An in-depth look at the ORBIT II trial

by Payam Dehghani, MD, FACC, FSCAI

SAN DIEGO — Previous studies have shown that a high load of calcium in coronary arteries predicts an increased rate of major adverse cardiac events.

The Diamondback 360 Orbital Atherectomy System (Cardiovascular Systems Inc.) is an FDA-approved device designed to tackle severe calcific lesions. Unlike rotational atherectomy, this is an orbital atherectomy device that is advertised as easier to use, simpler to set up, and treats the entire lumen in antegrade and retrograde fashion.

Payam Dehgani

The prospective, multicenter ORBIT II trial evaluated this device with the primary safety endpoint of MACE and primary efficacy endpoint of procedural success. This non-ACS group consisted of mostly men (64%), of whom 36% had diabetes, 15% had history of CABG and drug-eluting stents were used in 88%. The target lesion had to have fluoroscopic or IVUS evidence of severe calcium.

As presented at the Society for Cardiovascular Angiography and Interventions Scientific Sessions, the trial demonstrated that the device was efficacious in successfully deploying stents in 98% of cases, with a notable MACE rate of 19.4% at 2 years mainly driven by MI. Cardiac death (4.3%) and target vessel revascularization (8.1%) were modest in this patient population. Interestingly, diabetes did not increase MACE risk. The investigators projected total possible cost offset/savings of $4,913 at 1 year.

It is timely that use of the atherectomy device should be revisited, as this is the first prospective atherectomy study in more than 20 years. The taste left in the mouths of most of us from previous atherectomy studies is that atherectomy devices are difficult to use, and although they may be associated with acute gain they are often associated with late loss. The ORBIT II trial provides a viable FDA-approved option for such lesions, but it was not designed to look at acute and chronic effects on vessel size.

The main limitation of this trial is the lack of a comparator arm. Therefore, it is difficult to put in context this high 2-year MACE rate of one in five. The investigators discussed historical cohorts of patients with significant calcium in the HORIZONS-AMI and ACUITY trials as a potential comparator, pointing out that the 1-year MACE was as high as 20% (compared with a MACE rate of 19% at 2 years in ORBIT II). However, this is likely an unfair comparison as that population was entirely patients with ACS.

Future directions

The question remains, next time you perform catheterization on a non-ACS patient with severe calcified lesions in the coronary arteries, what should you think about?

These patients have a high MACE rate, no matter whether or not you use an atherectomy device, and expect at least one in five to be back within 2 years.
There is a feasible, easy-to-use device that is FDA approved and has been shown to facilitate and enable stent implantation with impressive procedural success. However, the jury is still out as to whether you are lessening your patients’ chance of coming back for revascularization or a cardiac event.

What are your thoughts on the results of ORBIT II presented at SCAI 2015 and use of orbital atherectomy in general? Let us know by commenting on this Eye on Intervention blog.

Payam Dehghani, MD, FRCP(C), FACC, FSCAI, is a SCAI 2015-2017 Emerging Leader Mentorship fellow; an interventional cardiologist within the Regina Qu’Appelle Health Region; director of the Adults with Structural Heart Disease Clinic; clinical co-director of the Prairie Vascular Research Network; and assistant professor at the University of Saskatchewan, Canada.

Disclosure: Dehghani reports no relevant financial disclosures.