A routine role for intravascular imaging (IVI) guidance for percutaneous coronary intervention (PCI) has long been favored by many of the technology’s researchers and enthusiasts. Now evidence from large, randomized trials may be catching up with such aspirations, though not without caveats.
One way IVI guidance may achieve that, the research suggests, albeit more speculatively, is by cutting risk for stent thrombosis, compared with the risk associated with angiography-only PCI.
The new studies, two large randomized IVI trials plus a meta-analysis of 20 such studies, were presented at the annual congress of the European Society of Cardiology.
In one, called ILUMIEN-4, PCI guided by optical coherence tomography (OCT) was associated with fewer procedural complications and better acute results – that is, larger post-PCI minimum stent area (MSA) – than in angiography-only procedures (P < .001). Poststenting MSA, an established predictor of clinical outcomes, was the primary imaging endpoint of the trial with almost 2,500 patients.
Yet the OCT group’s greater post-PCI MSA did not translate to reduced risk for the primary clinical endpoint of 2-year target-vessel failure. Among secondary endpoints, however, stent thrombosis at some point during the follow-up was 64% less likely (P = .02) with OCT guidance than angiography-only PCI.
ILUMIEN-4, despite its neutral clinical result, still “strongly advocates” for PCI guidance by OCT, at least among patients like those in the trial, said principal investigator Ziad Ali, MD, DPhil. He based that largely on the strategy’s greater postprocedure lumen areas in the trials, which are among “the strongest independent predictors for long term outcomes,” said Dr. Ali, of St. Francis Hospital & Heart Center, Roslyn, N.Y., at a press conference on IVI trials during the ESC Congress.
Selected complex lesion type
In contrast, the OCTOBER trial, presented at the sessions back to back with ILUMIEN-4, saw OCT guidance lead to better clinical outcomes than angiography alone after PCI of bifurcation lesions, which normally can be a special challenge for operators.
In the trial, which entered about 1,200 patients with such complex lesions, the 2-year risk for major adverse cardiac events (MACE) fell 60% after OCT-guided PCI, compared with angiography-only procedures (P = .035).
The finding is novel for showing that OCT guidance in bifurcation PCI can make a significant clinical difference, said OCTOBER investigator Niels R. Holm, MD, at the same media presentation on IVI trials.
“Multiple studies have shown that OCT allows for optimization of bifurcation PCI, and our results confirm that such optimization may improve the patient’s prognosis,” said Dr. Holm of Aarhus (Denmark) University Hospital.
ILUMIEN-4 and OCTOBER, both of which prespecified the Xience (Abbott) everolimus-eluting stent for the procedures, were published in the New England Journal of Medicine in tandem with their respective presentations at the ESC sessions.
Covering the spectrum
A meta-analysis presented at the same ESC session compared IVI using either OCT or intravascular ultrasound (IVUS) with angiography-only PCI across 20 randomized trials with a total of more than 12,000 patients.
Significant outcomes for IVI guidance versus angiography alone included a 31% drop in risk for target-lesion failure, the primary endpoint. And this study, as well, showed a steep 52% reduction in risk for in-stent thrombosis with the IVI-guided approach.
Dr. Gregg W. Stone
And “for the first time” in IVI studies, “we demonstrated reductions in all-myocardial-infarction and all-cause death, the latter by 25%,” Gregg Stone, MD, Icahn School of Medicine at Mount Sinai, New York, said in presenting the meta-analysis. Dr. Stone is also the ILUMIEN-4 study chairperson.
“The routine use of OCT or IVUS to guide most PCI procedures will substantially improve patient event-free survival,” he predicted, “enhancing both the long-term safety and effectiveness of the procedure.”
Dr. Stone said that IVI guidance “should be standard of care, if not in all patients, then in most patients.” Part of the rationale: PCI is unlikely to be improved much further by incremental gains in drug-eluting stent design. “That technology has almost plateaued.” But there’s yet room for “substantially improved outcomes” from adjunctive treatments and techniques such as IVI guidance.
The 20 studies in the meta-analysis encompassed an array of patients and lesions both complex and noncomplex, Dr. Stone observed, including bifurcation lesions, chronic total occlusions, left-main coronary stenoses, and MI culprit lesions.
“They really covered the spectrum of PCI,” he said. “I’m not recommending that intravascular imaging be used in every single case. But I do think it should be used in the majority of patients” and be standard of care for PCI in left-main lesions and “complex coronary disease, high-risk patients, and high-risk lesions.”
Unique advantage
The IVI-guidance groups in both ILUMIEN-4 and the meta-analysis showed a significant drop in risk for stent thrombosis – that is, abrupt thrombotic vessel closure, which typically occurs in 1% or fewer PCI cases but can trigger an MI and pose a mortality risk up to 45%.
Those risk reductions are consistent with a unique IVI advantage: the ability to guide optimization of stent deployments. When formally presenting ILUMIEN-4 at the ESC sessions, Ali observed that IVUS and OCT imaging allows operators to identify and often correct less-than-ideal results of an initial stent delivery – such as residual gaps between stent struts and vessel wall – that may encroach on the lumen, with possible clinical consequences.
Such imaging, said Dr. Ali, “lets you identify tissue protrusions, malappositions, dissections, and untreated reference-segment disease” that may potentially trigger thrombosis. That makes a strong argument for giving IVI guidance a more common, perhaps even routine role in PCI procedures.
Selling routine IVI-guided PCI in practice
“I think the study results are quite clear,” said Deepak L. Bhatt, MD, MPH, as session comoderator following the OCTOBER presentation. “The challenge, though, will be convincing the average interventional cardiologist worldwide that it was specifically the imaging and not the extra care that the patient getting OCT also inherently receives.”
Dr. Deepak L. Bhatt
Did OCT’s better trial outcomes stem from IVI itself or from greater operator attentiveness to procedural results – such as, for example, more high-pressure expansions to optimize stent placement, “the sort of thing that tends to occur when invasive imaging is added on to just plain old angiography?” Dr. Bhatt asked of Lene N. Andreasen, MD, who had just presented the OCTOBER trial. “There’s no way of uncoupling the two things.”
What can be said, “at this point, to convince interventional cardiologists that the extra time, energy, expense, is truly indicated,” that the data are “sufficient to change global practice?” asked Dr. Bhatt, Mount Sinai Hospital and Icahn School of Medicine at Mount Sinai.
That remains an open question,” acknowledged Dr. Andreasen of Aarhus University Hospital. The best argument in favor of selective IVI-guided PCI is that “we actually see a clinical benefit” in the trials. “But of course, it comes with a cost. It comes with longer procedures and more contrast.” How clinical practice responds to the new data remains to be seen, she proposed.