Intravascular Imaging in PCI: Time for a Guideline Update?

Robert A. Byrne, MB BCh, PhD; Rasha Al-Lamee, MBBS, MA, PhD


September 13, 2023

Recorded August 28, 2023. This transcript has been edited for clarity.

Robert A. Byrne, MB BCh, PhD: Hello and welcome. My name is Robert Byrne. I'm a cardiologist working in Dublin, Ireland. I'm very pleased to be here at ESC 2023 in Amsterdam. I'm delighted to be joined by a friend and colleague, Rasha Al-Lamee.

Rasha Al-Lamee, MBBS, MA, PhD: Hi, Rob.

ILUMIEN IV: OCT vs Angiography

Byrne: Rasha is from London in the UK. We're here today to discuss some interesting clinical trial data that have become available at the meeting.

Rasha, there was a huge number of high-profile randomized clinical trials presented here. I lost count of the number of papers that were in The New England Journal of Medicine, but I think I stopped somewhere around eight. A couple of these dealt with intravascular imaging, two in particular, and we're going to discuss these two together with a third study that was presented in the same session.

Why don't we start with ILUMIEN IV?

Al-Lamee: We were all waiting for the results of this trial. In fact, this was a really hard trial to do. The investigators have to really be commended for getting this trial done and getting it done over a very difficult period during the pandemic.

They recruited 2487 patients internationally and randomized patients to angiography-guided percutaneous coronary intervention (PCI) vs optical coherence tomography (OCT)–guided PCI. The patients they recruited were what they deemed to be either high-risk patients, patients with diabetes, or those with high-risk lesions — predominantly, these were long lesions, but they could have been other complex lesions, such as bifurcations or chronic total occlusions.

They looked at two major endpoints. The first was a procedural endpoint, which was minimum stent area, which we know to be the biggest predictor of stent failure in our patients. The second was a clinical endpoint, which was target vessel failure. Interestingly, they showed, as we might have expected, that the OCT-guided arm had much larger stents at the end of the procedure. However, they didn't meet the endpoint in terms of target vessel failure. There was no difference between the two arms.

Byrne: Interesting and, I suppose in some respects, disappointing because we've waited a long time for this trial and maybe we were expecting a clear result. How do we square the circle? They did find a significant difference in terms of minimum stent area, which is a strong predictor, as you said, of adverse events during subsequent follow-up, but they didn't find a difference in terms of outcome events over the time period of the follow-up.

Al-Lamee: The investigators gave us some plausible possibilities for why that happened. One was that, over COVID, they saw that the event rates in the trial fell, and that was possibly because patients weren't presenting to hospital, particularly with chest pain that might have triggered urgent revascularization events. Importantly, they did show us that, during the procedure itself, the OCT arm had much lower rates of significant procedural complications. There was some value to doing the OCT.

I think where the study, for me, is most interesting is the strategy that they used for OCT. That was very much based on this minimal lumen diameter (MLD) max criteria, where you would take a patient and not just perform OCT at the point you most feel you need it in a procedure, but do it in a very systematic, sequential fashion, which is pre-PCI, to try and work out exactly what you're going to do in terms of strategy; mid-PCI, if you're trying to work out whether calcium modification techniques would make a difference; and then at the end, to look at the final OCT results. In the angiography arm, they did a blinded OCT so that they could obviously work out this minimum stent area endpoint.

I think the other part of the trial that was very important was that it was a blinded trial. Although obviously within the cath lab, everyone knew what had happened, outside of that cath lab, the patients and all of the subsequent medical teams and research teams had no idea whether the patient was in the OCT or the angiography arm. That, I think, is key. As you know, it's dear to my heart to think about blinded trials in this way.

Byrne: One of the things that people wondered about in advance was this relatively blind adherence — blind in a different sense, but adherence to a sizing protocol. Would that lead to an increase in perforations? Was there any signal in that respect?

Al-Lamee: The signal was very much that it was safer to use OCT, and actually, that they reduced major procedural complications by using the OCT. In fact, doing the imaging makes you, hopefully, size your balloons correctly and size your stents correctly.

OCTOBER: OCT vs Angiography in Bifurcations

Byrne: I suppose the devil is often in the details, and sometimes the protocols or how the intravascular imaging is implemented and how it's specifically used to guide operators can make a big difference.

Why don't we move on? The next trial up we had in the same session was OCTOBER — again, a trial that we'd been looking forward to very much. Do you want to tell us a little bit about that trial and what you made of it?

Al-Lamee: With the OCTOBER trial, there were some similarities in terms of trial design. It was smaller, with 1201 patients. What they did was take bifurcation lesions. They aimed to have predominantly left main lesions, but about 20% of the lesions ended up being left main bifurcation lesions.

They took patients and randomized them, once again, to OCT-guided vs angiography-guided PCI, with a similar approach to pre-PCI OCT, and then OCT following the stent, and then rewiring of a side branch, and then again at the end to look at the final result. Here, they had a major adverse cardiac events (MACE) endpoint and showed that the MACE events were very much lower in the OCT arm than the angiography-alone arm.

Byrne: I think the important thing is, of course, when you use MACE, you have to dig down and look at the individual constituent endpoints. I think we saw pretty concordant results across the individual composites of the primary endpoint.

Al-Lamee: Absolutely. The only thing I think is important to remember here is this time it was unblinded. You can always allude to maybe knowing that someone was in the OCT arm or the angiography arm might slightly change their care. It's hard to know.

Byrne: I think it's an important trial with a clear result. As to why there was relative underrepresentation of left main stem interventions, there are some obvious explanations, but what were your thoughts on that? Is it the reluctance of operators to use OCT in the left main stem, blood clearance, etc., or do you think there were other explanations?

Al-Lamee: I wouldn't ever consider doing left main PCI now without intravascular imaging. I do wonder whether the trial investigators, of whom probably many are imaging enthusiasts, might have been reluctant to take those really complex left mains into a trial, where they might potentially get an angiography-guided approach. It's hard to tell for sure.

Byrne: I think that's a very important consideration and a well-made point in relation to OCT vs intravascular ultrasound (IVUS) in the left main stem. I suppose we have more and more experience with doing OCT. Certainly, the more traditional approach is to use IVUS in the left main stem area for a variety of reasons. That's not a question that was addressed by OCTOBER.


It leads us to the next trial in the session, the third trial, which was the OCTIVUS trial, comparing directly two intravascular imaging modalities. Do you want to tell us a little bit about that?

Al-Lamee: This was really an OCT vs IVUS trial. They were looking for noninferiority on a MACE endpoint between the two. Indeed, that's exactly what we saw — that the two techniques were very similar in terms of the clinical endpoints. That's very important, I think. For many labs, there's the opportunity to use OCT or IVUS, and then there are some labs where only one is an option.

What we have here from OCTIVUS is the ability to say that the two are probably relatively similar. Of course, you have to consider the contrast burden to OCT and the learning curve of knowing one technique or the other. For investigators, it's about being comfortable with at least one technique and then applying that as much as you can, particularly in these high-risk patient and lesion subsets.

Byrne: We've seen a general increase in the usage of intravascular imaging over the course of the past 5-10 years in Europe and the United States. Historically, we lagged behind in comparison with our colleagues in Asia and East Asia, in particular. Of course, there was a large number of randomized trials already, looking at intravascular imaging guidance compared with angiographic guidance and showing benefit. One might observe that many of these were in East Asian populations.

After this meeting, we certainly have a broader spectrum of data available to us. I'll tell you that, in the acute coronary syndrome (ACS) guidelines (which were also presented at this meeting, at a session I was pleased to co-chair together with Borja Ibanez), we discussed intravascular imaging at length. There were some concerns regarding external validity of the available randomized controlled trials and the broad generalizability of the results. Now, we have more data available, which we knew were going to be upcoming. What's your opinion? Where are we now with intravascular imaging?

Al-Lamee: I'm really an enthusiast for imaging. I think once you learn these techniques and you start to apply them in your clinical practice, you see that although there is some upfront cost to using the catheter, you minimize complications in the lab and hopefully improve outcomes in the long term. I would like to see the guidelines change, and I think it's probably time to upgrade the indication for intravascular imaging, particularly in these higher-risk patient and lesion subsets, which form the vast majority of the kind of PCI that we're doing in our labs.

It's pretty common to have diabetic patients, longer lesions, or bifurcation lesions. I'd like to see it go to class IA. I hope that the guideline committees will start to think about that. I think we now have a real wealth of evidence telling us that most of the trials are pointing in very, very similar directions, and I think it will hopefully improve clinical outcomes if we start to see greater adoption of these techniques worldwide.

Byrne: I think the key aspect of the point you made then relates to selection of patient and lesion characteristics. One of the concerns that some would express is, by having a class I designation, are we saying that it has to be done in all lesion subtypes? But probably it's more in the high-risk subtypes rather than all lesion subtypes?

Al-Lamee: In my lab, my IVUS or OCT use — but predominantly IVUS for me, because that was where I've really been able to develop my expertise — is somewhere around 90%. I certainly am using it as much as possible. The only times I don't use it, if I'm honest, is if the patient has cardiogenic shock — so the cases where you're trying to get in and out and completely revascularize as much as possible in a very, very sick patient. Sometimes there are parameters that stop you being able to get out your intravascular imaging tool, but otherwise, I use it in the vast majority.

Having said that, I think there's a cost implication and a time application to that. If we really want to see the bang for our buck, we've got to be aiming at probably those higher-risk patients and lesions, from the point of view of a guideline committee. For most of our colleagues out there, especially those fellows in training, they're probably learning to use it more and more in most of the PCI that they do.

Byrne: Yes. I think so. We've seen generally increased experience across most centers. You can see, if you track any of the national data, large increases in use, which are prompted by randomized trial data that have become available. I know in terms of guideline committee discussions, there's much discussion between class IIA and class I, and already it was a very close-run thing and the decision was to wait and see what came from the randomized trials that are available now. They'll need to be digested.

Of course, we had hoped for a positive result from ILUMIEN IV, which as you alluded to is the trial with probably the highest-quality metrics, and that didn't happen. We will have a meta-analysis. I think that's being revised now after the meeting to include the latest trials that are presented here. Although that won't solve all ills because the limitations of the individual trials will continue to be represented in the meta-analysis, I think it'll probably move us a step further along.

Al-Lamee: I think what we've got from this meeting, on this occasion and with these very big publications, is hopefully an iterative step and a very positive one for intravascular imaging. Also, as we discussed, we have some ideas on how we use it in the lab to the maximum benefit. I think all of this is going to be additive for us as physicians and also for our patients going forward.

Byrne: Thank you very much, Rasha, for sharing those interesting insights. It's been a very interesting ESC 2023 here in Amsterdam, and we appreciate very much your discussion of these important trials.

Al-Lamee: Thank you, Rob.

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