Author + information
- †Interventional Cardiology Unit, San Raffaele Scientific Institute, Milan, Italy
- ‡EMO-GVM Centro Cuore Columbus, Milan, Italy
- §Imperial College London, National Heart and Lung Institute, London, United Kingdom
- ↵∗Reprint requests and correspondence:
Dr. Antonio Colombo, EMO-GVM Centro Cuore Columbus, 48 Via M. Buonarroti, 20145 Milan, Italy.
In 1981, David Auth, a former University of Washington professor of electrical engineering, invented rotational atherectomy (RA): the “rotablator,” one of the longest-lived devices in the field of interventional cardiology. RA remains a useful niche device for the percutaneous treatment of complex lesions, usually as an adjunct to subsequent balloon angioplasty and intracoronary stent placement. Fourrier et al. (1) performed the first case of RA in human coronary arteries in 1988. Since then, RA has been a useful tool to treat heavily calcified, fibrotic lesions and those undilatable with balloon technology (2,3). Attempts to treat such lesions solely with balloon angioplasty and intracoronary stent placement often lead to incomplete stent deployment with adverse future outcomes (4). Rotablation use with subsequent drug-eluting stent (DES) implantation has been proven safe with acceptable 9-month target lesion revascularization (TLR) rates (∼10%) (5). In a nonrandomized comparison of heavily calcified lesions in which DES were delivered with or without the need of RA, similar TLR, Q-wave myocardial infarction, and mortality rates were observed between the 2 groups at 6 months (6). A randomized comparison of DES versus RA with subsequent DES in calcific lesions appears difficult to be executed as only moderate calcific lesions amenable to both treatment strategies would be included. Randomized studies on RA debulking and subsequent stenting versus isolated stenting for restenotic lesions have reported conflicting results (7-9). The ROSTER (Randomized Trial of Rotational Atherectomy Versus Balloon Angioplasty for Diffuse In-Stent Restenosis) trial (8) reported lower TLR rates among the RA group at 9 months, whereas the ARTIST trial (Angioplasty Versus Rotational Atherectomy for Treatment of Diffuse In-Stent Restenosis Trial) (9) demonstrated clinical superiority of a stenting-alone strategy. However, the poor performance of the RA in the ARTIST trial was attributed to underexpansion of the stents implanted because of the low inflation pressures suggested by the study protocol.
Three decades down the line, orbital atherectomy has emerged as a new tool specifically conceived to deal with calcific coronary stenoses. In the pilot ORBIT I (Safety and Feasibility of Orbital Atherectomy for the Treatment of Calcified Coronary Lesions) trial (10), the safety and performance of the orbital atherectomy system for de novo calcified lesions was tested in 50 patients, with promising results. The sequel study presented in this issue of JACC: Cardiovascular Interventions, the ORBIT II (Pivotal Trial to Evaluate the Safety and Efficacy of the Orbital Atherectomy System in Treating De Novo, Severely Calcified Coronary Lesions) trial (11) lays out the larger experience of orbital atherectomy in 443 subjects recruited in 49 U.S. sites. We are very attracted by the appearance of a new technology aimed to address calcified lesions. The vast majority of research efforts aiming to tackle calcific and fibrotic lesions focus on developing novel, low-profile stent platforms that could be delivered even in the hardest of lesions. However, the approach of stent implantation without appropriate lesion preparation may lead to suboptimal results even after high-pressure post-dilation. This strategy is not necessarily due to a “naive stent delivery attitude”; it represents the “interventionist's survival instinct” when dealing with difficult lesions. Delivering the stent at the lesion site is frequently considered a successful endpoint regardless of residual lumen diameter stenosis or presence of underexpansion.
The immediate question coming to mind is: “What is wrong with RA?” The answer to this question should stem from a randomized trial comparing head-to-head orbital atherectomy to RA. We entirely agree with the investigators that such a comparison is essential to demonstrate the incremental benefits of orbital over RA. Orbital has the following main differences from RA:
1. As a result of the burr being constructed from 3 helically wound wires (like a spring), the size of the cutting device can slightly vary according to the degree of compression.
2. The crown, which comes at a fixed 1.25-mm size, is eccentric in shape, and therefore, orbits rather than spins concentrically on the wire.
3. The orbital path of the device around the periphery of the lumen allows the burr to attack the plaque, in contrast with the burr of a rotational device, which remains in one place. In orbital atherectomy, a healthy, compliant tissue should flex away, whereas fibrotic calcific lesions would generate an opposing force, allowing differential sanding.
4. The operator can control the speed of rotation with the knowledge that a higher speed will create a deeper rotational cut by increasing lateral pressure.
5. Differential and incomplete contact of the ablating wires to the wall of the artery allows some blood flow, which flushes debris and facilitates cooling, minimizing the potential for ischemia and thermal trauma.
Both rotational and orbital atherectomy share the same limitation: the need for a specific dedicated guidewire.
The ORBIT II study evaluated the feasibility and performance of this new atherectomy device in calcific lesions in patients from a U.S. multicenter registry. First of all, it is important to bear in mind the difficulties relating to the accurate definition of “severely calcific lesions.” The investigators report some specific features in an attempt to standardize the inclusion criteria; nevertheless, readers should be aware of unresolved limitations. The defined “performance goals” based on historic controls extracted from RA literature are interesting, but have serious limitations, despite sophisticated statistical analysis. We should wait for a direct comparison between rotational and orbital atherectomy before making any definite conclusions.
In line with the dictum “safety first,” the primary safety endpoint of this study, defined as freedom from major adverse cardiac events at 30 days for >83% of patients, was met (major adverse cardiac event–free 30-day survival ∼90%). However, we are surprised by the primary efficacy endpoint thresholds (residual stenosis under 50%, first reported in a paper by MacIsaac et al.  in 1995) selected by the investigators, particularly when taking into account that the reported mean residual post-stent diameter stenosis was 5.8%. Future studies should use more contemporary post-stenting residual stenosis cutoffs.
The main findings of the large multicenter experience are:
• The device was able to cross the majority of the lesions in which the device was activated; only 2 lesions could not be crossed.
• Stents were successfully delivered in almost all of the lesions (98.2%) with good angiographic final results. The angiographic endpoint of residual lumen diameter stenosis appears not fully informative compared with the measurement of final lumen cross-sectional area using intravascular ultrasound.
• Complications such as periprocedural myocardial infarction occurred at rates expected for “generic lesions” and were lower compared with other reports utilizing RA in calcific lesions (2,12). Unique is the absence of slow-flow or no-reflow.
If the results presented in this registry are confirmed in real-life practice, we believe that percutaneous coronary interventions will gain an important momentum, thanks to a safe and effective tool designed to optimally prepare calcific and fibrotic lesions. Without question, these new devices (probably more to come) dedicated to dealing with tough lesions will become important companions of bioresorbable scaffolds, whose performance relies on adequate lesion preparation.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Colombo is a consultant for CID, Saluggia, Italy, and a minor shareholder of stock in Direct Flow, Santa Clara, California.
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