Paris – The first multicenter, prospective trial of a drug-eluting stent designed specifically to treat lesions in coronary vessels less than 2.25 mm in diameter showed excellent outcomes, with a 1-year target lesion failure rate of 5% for the Resolute Onyx 2.0 mm diameter zotarolimus-eluting stent.
This result in the pivotal trial easily surpassed the prespecified performance goal of a 19% target lesion failure rate,, reported at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.
Hemodynamically significant lesions in such small vessels are “not uncommon, particularly in diabetic patients,” Dr. Price said in an interview. Indeed, 47% of patients in the clinical trial had diabetes.
At present, the only ways to treat coronary disease in arteries having a reference vessel diameter less than 2.25 mm are off-label placement of an oversized stent, with its attendant risk of complications; standard balloon angioplasty, which entails a particularly high restenosis rate in this setting; or medical management, the cardiologist noted.
He presented a multicenter, prospective, open-label, single-arm trial of 101 patients with documented ischemia-producing obstructions in coronary arteries having a reference vessel diameter less than 2.25 mm, a lesion length less than 27 mm, and evidence of ischemia attributable to the lesion, typically via fractional flow reserve. The mean diameter by quantitative coronary angiography was 1.91 mm.
The primary endpoint was the rate of target lesion failure at 12 months, a composite comprising cardiac death, target vessel MI, or clinically driven target lesion revascularization. This endpoint occurred in 5% of patients. There was a 3% target vessel MI rate and a 2% target lesion revascularization rate. There were no cardiac deaths.
“Importantly, the stent thrombosis rate in these patients with extremely small vessels was zero,” the cardiologist emphasized.
The mean angiographic in-stent late lumen loss at 13 months was 0.26 mm, which Dr. Price characterized as “quite good.” The in-segment binary angiographic restenosis rate was 20%.
“That’s slightly higher than you would expect to see in vessels with larger reference diameters. I think that’s because of the lack of headroom. You have a very small vessel, and, even with a very small stent, even a small amount of late loss will give you a larger percent diameter restenosis over time,” he explained.
The 19% target lesion failure rate selected as a performance goal in the trial was set somewhat arbitrarily. It wasn’t possible to randomize patients to a comparator arm because there are no approved stents for vessels less than 2.25 mm in diameter. The 19% figure was arrived at in discussion with the Food and Drug Administration on the basis of similarity to the performance goal used in clinical trials to gain approval of 2.25-mm, drug-eluting stents. Because the Onyx 2.0-mm-diameter trial was developed in collaboration with the FDA and the stent aced its primary endpoint and showed excellent clinical outcomes, Dr. Price anticipates the device will readily gain regulatory approval. In April 2017, the FDA approved the Resolute Onyx in sizes of 2.25- to 5.0-mm diameter.
The study met with an enthusiastic reception.
“That was terrific. It’s clearly an incredibly important unmet clinical need,” commented session cochair, MD, of the Mayo Clinic in Rochester, Minn.
Assuming the stent is approved, how should interventionalists put it into practice? he asked.
Dr. Price replied that, first, it’s important to step back and ask if percutaneous coronary intervention of a particular lesion in a very small coronary artery is clinically indicated. The stent itself is readily manipulatable. It is a thin-strut device constructed of a single strand of a cobalt alloy with enhanced radiopacity.
Investigators in the trial used the standard approach to dual antiplatelet therapy – at least 6 months, with 12 months preferable.
The 20% in-segment binary restenosis rate at 13 months provides a clear message for interventionalists, he continued. “What this tells me is that, while this is a very good stent, we can’t forget to treat the patient aggressively with medical therapy to stop the progression of prediabetes, diabetes, and small vessel disease in addition to treating obstructive lesions with a small stent.”
Asked if the lack of headroom in these extra-small arteries warrants liberal use of intraprocedural imaging to make sure the stent is perfectly apposed, Dr. Price replied that he doesn’t think so. He noted that intravascular ultrasound and optical coherence tomography were seldom used in the trial, yet the results were reassuringly excellent.
The study results were published simultaneously with Dr. Price’s presentation (JACC Cardiovasc Interv. 2017 May 17.). The trial was sponsored by Medtronic. Dr. Price reported serving as a consultant and paid speaker on behalf of that company, as well as AstraZeneca, Boston Scientific, St. Jude Medical, and The Medicines Company.