SAN DIEGO, CA — Long-term data with an orbital atherectomy device suggest that approximately one in five patients with severely calcified lesions undergoing PCI will experience a major adverse cardiac event (MACE) at 2 years[1].
While the raw numbers might appear high, Dr Jeffrey Chambers (Mercy Hospital, Minneapolis, MN) said the results of the ORBIT II study, which lacked a head-to-head comparator arm, are in line with historical controls. "We are handicapped by a lack of a comparator group," Chambers told heartwire from Medscape. "This severely calcified patient population is understudied, and we don't know a lot about it."
Presenting the data here at the Society for Cardiac Angiography and Interventions (SCAI) 2015 Scientific Sessions, Chambers pointed to a pooled analysis of the HORIZONS and ACUITY clinical trials. In that combined analysis, investigators examined the impact of coronary calcification on clinical outcomes after PCI in 6855 patients and reported a 1-year MACE rate of 19.9%, which is higher than what was observed in ORBIT II at 2 years.
The atherectomy device used in ORBIT II, known as the Diamondback 360 (Cardiovascular Systems, St Paul, MN), rotates and orbits in an antegrade and retrograde fashion to effectively "sand" the calcified plaque from the coronary artery. The purpose is to facilitate stent placement. The study, which enrolled patients from 49 US sites, did not include a comparator arm because there is no Food and Drug Administration (FDA)–approved percutaneous device for treating severely calcified coronary lesions.
In total, 443 patients were included in the trial, with 419 available for 2-year follow-up.
"There is a real clinical need," he told heartwire . "The outcomes of patients with severely calcified coronary lesions are much worse [than those of patients without calcification]. They are very difficult to treat, they are prone to dissection, you can't deliver a stent a lot of time, you use a lot of equipment, and the stents fall off occasionally. It can be a really complicated procedure, and a lot of time it can't even be done."
Overall, the MACE rate in ORBIT II was 19.4% at 2 years. The composite end point—which included cardiac death, target vessel revascularization (TVR), and MI—was driven primarily by non–Q-wave MIs. To heartwire , Chambers said they used a stringent definition of CK-MB elevation, defined as three times the upper limit of normal.
In terms of individual components of the primary end point, 4.3% of patients died from cardiac causes, while the TVR and MI rates were 8.1% and 9.7%, respectively. In an analysis comparing diabetic vs nondiabetic patients, the MACE rates, as well as individual components of the MACE end point, were similar between the two groups.
The researchers also analyzed projected costs of the atherectomy system in the first year against a Medicare population with severely calcified lesions undergoing PCI. Compared with the Medicare patients, the initial up-front costs of the atherectomy device/procedure would be offset by savings accrued from a shorter hospital length of stay. The initial hospital length of stay appears to be approximately 1 day less for patients treated with the device, mainly because of reduced complications. There also appeared to be less target lesion revascularization (TLR)/TVR in the first year, said Chambers.
While there is not a large body of evidence to compare outcomes in patients with severely calcified lesions, Chambers said there is an ongoing clinical study that will compare standard of care in patients undergoing PCI with mild, moderate, and severe calcification. That study will provide some evidence on clinical outcomes in these tough-to-treat patients, he said.
Speaking during the late-breaking clinical-trials session, moderator Dr Ted Bass (University of Florida, Jacksonville) said the goal of atherectomy is to "prepare a vessel to be stented." The current technologies available to physicians treating severely calcified lesions are difficult to use, but they have never been shown to improve long-term clinical outcomes, such as decreased TVR or TLR. In the ROTAXUS study, rotational atherectomy prior to the implantation of a drug-eluting stent failed to have any impact on in-stent late lumen loss in elderly patients with calcified lesions.
"I'm not sure this device is doing anything different from the other devices in terms of preparing the vessel to get to that end point [of being stented]," said Bass. "Am I wrong?"
In response, Chambers said rotational atherectomy devices, as well as the orbital atherectomy device, are both excellent in achieving solid acute clinical outcomes, meaning high rates of stent deliverability. Whether or not the new device alters rates of revascularization against current standards of care will not be known until randomized, controlled clinical trials are performed.
Chambers said the results from ORBIT II are "provocative" in that the TVR and TLR rates at 2 years were favorable when compared with other PCI trials including patients with calcified lesions.
"Rotational atherectomy follows the wire and creates a channel to deliver a stent," Chambers told heartwire . "Orbital atherectomy rotates and orbits, but it treats a larger portion of the artery. I think it does something to break up the calcium, and that potentially allows for larger stent expansion. It's your stent expansion that really translates in your good long-term result."
During the SCAI presentation, Dr Gregg Stone (Columbia University, New York), who comoderated the late-breaking clinical-trial session, said the limitation of ORBIT II remains the absence of a control arm. He pointed out that the MACE rate in HORIZONS/ACUITY might not be applicable because those trials included non-ST-segment-elevation (NTSE) acute coronary syndrome and STEMI patients (compared with stable coronary artery disease patients in ORBIT II).
ORBIT II was sponsored by Cardiovascular Systems. Chambers reports consulting fees/honoraria from Cardiovascular Systems. Bass and Stone have no relevant financial relationships.
Heartwire from Medscape © 2015 Medscape, LLC
Cite this: Questions Linger for Orbital Atherectomy in Calcified Lesions: ORBIT II - Medscape - May 08, 2015.
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