realize I didn't do a great job on this slide. But if you can see the red line, it's actually those people who had post-PCI FFR of less than 0.90. And the blue line is more than 0.90. And you can see that these events were significant. It was MACE and cardiac mortality. Now, I grant this. This is registry, single site, all of that. But hey, the data is there. I mean, it does speak. It's a big number. So how do you integrate resting and hypodermic indices? This is where I'm going to get into controversial territory. And my co-panelists are going to slaughter me. But this will be fun. I will give you my approach, which this is how I do it, which is I engage. I administer nitroglycerin. I equalize or normalize, depending on what system I'm using. I do a quick 10 to 15 seconds for a drift check recording. And then a wire deletion, flush, wait a second, get my NHPR. If it's significant, you know, I do a quick pullback, proceed with PCI. If it's not significant, I consider hypodermia at this point, especially if I'm using, say, you know, IFR or RFR, one of these diastolic indices, especially if I'm at like 0.91, 0.92, especially if I know that the LV function of that patient is abnormal, especially if I know that there's issues with hemodynamics, I would consider FFR in that kind of scenario. I would generally prefer IV adenosine, but sometimes I see adenosine would do whatever works for the practice for your lab, and then pull back and check for drift. In conclusion, physiology-guided PCI improves unnecessary stents, improves outcome. There's a plethora of physiology options in the cath lab menu. And I think the important thing is, you know, if you use physiology and get into the habit of it, resting and hypodermic indices, whatever you're comfortable with, and you do it pre and post PCI, that's really the most helpful thing you can do for your patients. Thank you.

physiology-guided PCR

coronary physiology

FFR

stents

cat lab menu