'Precision PCI' Shines in Small Trial, Lauds IVUS, OCT Imaging to Guide Stenting

November 01, 2016

WASHINGTON, DC — The largest randomized trial to directly compare coronary angiography with two kinds of intravascular imaging—one older, one newer—for guiding stent placement and expansion found that both imaging technologies were similarly more effective than standard angiography[1].

The trial with more than 400 patients showed that stenting guidance with the newer form of intravascular imaging, optical coherence tomography (OCT), and the older technology, intravascular ultrasound (IVUS), were noninferior to each other in terms of quality of stent expansion. That was defined by the achieved minimum stent area (MSA), a gauge of the final dimensions of the stent as measured by OCT after PCI in all three guided-stenting groups.

Both intravascular imaging technologies led to significantly better post-PCI MSA compared with standard angiography. They were on par with each other for the primary safety end point, development of procedure-related complications like dissection, wall perforation, thrombosis, or acute closure.

The comparable results for the two imaging technologies in the ILUMIEN 3: OPTIMIZE PCI trial, presented here at the TCT-16 conference, include the caveat that OCT was performed according to a prespecified "stent-optimization algorithm" at each of its 29 hospitals in eight countries, including the US, Japan, and much of Western Europe.

That protocol, which sought to position and expand stents optimally according to relative measures of the target segment's external elastic lamina (EEL), was designed to standardize how operators use OCT to deliver the stent in the best way for each lesion. But angiography and IVUS were less regimented in the trial, performed according to "local standard practice."

The trial was seen as successful to the extent that it justifies a larger study of OCT guidance in a larger population, with clinical end points. ILUMIEN 3 "is an intermediate step toward identifying patient [subgroups] who are most likely to benefit, and therefore ILUMIEN 4 will focus on those patients," said Dr Ziad A Ali (New York Presbyterian Hospital and Columbia University, NY) after presenting the trial here at the TCT sessions.

Ali was also first author on the trial's publication in the Lancet the same day of its TCT presentation.

New Era of PCI Optimization?

Dr Ziad Ali

He told heartwire from Medscape that "the time is right" for interventional cardiology to embrace intravascular imaging for guiding PCI, and he was bullish on the virtues of OCT, pointing to procedural and anatomic results in the trial that were superior with OCT vs either IVUS or angiography and that supposedly correlate with better post-PCI outcomes. Based on the post-PCI OCT the patients in all three groups received, there were significantly fewer "untreated edge dissections" (intimal dissection at the ends of the implanted stents) in the OCT-guidance group compared with both the IVUS and angiography groups, he pointed out.

Specifically, as Ali reported at the sessions, 20% of stent malappositions in the IVUS arm, as judged by post-PCI OCT, were missed by IVUS at the time of stent placement. And although the actual rates of post-PCI plaque or thrombus protrusion into the lumen were similar in all three groups, "IVUS missed 54% of plaque protrusions, including 13% of major plaque protrusions."

Postprocedural End Points, OCT vs IVUS vs Angiography in ILUMIEN 3: OPTIMIZE PCI

Postprocedural Results OCT (n=140) IVUS (n=135) Angiography (n=140) P, OCT vs IVUS P, OCT vs angiography
Minimum stent area (mm²) 5.79 5.89 5.49 0.42 0.12
Minimum stent expansion (%) 87.6 86.5 82.9 0.77 0.02
Major dissection (%) 14 26 19 0.009 0.25
Major malapposition (%) 11 21 31 0.02 <0·0001
Stents Are Now "Pretty Darned Good"

Ali expects the uptake of OCT guidance in practice to surpass IVUS uptake over the past generation. "IVUS has been used for 30 years, and I think it got a bit displaced in the entire PCI arena," Ali said. It came into its own at a time when the field was trying to strengthen PCI outcomes by improving the stents themselves, not how they were put into position.

"But we're past that point now. We're at the point at which the stents are pretty darned good. And to get an iterative benefit, we need to do PCI optimization," Ali said when interviewed. That means using imaging to tailor stent positioning and degree of expansion, among other things, to the characteristics of each lesion and patient.

ILUMIEN 3 is seen as a win for intravascular imaging in general over angiography for coronary stent placement, and Ali pointed to ways OCT, in particular, seemed to especially shine. But some don't see it as a substitute for IVUS; they see both as parts of the toolbox.

"In terms of garden-variety stent optimization, they're equivalent," Dr Gary S Mintz (Cardiovascular Research Foundation, New York, NY) said to heartwire about the relative value of OCT and IVUS. "Eighty percent to 90% of intravascular imaging is for routine stent optimization, and routine stent optimization can be done with either. It's really personal preference."

Although there are specific special cases where either OCT or IVUS would be preferred, up-and-coming interventionalists would do well to "pick one, and get good with it," said Mintz, one of the earliest pioneers of IVUS and a coauthor on the published ILUMIEN report, one of his numerous IVUS-themed publications.

Is Stent Optimization Enough?

"I think clinical outcomes are going to be the key," not as much correction of malapposition or similar procedural adjustments, Dr Dean J Kereiakes (Christ Hospital Heart and Vascular Center, Cincinnati, OH) said at a press briefing on ILUMIEN 3. The trial's findings, he said, are "not all that surprising. The resolution of OCT is far superior; the fact that they can see these sometimes very minute abnormalities, it's not surprising you can do that."

But, Kereiakes asked, do the costs associated with the procedure "translate into hard clinical outcomes? At the end of the day, that's what's going to drive use of the technology."

At the same venue, Dr David E Kandzari (Piedmont Heart Institute, Atlanta, GA) agreed on the importance of clinical outcomes. "The issue of translation of these imaging findings to clinical outcomes is imperative, because we already have a succession of new contemporary data that indicates that the application of any imaging, whether OCT or IVUS, translates into improved outcomes, specifically by achieving a larger stent diameter."

An editorial[2] accompanying the trial publication also urges perspective about its use of procedural criteria to compare strategies. "Use of potential surrogate measures of clinical outcomes (the primary measure and focus of this study) should be viewed with caution," write Drs Ravinay Bhindi and Usaid K Allahwala (Royal North Shore Hospital, Sydney, Australia).

"The notion of changing management by a strategy such as OCT because of its ability to detect suboptimal stent deployment is based on perceived issues or problems rather than real validated prospective clinical outcomes. This putative advantage has been speculated as a benefit for years, yet has not translated into any meaningful clinical result yet."

They continue, "Clearly, the issue of stent failure is multifactorial, and the possibility that a small increase in MSA could improve outcomes has to be placed in this context and viewed against the potential negatives, including disruption of plaques in vessels during imaging, patients having longer procedures with more contrast than with angiography alone, and the obvious extra cost to the patient, insurer, and healthcare system."

Use of Venerable IVUS Stuck at 15%

After the formal ILUMIEN 3 presentation, moderator Dr Gregg Stone (Cardiovascular Research Foundation, New York, NY) observed that even IVUS, which has been available for decades, isn't widely used. Even mounting evidence that IVUS-guidance of coronary DES placement leads to significant reduction in major adverse cardiac events "has not moved the field forward. IVUS use is around 15%, in the field."

So why hasn't IVUS-guided PCI caught on more? "I think some people feel frustrated with IVUS. I think that they've never really learned to interpret it well," according to Mintz. "I think that OCT has certain advantages in terms of interpretation, or at least the end user perceives that it's easier to interpret." So, many clinicians who haven't given IVUS a fair try have been looking to OCT for a better experience, he said.

There is also the issue of extra cost for imaging guidance of PCI, panelists at the media briefing pointed out; that applies to both IVUS and OCT, but there are differences in their financial and clinical costs.

He pointed out that OCT adds about 13 to 15 minutes more to a procedure and adds the cost and risk of contrast injection; the catheter system itself can cost about $700, Ali said, but that varies from center to center. "About 30 mL" of contrast was needed for OCT, whereas IVUS does not require contrast.

"But the reality is that there's also potentially a benefit, and there are randomized trials showing a benefit of imaging over angiography guidance, particularly for complex lesion subsets," observed Dr Ajay J Kirtane (New York-Presbyterian Hospital/Columbia University Medical Center, NY). "I think the key here is to figure out what that balance is."

The trial randomized 450 patients to PCI guided by OCT, IVUS, or angiography; post-PCI OCT was performed in 415 patients. As reported in the journal, they had at least one target lesion with an angiography-estimated reference vessel diameter of 2.25 to 3.50 mm and a length <40 mm; excluded were left main or ostial right coronary stenoses, bypass graft stenoses, chronic total occlusions, planned two-stent bifurcations, and in-stent restenosis.

Procedural End Points, OCT vs IVUS vs Angiography in ILUMIEN 3: OPTIMIZE PCI

Procedural Results OCT (n=158) IVUS (n=146) Angiography (n=146) P, OCT vs IVUS P, OCT vs angiography
Procedure time (min) 71.0 73.0 57.5 0.99 <0.0001
Fluoroscopy time (min) 16.0 16.0 13.0 0.74 0.11
Radiation dose (Gy) 1.34 1.20 1.16 0.87 0.39
Contrast volume (mL) 222 190 183 0.004 0.001

The most appropriate cases for imaging-optimized PCI, Ali said to heartwire , seem to be when there is decreased likelihood of achieving a large MSA. Such cases might include PCI in diabetics, who have increased restenosis risk; patients with end-stage renal disease or target vessels <3 mm in diameter; patients with prior stent thrombosis; those receiving bare-metal stents; and those with acute coronary syndrome, he said.

"Those are the types where we're looking at to see if we can further optimize [PCI] and provide a benefit," he said. Such cases are seen every day at most centers, so "any hospital anywhere should be able to use imaging to optimize PCI in those subsets of patients."

Mintz does not see OCT replacing IVUS; rather, he sees preferred roles for both in practice. For example, IVUS can be preferable when contrast injections are best avoided; that may include patients with renal dysfunction; chronic total occlusions ("injecting the contrast to do the imaging can extend the dissection"); aortal-ostial lesions; and large target vessels, due to limitations of light penetration in OCT imaging.

On the other hand, Mintz said, "IVUS is not very good at looking at thrombus. If you have a patient who presents with a non-ST-elevation MI, with no obvious culprit [lesion], or multiple potential culprits—and that's about 50% of the cases—being able to identify the thrombus accurately tells you where the culprit is."

St Jude Medical funded the trial. Ali discloses receiving grants from St Jude and personal fees from St Jude, Acist Medical, and Cardiovascular Systems for work unrelated to the current study. Mintz discloses receiving grants from St Jude during the conduct of the study and grants from St Jude, grants and personal fees from Boston Scientific and Volcano, and personal fees from Acis. Stone reports receiving consulting fees from Velomedix, Toray, Matrizyme, Miracor, TherOx, Reva, V-Wave, Vascular Dynamics, Ablative Solutions, Neovasc, and Medical Development Technologies; serving as a consultant on prasugrel patient litigation paid for by Lupin Pharmaceuticals; and holding equity, stock options, or both in the MedFocus family of funds, Guided Delivery Systems, Micardia, Vascular Nanotransfer Technologies, Cagent, Qool Therapeutics, Caliber Therapeutics, Aria, and the Biostar family of funds. Disclosures for the coauthors are listed in the article. Bhindi and Allahwala report no relevant financial relationships. Kereiakes reported that within the past year he or his spouse had received consultant fees or honoraria from or served on the speakers' bureau for Harvard Clinical Research Institute, Boston Scientific, Abbott Vascular, Micell Technologies, Sino Medical Sciences Technology, Caliber Therapeutics, and Svelte Medical Systems and had equity in Ablative Solutions. Kirtane reported that within the past year he or his spouse had received grant support or a research contract with Medtronic, Boston Scientific, Vascular Dynamics, St Jude Medical, Abiomed, Abbott Vascular, and Eli Lilly.

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