PARIS – An atherectomy device already on the U.S. market for treating calcified lesions in peripheral arteries showed safety and efficacy for treating severely calcified coronary arteries in preparation for stenting in a pivotal, multicenter study with 443 patients.
"We believe that the orbital atherectomy system is a unique technology that appears to address an unmet need in this difficult-to-treat patient population," Dr. Jeffrey W. Chambers said at the annual meeting of the European Association of Percutaneous Cardiovascular Intervention.
Based on the data collected in the new study, Cardiovascular Systems, the company that markets the orbital atherectomy system (OAS) Diamondback 360° applied to the Food and Drug Administration in March for approval to add severe coronary artery calcification as an indication for the device. The device received FDA approval for treating peripheral arteries in 2007.
The study met its primary safety and efficacy endpoints "by a significant margin," said Dr. Chambers, director of the cardiac catheterization laboratory at the Metropolitan Heart and Vascular Institute of Allina Mercy Hospital in Minneapolis. OAS treatment resulted in a 10% rate of major adverse coronary events during 30 days following treatment, significantly less than the 17% prespecified performance goal. The procedural success rate of 89% also significantly surpassed the 82% prespecified efficacy performance goal.
"This study is very important and clinically relevant," commented Dr. William Wijns, codirector of the cardiovascular center at OLV Hospital in Aalst, Belgium, who cochaired the session where Dr. Chambers gave his report.
The ORBIT II (Evaluate the Safety and Efficacy of OAS in Treating Severely Calcified Coronary Lesions) trial enrolled 443 patients at 49 U.S. sites. All participants had severely calcified coronary lesions that were at least 15 mm long. The patients averaged 71 years old, and two-thirds were men. The mean lesion length was almost 19 mm, with an average stenosis rate of 84%.
Patients had a cumulative 7% rate of severe angiographic complications following OAS treatment, which included type C dissections, perforations, abrupt closures, or slow or no reflow. The only significant clinical factor associated with the occurrence of one of these complications was lesion length: The longer the lesion, the more likely a complication. The complication rates for OAS seen in this study were similar to or less than the rates reported from past studies of rotational atherectomy for treating coronary arteries, Dr. Chambers said.
Safety was defined as the combined rate of cardiac death, myocardial infarction, or need for target vessel or lesion revascularization during the 30 days after treatment. The most common of these adverse events was non–Q-wave myocardial infarction, which occurred in nearly 9% of patients. Procedural success was defined as successful stent delivery, which occurred in almost 98% of patients, minus the rate of major adverse coronary events during hospitalization.
ORBIT II’s original design called for comparing OAS with rotational atherectomy, but that plan was abandoned because rotational atherectomy devices are not approved for treating severely calcified lesions, Dr. Chambers said. "The FDA felt that no other devices do this," which led to the uncontrolled study design.
The OAS uses a special guide wire that allows direct crossing of "almost all lesions," he said. The system works by removing calcium to improve arterial compliance and allow full stent expansion; the goal of OAS treatment is not debulking or plaque removal, Dr. Chambers said. The microparticles produced during the procedure are "smaller than with rotational ablation," small enough to safely pass through capillaries.
"There is a relatively easy learning curve of a couple of cases if you have used rotational ablation," he said. "The device has a leading edge that guides you into the lesion, acting as a pathfinder. The OAS is designed to engage the hard components of plaque and flex the soft components out of the way."
The ORBIT II study was sponsored by Cardiovascular Systems, which markets the OAS. Dr. Chambers is a consultant to Cardiovascular Systems and Boston Scientific. Dr. Wijns said he has received honoraria and research grants from several drug and device companies, but he had no disclosures related to Cardiovascular Systems; he has received honoraria and research grants from Boston Scientific, which markets a rotational ablation device.
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