Initial Experience With GlideAssist to Facilitate Advancement of Orbital Atherectomy Prior to Plaque Modification of Severely Calcified Coronary Artery Lesions

Abstract: Objectives. We report our initial experience with GlideAssist (Cardiovascular Systems, Inc) to facilitate advancement of the orbital atherectomy crown prior to plaque modification of severely calcified coronary artery lesions. Background. Severe coronary artery calcification increases the complexity of percutaneous coronary intervention (PCI) and is also associated with worse clinical outcomes compared with PCI of non-calcified vessels. Orbital atherectomy is an effective tool to modify calcified plaque prior to stenting. However, advancement of the orbital atherectomy crown may be technically challenging due to complex coronary anatomy. Methods. From February 2018 to February 2019, GlideAssist was used in 13 patients at the University of California, Los Angeles Medical Center. The primary endpoint was the 30-day rate of major adverse cardiac and cerebrovascular events, which was the composite of death, myocardial infarction (MI), target-vessel revascularization (TVR), and stroke. Results. Reasons for use of GlideAssist included severe angulation/tortuosity (76.9%), ostial lesion (15.4%), and presence of previously implanted stent proximal to the calcified target lesion (7.7%). All patients who required GlideAssist had successful delivery of the crown to the calcified lesion. One patient experienced a major adverse cardiac and cerebrovascular event, which was due to periprocedural MI that was due to coronary dissection. The same patient experienced subacute stent thrombosis 13 days after the index PCI requiring TVR. No patient died or had a stroke. No other angiographic complication occurred. Conclusions. The GlideAssist function is a useful feature of the orbital atherectomy system to facilitate successful delivery of the crown in complex coronary anatomy. 

J INVASIVE CARDIOL 2019;31(11):331-334.

Key words: calcified coronary artery, orbital atherectomy, plaque modification 

Coronary artery calcification (CAC) represents a severe form of atherosclerosis. It is commonly present in patients who undergo coronary angiography, with a prevalence of 73% based upon intravascular ultrasound (IVUS) imaging.¹ CAC increases the complexity of percutaneous coronary intervention (PCI), as it can be difficult to advance balloons and stents. It can also be a barrier in achieving optimal stent expansion, which may explain the higher risk of ischemic complications, including death, myocardial infarction (MI), target-vessel revascularization (TVR), and stent thrombosis.^2,3 

Orbital atherectomy (Cardiovascular Systems, Inc [CSI]) modifies calcified plaque, which facilitates stent delivery and optimal stent expansion. In the pivotal ORBIT II trial, orbital atherectomy was safe and effective for the treatment of severely calcified coronary artery lesions at 30 days and 3 years.^4,5 Similarly, a multicenter, real-world registry reported the safety and efficacy of coronary orbital atherectomy at 30 days and 1 year.^6,7 

The presence of proximal vessel tortuosity and angulated coronary artery lesions can also increase the complexity of PCI. The risk of procedural failure and ischemic complications is increased by the following: vessel tortuosity, defined as the presence of two or more bends ≥75° proximal to the target lesion; at least one proximal bend ≥90°; or the presence of “significant” curvature proximal to the target and angulated (>45°-60°).^8-10 Such complex coronary anatomy can be a technical barrier for the use of orbital atherectomy, as it can be challenging to deliver the orbital atherectomy device to the lesion. 

The GlideAssist function was approved by the United States Food and Drug Administration on October 20, 2017 and was commercially available for orbital atherectomy devices in February 2018. The GlideAssist function, which spins at 5000 rpm, was designed to facilitate device tracking, removal, and smoother repositioning in challenging coronary anatomy. We prospectively evaluated our initial experience with the GlideAssist function to treat severely calcified coronary artery lesions in complex coronary anatomy. 

Methods

Study population. From February 2018 to February 2019, thirteen of the 43 cases treated with orbital atherectomy at the UCLA Medical Center in Los Angeles, California were facilitated by GlideAssist. Severe coronary artery calcification was defined as the presence of radio-opacities involving the vessel wall on fluoroscopy or ≥270° calcification present on intravascular imaging (IVUS or optical coherence tomography).⁶ The GlideAssist function was only used if the orbital atherectomy crown could not easily cross the lesion. The institutional review board approved the review of the data. 

Device description. Orbital atherectomy is an atheroablative device that facilitates stent delivery and expansion by modifying calcified plaque. The crown is 1.25 mm in diameter, coated with 30 micron diamonds, and eccentrically mounted. The crown rotates on a 0.014˝ ViperWire (CSI) and ablates bidirectionally while expanding laterally with centrifugal force. The ViperSlide lubricant (CSI) is continuously infused through the drive shaft to reduce the friction between the drive shaft and the ViperWire and cool the device to avoid thermal injury. GlideAssist is activated by continuously pressing the low-speed button until the green indicator light blinks, followed by pushing the power-on switch (Figure 1). 

Procedure and adjunctive pharmacotherapy. Standard techniques were used for PCI. Low-speed (80,000 rpm) atherectomy was used for all cases. High-speed (120,000 rpm) atherectomy was performed at the discretion of the operator if the reference vessel diameter was ≥3 mm for maximum plaque modification. The crown was advanced at a rate of 1 mm/s and limited to 20 seconds in each pass. Patients were preloaded with aspirin and P2Y₁₂ inhibitor prior to PCI. All patients underwent PCI with drug-eluting stenting unless patients were not candidates for prolonged dual-antiplatelet therapy. Unfractionated heparin was used in all cases.

Endpoints. The primary endpoint was major adverse cardiac and cerebrovascular event (MACCE), defined as a composite of death, MI, TVR, and stroke at 30 days. MI was defined as recurrent ischemic symptoms with new ST-segment elevation or re-elevation of cardiac biomarkers greater than twice the upper limit of normal. Target-vessel revascularization was defined as repeat revascularization of the target vessel. The diagnosis of stent thrombosis was adjudicated on the basis of the Academic Research Consortium definition.¹¹ Baseline clinical, procedural, and 30-day adverse events were entered into a dedicated PCI database. The secondary endpoints included angiographic success, defined as successful stent delivery with a residual stenosis <50% without angiographic complications including perforation, dissection, no reflow, and stent loss during the index procedure. 

Statistical analysis. Statistical analyses were performed with SAS Software System (SAS Institute). Continuous variables are presented as mean ± standard deviation, and categorical variables are presented as counts with percentages. 

Results

Baseline clinical characteristics. The mean age was 73.1 ± 11.2 years, and the majority of patients (69.2%) were men (Table 1). Diabetes mellitus was present in 38.5% and chronic kidney disease was present in 23.0%, with 7.7% requiring dialysis. The mean ejection fraction was 52.3 ± 12.8% and severe left ventricular dysfunction (ejection fraction ≤25%) was present in 7.7% of patients. 

Baseline angiographic and procedural characteristics. Reasons for use of GlideAssist included severe angulation/tortuosity (76.9%), ostial lesion (15.4%), and presence of previously implanted stent proximal to the calcified target lesion (7.7%). The orbital atherectomy device was successfully delivered and crossed the lesion in all 13 patients. The number of vessels treated per case was 1.2 ± 0.2 (Table 2). The number of stents used per case was 2.0 ± 1.1, and the mean stent length was 42.4 ± 26.8 mm. Drug-eluting stents were used in all 13 patients. The mean number of passes was 3.7 ± 1.9 per case, with high-speed atherectomy (120,000 rpm) used in 61.5% of cases. A transvenous pacemaker was not used in any case. A hemodynamic support device was used in 7.7% of cases.

30-day clinical outcomes. One patient experienced MACCE (7.7%), which was due to periprocedural MI caused by coronary dissection during treatment of an ostial right coronary artery stenosis (Table 3). The same patient experienced MI due to subacute stent thrombosis 13 days after the index PCI requiring TVR. No patient died or had a stroke. Successful stent delivery was achieved in all patients. Emergency coronary artery bypass graft surgery was performed in 0.2%. No other angiographic complications, including perforation or no reflow, occurred (Table 4). 

Discussion

GlideAssist was used to successfully deliver the orbital atherectomy crown in complex coronary lesions. The orbital atherectomy crown successfully crossed the lesion in all patients. One patient had MI due to coronary dissection and subacute stent thrombosis.   

Delivery of the orbital atherectomy crown may be difficult if the lesion location is in the distal segment or the vessel is tortuous and angulated. An example of challenging anatomy is a sigmoid-shaped right coronary artery, which makes delivery of the crown particularly challenging. Transradial access provides less guiding catheter support during PCI compared with transfemoral access, leading to the guide catheter “kicking out.” Several techniques can be implemented to facilitate delivery of the crown. Deep-seating of the guide catheter can be used to enhance support, but can increase the risk of coronary dissection. Larger diameter guide catheters (7 or 8 Fr) provide more stability and support. However, large-bore catheters increase the risk of vascular access-site complications like bleeding and pseudoaneurysm, especially if transfemoral intervention is used. An 8 Fr guide catheter is not used for transradial intervention, and a 7 Fr guide catheter is infrequently used unless a sheathless guide catheter is used. A mother-and-child catheter such as the GuideLiner (Vascular Solutions), which provides guide extension, can be used to facilitate the delivery of the crown; however, it increases the cost of the procedure and may increase the procedural time and risk of dissection. 

The treatment of calcified aorto-ostial coronary artery lesions with orbital atherectomy is technically challenging but feasible.¹² The orbital atherectomy crown can potentially damage the guide catheter if it is not adequately retracted from the ostium and if orbital atherectomy is activated while still inside the guide catheter. Excessive whipping of the orbital atherectomy crown could occur if the guide catheter is not sufficiently near the ostium to provide adequate support. One technique to successfully treat ostial lesions with orbital atherectomy is to initially traverse the ostial lesion using the GlideAssist function, followed by ablation at low speed in a retrograde fashion. 

One patient experienced MACCE due to periprocedural MI as a result of coronary dissection. This patient subsequently developed subacute stent thrombosis. Coronary angiography after the GlideAssist was used to traverse calcified plaque in the ostial right coronary artery revealed no coronary artery dissection. The first pass of the orbital atherectomy device was performed at low speed in a retrograde fashion. The patient underwent orbital atherectomy with 2 passes at low speed and 1 pass at high speed before the device was removed. The patient complained of chest pain and had ST-segment elevation on electrocardiogram after removal of the crown. Coronary angiography revealed a dissection that extended down to the distal segment. Whether the coronary dissection occurred during orbital atherectomy or due to guide-catheter dissection is unknown. The patient later presented to an outside hospital with acute ST-elevation MI due to stent thrombosis. Stent thrombosis was likely due to stent under-expansion, as intravascular ultrasound was not used to optimize results after the placement of 4 long drug-eluting stents. 

Rotational atherectomy (Boston Scientific) is another option to treat severely calcified coronary lesions. If the lesion is very tortuous or angulated, the rotational atherectomy burr can be advanced with the Dynaglide function. The Dynaglide speed typically is 60,000-90,000 rpm. In such complex coronary anatomy, a 1.25 mm burr is commonly chosen as it is easier to advance than a 1.5 mm burr. However, if the reference vessel diameter is ≥3 mm, a 1.25 mm burr may not be large enough to adequately modify the calcified lesion. Therefore, after initial passes with the 1.25 mm burr, the device requires removal, exchange to a 1.5 mm burr, and re-advancement to the calcified lesion, increasing the procedural and fluoroscopy times. A disadvantage of using rotational atherectomy is that it only ablates during antegrade advancement. Inadequate atheroablation during antegrade advancement with the 1.25 mm burr and the lack of diamond chips on the proximal half of the burr can lead to burr entrapment during retrograde movement.^13-15 Orbital atherectomy has diamond chips on the entire length of the crown and ablates bidirectionally, which makes crown entrapment less likely. There have been no reports of crown entrapment with orbital atherectomy. 

Another practical use of GlideAssist is to facilitate advancing the ViperWire. The ViperWire may inadvertently come back when advancing the orbital atherectomy device. It is difficult to advance the ViperWire if the orbital atherectomy device is on the wire. The device may have to be removed in order to re-advance the wire to the distal segment of the vessel. This increases the fluoroscopy and procedural times. Another option is to activate the GlideAssist, which decreases the friction between the device and the ViperWire and allows the operator to advance the wire distally.  

Study limitations. This was a small, single-center study with short follow-up duration. There was no comparison with patients who underwent orbital atherectomy without GlideAssist. An angiographic core laboratory did not perform quantitative coronary angiography. A clinical events committee did not adjudicate angiographic and clinical endpoints. Periprocedural cardiac biomarkers were not obtained in patients unless clinically indicated. 

Conclusion

Our initial experience with the GlideAssist function suggests that it may be a useful feature to facilitate the delivery of the orbital atherectomy crown to difficult-to-reach lesions. Further data are needed to demonstrate the feasibility and safety of this function. 

References

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7. Lee MS, Shlofmitz E, Goldberg A, Shlofmitz R. Multicenter registry of real-world patients with severely calcified coronary lesions undergoing orbital atherectomy: 1-year outcomes. J Invasive Cardiol. 2018;30:121-124. 

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12. Lee MS, Shlofmitz E, Kong J, et al. Outcomes of patients with severely calcified aorto-ostial coronary lesions who underwent orbital atherectomy. J Interv Cardiol. 2018;31:15-20.

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14. Gambhir DS, Batra R, Singh S, Kaul UA, Arora R. Burr entrapment resulting in perforation of right coronary artery: an unreported complication of rotational atherectomy. Indian Heart J. 1999;51:307-309.

15. Kimura M, Shiraishi J, Kohno Y. Successful retrieval of an entrapped Rotablator burr using 5 Fr guiding catheter. Catheter Cardiovasc Interv. 2011;78:558-564. 

From the ¹Division of Interventional Cardiology, UCLA Medical Center, Los Angeles, California; ²Division of Interventional Cardiology, Washington Hospital Center, Washington, D.C.; ³Division of Cardiology, Korea University Hospital Guro, Seoul, South Korea; and ⁴Division of Cardiology, St. Francis Hospital, Roslyn, New York. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted April 20, 2019 and accepted May 1, 2019.

Address for correspondence: Dr Michael S. Lee, UCLA Medical Center, 100 Medical Plaza, Suite 630, Los Angeles, CA 90095. Email: mslee@mednet.ucla.edu