ORBIT II: Atherectomy System Shows Positive Results in Calcified Lesions
PARIS, France—A novel atherectomy system designed to clear away hard plaque components may improve outcomes in patients with severely calcified coronary lesions compared with historical controls, according to findings presented Thursday, May 23 at EuroPCR 2013.
Data from the ORBIT II trial were initially presented March 9, 2013, at the American College of Cardiology/i2 Scientific Session in San Francisco, CA.
For the current analysis, researchers led by Jeff Chambers, MD, of the Metropolitan Heart and Vascular Institute (Minneapolis, MN), reported updated data on the Diamondback 360ᴼ orbital atherectomy system (Cardiovascular System, St. Paul, MN).
Diamond Crown ‘Sands Away’ Hard Plaque
The Diamondback system uses a rotating, eccentric diamond-coated crown to “sand away” the hard components of plaque, leaving the soft components of plaque and tissue untouched.
In ORBIT II, 443 patients with severely calcified coronary lesions received treatment with the Diamondback system at 49 US sites. Almost all subjects (98.2%) also had stents, either DES or BMS.
There was a 7.2% rate of severe angiographic complications, including type C-F dissection (3.4%), perforation (1.8%), slow flow/persistent no reflow (0.9%), and abrupt closure (1.8%). Factors associated with angiographic complications included lesion length (OR 1.04; 95% CI 1.00-1.08; P = 0.0298) and, to a lesser extent, the highest deployment pressure during stent procedure (OR 1.16; 95% CI 0.99-1.35; P = 0.0710) as well as length of calcium (OR 1.02; 95% CI 1.00-1.04; P = 0.0717).
The in-hospital mortality rate in ORBIT II (0.2%) compares well with the 1.6% and 1.7% rates achieved in 2 previous studies of rotational atherectomy with or without stenting for severely calcified lesions: Clavijo et al (Catheterization & Cardiovasc Interv. 2006;68:873-878) and Abdel-Wahab et al (JACC Cardiovasc Interv. 2013;6:10-9). The 30-day mortality rate in ORBIT II (0.2%) also is lower than that seen in the previous studies (1.5% and 2.6%, respectively).
Meanwhile, the rate of non-Q-wave MI defined as CKMB > 3xULN was 8.8% in ORBIT II, which compares well with rates of the same endpoint from the study by Clavijo et al. When non-Q-wave MI was defined as CKMB > 20% of total CK, the rate was 1.4% in ORBIT II, much lower than the rates of 8.0% to 20.9% found in a previous trial investigating BMS in patients with severely calcified lesions by Mosseri et al (Cardiovascular Revascularization Med. 2005;6:147-153).
As reported previously, the primary safety endpoint of freedom from MACE (CK-MB > 3 times ULN, TVR, cardiac death) at 30 days was 89.8%, exceeding the performance goal of 83% (95% CI 87% to 92.7%). Individual component endpoints were:
- MI: 9.7% (non Q-wave 8.8%, Q-wave 0.9%)
- TVR: 0.7%
- TLR: 0.7%
- Cardiac death: 0.2%
The primary efficacy endpoint of procedural success was 89.1%, exceeding the performance goal of 82% (95% CI 85.8% to 91.8%). Individual component endpoints were:
- Successful stent delivery: 97.7%
- Less than 50% residual stenosis: 98.6%
- In-hospital MACE: 9.5%
- MI: 9.3%
- TVR: 0.7%
- Cardiac death: 0.2%
“The improvement in clinical outcomes might be attributed to the unique mechanism of action of [the orbital atherectomy system],” Dr. Chambers said, adding that it is “a unique technology that appears to address an unmet need for this difficult to treat patient population.”
Session chair William Wijns, MD, PhD, of Cardiovascular Center Aalst (Aalst, Belgium), commented that the selection committee for EuroPCR “felt this trial was potentially very important and clinically relevant.”
ORBIT II Not Randomized for a Reason
Dr. Wijns also asked why ORBIT II was not a randomized trial comparing the Diamondback vs. the Rotablator rotational atherectomy system (Boston Scientific, Natick, MA).
Dr. Chambers responded that his group initially proposed to randomize against the Rotablator. “But FDA said no, because Rotablator is not approved for severely calcified lesions,” he explained.
In response to further questions from panel members, Dr. Chambers explained that the Diamondback system can treat a lumen roughly 1.5 to 1.75 times the size of the device.
“The 1.25-mm device can treat up to about a 1.75-mm lumen, which is really all you need to do to be able to remove the calcium,” he said. “It’s not really about debulking, it’s about changing compliance and allowing the stents to fully expand.”
“What’s the learning curve for someone who’s used to Rotablator?” Dr. Wijns asked. Operators accustomed to that device will be competent after “a couple of cases,” Dr. Chambers replied.
For ORBIT II, target vessel reference diameter was required to be between 2.5 mm and 4.0 mm, with a target lesion that did not exceed 40 mm in length. Target vessels were required to have TIMI 3 flow at baseline, and the target lesion had to have fluoroscopic or IVUS evidence of severe calcium deposit at the lesion site based on the protocol definition. Severe calcium was defined as radiopacities noted without cardiac motion before contrast injection, generally compromising both sides of the arterial lumen with calcium length of at least 15 mm extending at least partially into the target lesion or presence of ≥ 270˚ of calcium at 1 cross section via IVUS.
Chambers J. Pivotal trial to evaluate the safety and efficacy of the Diamondback 360ᴼ orbital atherectomy system in treating de novo severely calcified coronary lesions (ORBIT II). Presented at: EuroPCR; May 23, 2013; Paris, France.
- Dr. Chambers reports serving as a consultant for Cardiovascular Systems and on the clinical events committee for Boston Scientific.