Patrice Wendling

May 18, 2017

PARIS, FRANCE — The first prospective study of a 2.0-mm drug-eluting stent (DES) met its primary end point and was associated with a reassuringly low rate of clinical events in patients with CAD in very small coronary vessels[1].

The 12-month target lesion failure rate was 5%, which met the performance target of 19% (P <0.001).

In addition, there was zero stent thrombosis with the investigational 2.0-mm zotarolimus-eluting stent (Resolute Onyx, Medtronic).

Dr Matthew J Price

"This dedicated size of Resolute Onyx allows for the successful treatment of lesions involving extremely small vessels, thereby fulfilling an important unmet clinical need," co–principal investigator Dr Matthew J Price (Scripps Clinic, La Jolla, CA) said here at EuroPCR 2017.

As reported by heartwire from Medscape, the Resolute Onyx recently received FDA approval for stent sizes up to 5.0 mm, but the 2.0 mm has not been cleared for use to date. The smallest-sized DES currently available in the US is 2.25 mm.

The mean reference vessel diameter (RVD) in the RESOLUTE ONYX 2.0 mm Clinical Study was 1.91 mm.

Patients with CAD in vessels <2.25 mm are currently managed with bare-metal stents, oversizing with a 2.25-mm DES, or plain old balloon angioplasty, as drug-eluting balloons are not yet available in the US.

Smaller preprocedural RVD is associated with increased target lesion revascularization and worse survival from major adverse cardiac events (MACE), even in the era of drug-eluting stents, Price said.

Dr David Holmes (Mayo Clinic, Rochester, MN), who comoderated the late-breaking clinical-trials session, agreed that "it's an incredibly important unmet clinical need" and expects the stent will earn FDA approval. But he said in an interview that use of the stent "will be pretty uncommon because in many 2-mm vessels it will be hard to document they have ischemia."

He continued, "This will be for patients that have more diffuse disease, maybe a long [left anterior descending artery] LAD. This isn't going to be for branch little tiny vessels. You're going to treat the main vessel, so I think the number of patients is going to be pretty small."

The multicenter study enrolled 101 patients with clinical evidence of ischemic heart disease with stable or unstable angina or ischemia and a single or two de novo coronary lesions in separate target vessels with a RVD from 2.0 mm to 2.25 mm, TIMI flow >2, and lesion length <27 mm.

The mean lesion length was 12.6 mm, mean patient age 67.3 years, and 46.5% of patients had diabetes mellitus.

During a discussion of the data, Price noted that "if there was anything more than a 50% lesion, I believe, in the target vessel, you needed a [fractional flow reserve measurement] FFR to prove that the area in question was actually ischemic to really make sure that we were not just putting small stents in small arteries that were not clinically meaningful."

A myocardial perfusion substudy, as-yet reported, is also looking at differences in preprocedural ischemia, he added.

Patients were treated postimplant with standard maintenance 75- to 325-mg daily aspirin indefinitely and an oral P2Y12 antagonist daily for at least 6 months and up to 12 months in patients not at high bleeding risk.

Rates of lesion, device, and procedure success were 99%, 96.2%, and 97% in the study, published in JACC: Cardiovascular Interventions.

At 12 months, the MACE rate was 5%, driven by 2% target lesion revascularization (TLR) and 3% target vessel MI. No cardiac deaths occurred.

Notably, rates of target lesion failure and TLR were similar in patients with and without diabetes.

An angiographic substudy in 26 patients at 13 months revealed an in-stent late loss of 0.26 mm, which is consistent with prior zotarolimus-eluting stents in larger-diameter vessels, Price said.

If there is a small glimmer of concern it was an in-segment percent diameter stenosis of 37.92 and in-stent binary restenosis rate of 12%. The latter is higher than what one would see in larger vessels, likely because there isn't much headroom for even small amounts of late loss when using a small stent in a small vessel, Price said in an interview.

What remains to be seen with longer follow-up is whether continued in-stent late loss and "disease that may progress in areas outside those small stents over time may cause problems," he added.

The study was supported by Medtronic. Price reports consulting for AstraZeneca, ACIST Medical, Boston Scientific, Medtronic, St Jude Medical, and the Medicines Company and receiving speaker's fees from AstraZeneca, Abbott Vascular, Medtronic, St Jude Medical, and the Medicines Company. Disclosures for the coauthors are listed in the paper. Holmes reports financial relationships for himself and his institution with Boston Scientific.

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org, follow us on Twitter and Facebook.

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