Intravascular imaging improves PCI outcomes, but barriers to adoption remain
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Key takeaways:
- Data suggest intravascular imaging during PCI improves clinical outcomes compared with angiography.
- Despite that, many barriers remain to adoption of intravascular imaging.
New data presented at the European Society of Cardiology Congress indicate that use of intravascular imaging during PCI improves clinical outcomes, but the issue of adoption is complicated.
In the U.S., intravascular imaging — OCT or IVUS — is used in approximately 20% of PCI procedures to give operators a better idea of how to properly size and place a stent. Compared with using angiography alone, using intravascular imaging leads to fewer cases of complications such as malapposition and dissection, and is strongly associated with reduced risk for stent thrombosis.
At ESC, ILUMIEN IV, the largest trial of OCT vs. angiography, did not demonstrate that using OCT improved clinical outcomes, but the researchers attributed the lack of positive results to the COVID-19 pandemic, during which target vessel revascularization procedures, one of the components of the primary clinical outcome, dropped sharply. OCTOBER, a trial of OCT vs. angiography in patients with complex bifurcation lesions, showed OCT improved clinical outcomes in that population. OCTIVUS, a trial of OCT vs. IVUS, showed no difference in clinical outcomes between the two main forms of intravascular imaging. And a meta-analysis of OCT vs. IVUS vs. angiography showed that compared with angiography, intravascular imaging lowered risk for all clinical outcomes, including target lesion failure, all-cause mortality and MI, and that there was no difference in clinical outcomes between OCT and IVUS.
Cost is a major barrier to adoption of intravascular imaging and economic analyses from those trials have not yet been performed.
Ziad A. Ali, MD, DPhil, director of the DeMatteis Cardiovascular Institute at St. Francis Hospital and Heart Center in New York, who presented the ILUMIEN IV findings at ESC, spoke to Healio about why ILUMIEN IV makes a case for OCT despite the neutral clinical-outcome findings, impediments to adoption of intravascular imaging and how OCT compares to IVUS.
Healio: At ESC, you talked about how COVID-19 might have made an impact on why the clinical outcomes in ILUMIEN IV didn’t favor OCT. But they did favor it in OCTOBER. Is there a difference in patient population, or was the discrepancy entirely due to the pandemic?
Ali: ILUMIEN IV is the only global trial ever conducted in this space. It was not restricted to Northern Europe. So that may have something to do with it. Also, it depends on when you enroll your patients. If OCTOBER had enrolled most of their patients by the time that the COVID-19 pandemic started, that has a profoundly different impact. I do not know all the nuances of the OCTOBER data, so I can’t comment on exactly why they didn’t see the same outcomes we did.
I can only comment on our analysis, which showed very clearly that prior to the pandemic, with patients who had at least 1 year follow-up, our hazard ratio of 0.7 was exactly where we anticipated when we powered the study. In addition, the hazard ratios for every component of the endpoints favored OCT except for target lesion revascularization. Cardiac death and target vessel MI are not choices. You don’t choose to die or have a heart attack. They are events. However, you choose to get a revascularization. If you are at home and have chest pain, you choose to go to the doctor and you choose whether that angina is bad enough for you to have a procedure to fix it.
I was in New York during the pandemic. It was impossible to go to the doctor or the hospital. Nobody wanted to come in for a checkup. In fact, the number of reported heart attacks around the country dropped around 50% because people were so worried about getting the virus that they suffered their heart attack at home. As a scientist, that’s a biologically plausible explanation: A global pandemic impacts a patient’s choice on whether or not to seek medical attention. A patient with angina’s only choice was telehealth at the time, so they would get uptitrated on medical therapy. When that happened, they realized that their angina was not going to kill them, and as a result, they managed medically. What is interesting is that while the event rates for TVR dropped during the COVID-19 pandemic, they did not drop for cardiac death and stent thrombosis. Those events continued to accrue because they cannot be changed by choice. These are some of the interesting nuances that we are putting together.
Another unique aspect of ILUMIEN IV is that naturally we cannot power a study for stent thrombosis. Nobody can, because it’s such a low-frequency event. You would need 20,000 patients. Instead, we found we had a 64% reduction in stent thrombosis, of which 96% of those patients had a heart attack or died. What’s meaningful about that is that all the stuff we saw that was fixed by OCT — malapposition, tissue protrusions, dissection — it makes sense that if you leave them hanging around in the artery, that can lead to thrombosis. The OCT fixed those and the stent thrombosis didn’t happen. In fact, there was not a single stent thrombosis in the OCT arm after the first month. That is a very impressive safety feature.
All of our findings are biologically plausible. One of the unique things about our study is that unlike any other imaging study, we did a blinded OCT in the angiography arm. That blinded OCT in the angiography arm was what was able to show us that you leave all of these bad things behind in the artery by angiography. Previously, people guessed that we left a bunch of tissue behind, we had protrusion, etc. Now we quantified it, and those things can be directly equated to the reduction in stent thrombosis.
Healio: Given all of this, will there be enough impetus to convert more operators who don’t use intravascular imaging into using it?
Ali: From a glass half-full perspective, intravascular imaging has grown from 2013 to 2019 by 60%. That is pretty good. There are very few things in medicine that grow at that rate. People are listening. It is being adopted. So why is the glass half-empty? Because two things really drive physician behavior: fear and finance.
Let’s talk about fear. Fractional flow reserve use in 2011 was 11.4% of all PCI. In 2012, it was 40.1%. Only one thing happened in between: the implementation of the appropriate use criteria. The government basically said, if you don’t do an FFR when putting in stents that are not appropriate by the appropriate use criteria, you might not get paid and you might lose your privileges because you are doing inappropriate PCI. Everything changed overnight. Those types of things are what change people’s behavior.
The second aspect is finance. Physicians are reimbursed so little for PCI already and we have to accept that intravascular imaging increases the procedure duration. If an operator can save time and nobody is checking their work, and they can get away with not using intravascular imaging because the angiogram looks great, a lot of people are going to do that. Especially when you have an additive cost to the original PCI procedure. The cost-effectiveness data actually show that at 2 years, IVUS is cost-effective compared with angiography guidance, because you prevent all these events. And now we have 5-year data to show intravascular imaging improves outcomes. So if we re-analyze that data for cost effectiveness, you can extrapolate that there would be a cost savings. The problem is that budgets are on yearly basis and not on a 5-year basis. Medicare knows it will save this money over 5 years, but the private payers don’t want to go down that route because most people change their insurance every 3 years, so they will not make that money back.
Those are the big things that are stopping increased adoption. Could a class Ia recommendation in the guidelines improve that? I think it would, but I am not sure if it would change it dramatically. Is a [class] Ia recommendation deserved? If you have an intravascular imaging-guided procedure, you are 45% less likely to die. That’s driven by CV death. Even drug-eluting stents don’t save your life and they have a class I indication. That doesn’t make sense: Drug-eluting stents reduce restenosis; they don’t improve mortality. But they have a class Ia indication for chronic coronary syndromes and for ACS. Meanwhile, you have a modality that is used once at about $750 and it improves your mortality, reduces your target vessel MI, reduces your risk of restenosis and reduces your risk for stent thrombosis. There is some kind of disconnect here that has been difficult for me to understand. The guidelines committees are finally going to be put on the spot. How much more evidence do you need before you make it a class Ia recommendation?
Healio: For OCT vs. IVUS, is there a case for one over the other, or should it depend on what the operator is comfortable with?
Ali: There are five head-to-head trials of OCT vs. IVUS. All five show equivalence. None show benefit of one over the other. The network meta-analysis presented by Gregg W. Stone, MD, shows they are equivalent. I absolutely agree that most the evidence comes from IVUS, but that is just because it’s older. If you have a 5-year-old and a 10-year-old, you have more report cards for the 10-year-old. You have had more time to accrue data. We have about 3,000 patients’ worth of data for OCT vs. IVUS. I did a back-of-the-envelope study. Our total OCT data is about 6,000 patients. So I took the first 6,000 patients for IVUS, and the results are exactly the same. It’s just a matter of time that evidence continues to accrue.
We also have to have some common sense. These modalities do the same thing: They make the same measurements, they allow us to assess the artery and one has higher resolution than the other. How can that be a bad thing? Why is it bad to see more clearly? That is why I think the comparison of OCT to IVUS is sort of unfair. What I think we need to do as a field is focus on the utility of intravascular imaging, because the totality of data for these intravascular imaging modalities, just like the European consensus document shows, is so strong. It is a call to action to get the guideline committees to endorse it. I hope the totality of the data and the contribution of ILUMIEN IV push the field forward to do safer procedures for patients.
References:
- Ali ZA, et al. Hot Line 4.
- Andreasen LN, et al. Hot Line 4.
- Park DW, et al. Hot Line 4.
- Stone GW, et al. Hot Line 4. All presented at: European Society of Cardiology Congress; Aug. 25-28, 2023; Amsterdam (hybrid meeting).
- Ali ZA, et al. N Engl J Med. 2023;doi:10.1056/NEJMoa2305861.
- Holm NR, et al. N Engl J Med. 2023;doi:10.1056/NEJMoa2307770.
- Kang DY, et al. Circulation. 2023;doi:10.1161/CIRCULATIONAHA.123.066429.
For more information:
Ziad A. Ali, MD, DPhil, can be reached at ziad.ali@dcvi.org.
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