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WASHINGTON -- Optical coherence tomography (OCT) was as good as intravascular ultrasound (IVUS) or angiography for sizing stents but also picked up some complications that the other guidance technologies missed, the head-to-head randomized trial showed.

For the primary efficacy endpoint of post-procedural minimal stent area, OCT was noninferior to IVUS (median 5.79 vs 5.89 mm², P=0.001 for noninferiority), , of New York-Presbyterian/Columbia University Medical Center in New York City, reported at the opening late-breaking clinical trial session here at the Transcatheter Cardiovascular Therapeutics meeting. The study was also .

The post-procedural minimal stent area was numerically lower for angiography, at 5.49 mm², but the subsequent test of superiority showed nonsignificance for OCT against angiography (P=0.12) or IVUS (P=0.42).

Procedural major adverse cardiovascular events occurred in four (3%) of the 158 patients in the OCT group, one (1%) of the 146 in the IVUS group, and one (1%) of the 146 in the angiography group, with neither comparison being significant.

Despite missing on superiority with the higher-resolution imaging, the trial proved that protocolized OTC is more than just pretty pictures, Ali said.

"People thought OCT led to smaller stents," he told 番茄社区app in an interview. "We proved it is just as good as IVUS but also identifies these post-PCI stent complications that can't be detected by IVUS or angiography alone."

"This has really shown for first time that the superior resolution of OCT can lead to detection of post-PCI complications that may affect outcome," he added.

Those "provocative" secondary findings for OCT included:

• Greater minimum and mean stent expansion than angiography
• Greater acute procedural success than angiography, defined as greater than 90% expansion in both halves of the stent
• Fewer untreated major dissections vs IVUS (14% vs 26%, P=0.009)
• Fewer untreated edge dissections vs IVUS and angiography
• Less untreated major malapposition than either IVUS or angiography (11% vs 21%, P=0.02, and vs 31%, P<0.0001)

But the trial, which included 450 patients at 29 sites in eight countries, wasn't powered for clinical outcomes. A planned international follow-up trial, to enroll some 3,000 patients and dubbed ILUMIEN IV, will be powered for that comparison between OCT and angiography.

"This putative advantage has been speculated as a benefit for years, yet has not translated into any meaningful clinical result yet," noted an by , and , both of Royal North Shore Hospital in Sydney, calling OCT "still not ready for widespread use."

Hard clinical outcomes are going to be key to drive use, commented , of Christ Hospital in Cincinnati, as a press conference panel member.

Seeing fewer restenoses because of better lumen expansion would be very convincing, agreed , of Houston Methodist Hospital.

On the other hand, it's possible that seeing minute differences would lead to overtreatment, , of Scripps Clinic in La Jolla, Calif., cautioned during the panel discussion. Still, "imaging is really underutilized" for stenting, he said.

Nationwide, angiography remains the most common for percutaneous coronary intervention guidance. IVUS has grown to use in about 20% of procedures.

Ali called himself a believer in OCT technology, which he uses on more than 60% of his procedures. "It does all the math for you," he said. "It has angiographic coregistration, so you stent from normal to normal and ensure the stent is fully expanded with no guesswork."

But there were some downsides to OCT imaging guidance, including more frequent post-dilatation, larger maximum balloon size, and higher balloon pressure than with angiography, the greatest contrast media use of all three groups, and longer procedure duration versus angiography. Ali noted, though, that fluoroscopy times and radiation dose were similar.

Bhindi and Allahwala noted the potential negatives also include "disruption of plaques in vessels during imaging ... and the obvious extra cost to the patient, insurer, and health-care system."

Kereiakes agreed, "It's incremental cost without an uptick in reimbursement."

Teirstein, though, said that it wasn't a "deal-breaker" cost, and "if it gives you that clinical outcome, it's worth it."

The editorialists also pointed to a design issue in the trial, with use of OCT protocolized but not that of either other approach.

The OCT protocol specified measurement of the external elastic lamina at both proximal and distal reference segment, which was designed to achieve larger acute luminal gain and greater lesion coverage than IVUS or angiography alone.

"IVUS been used for the last 30 years without a standardized protocol and has been shown already to improve outcomes," Ali said. "So we wanted to have as real world a study as possible, and thereby decided not to enforce a strict protocol for IVUS or angiography."

Notably, though, operators in the study used the external elastic lamina measurement in an almost identical proportion of patients with OCT and IVUS, at about 70%.

It's impossible to know whether the operators adopted the protocol from OCT for IVUS during the course of the study or had already been using that procedure, Ali suggested. "No one has ever taught anyone to use IVUS."