"Single-Operator" Technique for Advancing the Orbital Atherectomy Device

Abstract: Objective. We assessed the feasibility and safety of the “single-operator” technique in which the operator autonomously advanced the orbital atherectomy (OA) device while maintaining wire position. Background. Severe coronary artery calcification (CAC) increases the complexity of percutaneous coronary intervention (PCI), and is associated with lower procedural success rates and higher rates of adverse outcomes, including death, myocardial infarction, target-vessel revascularization, and stent thrombosis. OA is an effective treatment  strategy to facilitate optimal stent expansion. Reluctance with the utilization of OA may stem from operator inexperience, unavailability of an experienced assistant, and the potential for proximal and distal wire migration during advancement of the device, leading to increased procedural and fluoroscopic time. Methods. Fifty consecutive patients who underwent OA from February 2014 to September 2016 were included in this prospective study. The primary endpoint was successful delivery of the OA device to the lesion while maintaining distal wire position and procedural success. Results. The primary endpoint was achieved in all 50 patients (100%). The 30-day major adverse cardiac and cerebrovascular event rate was 6.0%, due to death (2%) and myocardial infarction (4%). Target-vessel revascularization, stroke, and stent thrombosis did not occur. Perforation occurred in 2%. Slow-flow occurred in 4%, but resolved with intracoronary vasodilator therapy and achieved Thombolysis in Myocardial Infarction grade 3 flow. Flow-limiting dissection did not occur. Conclusion. The single-operator technique is feasible, can be used to maintain wire position while the OA device is advanced, and obviates the need for a skilled assistant when advancing the OA device. 

J INVASIVE CARDIOL 2017;29(3):92-95

Key words: orbital atherectomy, calcification, percutaneous coronary intervention, coronary artery disease

The presence of severe coronary artery calcification (CAC) increases the complexity of percutaneous coronary intervention (PCI).¹ It is associated with lower procedural success rates and higher rates of outcomes including death, myocardial infarction (MI), target-vessel revascularization (TVR), and stent thrombosis.^1,2 

Coronary atherectomy is an effective treatment strategy for patients with severe CAC.¹ For almost 30 years, rotational atherectomy (RA) has been a mainstay for the treatment of severe CAC. The ORBIT II trial reported the safety and efficacy of orbital atherectomy (OA), with high angiographic and procedural success rates and low rates of death, MI, and TVR at 30 days, 1 year, 2 years, and 3 years.^3-6 Both RA and OA traditionally require a serviceable assistant for successful completion of these complex procedures. Typically, the assistant must fix the back of the specialized guidewire in place to provide a rail system for advancement of the device over the wire to the lesion while preventing distal and proximal guidewire migration. The assistant is also required to lift up and advance the back end of the device in synchrony while the operator carefully advances the RA burr or OA crown. An inexperienced assistant may inadvertently pull the wire back, leading to loss of wire position and necessitating the readvancement of the guidewire, with subsequent increases in procedural and fluoroscopic times. 

Previously, we reported the feasibility and safety of the “single-operator” technique, in which the operator autonomously advances the RA device to the lesion without an assistant to fix the RotaWire distally or simultaneously lift the advancer to facilitate its delivery.⁷ Since the approval of OA by the Food and Drug Administration in 2013, it has been the device of choice for the treatment of severe CAC at our institution given its ease of use, favorable clinical data, and mechanistic advantages compared with RA. We conducted a prospective study to assess the feasibility and safety of the single-operator technique for the use of OA in severe CAC.

Methods

Study population. From February 2015 to September 2016, a total of 50 patients underwent OA (Cardiovascular Systems, Inc [CSI]) at the UCLA Medical Center in Los Angeles, California, with the single-operator technique. Patients with severe CAC, a reference vessel diameter ≥2.5 mm and ≤5.0 mm, and a stenosis of ≥70% or fractional flow reserve assessment ≤0.80 for intermediate coronary artery stenosis were included in this analysis. Severe CAC was defined as the presence of radioopacities on fluoroscopy involving both sides of the arterial wall or intravascular ultrasound (IVUS) revealing ≥270° of CAC. Patients with ST-elevation myocardial infarction were excluded. The institutional review board approved the review of the data. 

Device description, procedural technique, and medical treatment. The CSI OA system has been previously described.¹⁰ OA modifies calcified plaque with a differential sanding mechanism of action. Unlike RA, OA works in a bidirectional manner, as it ablates going forward as well as backward. A 6 Fr guiding catheter was used in all cases. The 0.012˝ ViperWire (CSI) was used to cross the lesion unless it was difficult to traverse, necessitating a workhorse wire followed by exchanging out for the ViperWire through an over-the-wire balloon. The ViperSlide lubricant (CSI) was infused through the drive shaft in order to reduce friction while the device was advanced over the guidewire. Thirty-micron diamonds then coat the 1.25 mm eccentrically mounted crown, which rotates and laterally expands utilizing centrifugal force, resulting in contact with the calcified plaque in an elliptical motion. 

The single-operator technique used for RA was also used for OA. The crown of the OA was advanced over the ViperWire, and the device was activated prior to entering the guiding catheter to confirm its proper function (Figure 1). Once the OA crown entered the Tuohy Borst, the shaft was looped in an “S” shape and the electric motor-powered handle was positioned close to the Tuohy Borst (Figure 2). Specifically, a Co-Pilot bleedback control valve (Abbott Vascular) was used in all cases, which we recommend because the crown can be freely advanced while the seal is closed (released position). Under fluoroscopic guidance, the crown was advanced over the ViperWire with the left hand as the right hand pulled the wire back in synchrony (Figure 3) until the crown was delivered proximal to the lesion while the slack was taken out of the shaft (Figure 4).

Watch a video demonstration of the single-operator technique here. 

After initial activation at low speed (80,000 rpm), high-speed atherectomy (120,000 rpm) was only performed if the reference vessel diameter is ≥3 mm. Each pass was limited to ≤20 seconds in duration. After OA was performed, standard PCI techniques were used. No temporary pacemaker was inserted prior to OA. Drug-eluting stent (DES) was the default stent type unless prolonged dual-antiplatelet therapy was contraindicated or there was impending surgery. 

Patients were pretreated with dual-antiplatelet therapy prior to OA. Weight-based unfractionated heparin was used to achieve an activated clotting time >250 seconds. Following PCI, dual-antiplatelet therapy was prescribed for at least 1 month for bare-metal stent and 1 year for drug-eluting stent. Optimal medical therapy included beta-blocker, angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker, and statin, unless contraindicated. 

Study endpoints and clinical follow-up. The primary endpoint was procedural success without the need to take the crown off the ViperWire to reposition it. Procedural success was defined as residual stenosis ≤30% and Thrombolysis in Myocardial Infarction (TIMI) flow grade 3 without death, emergency coronary artery bypass graft surgery, and/or PCI during the first 24 hours. Major adverse cardiac and cerebral events were defined as the composite of death, MI, TVR, and stroke. Myocardial infarction was defined as recurrent symptoms with new ST-segment elevation or re-elevation of cardiac markers to at least twice the upper limit of normal. TVR was defined as a repeat revascularization of the target vessel because of restenosis or thrombosis. The Academic Research Consortium definition of stent thrombosis was used.⁸ A dedicated PCI database recorded demographic, angiographic, and procedural data, and clinical outcomes were collected from medical records.

Statistical analysis. Continuous variables are expressed as mean ± standard deviation. Categorical variables are expressed as percentages. All data were analyzed using SPSS version 20.0 (SPSS-PC, Inc). 

Results

Baseline characteristics. The mean age was 62 ± 11 years, and the majority of patients were male (Table 1). All patients underwent OA with heparin, and the majority of patients were loaded with a P₂Y₁₂ inhibitor (Table 2). Both low-speed and high-speed were used in 72% of patients. The mean number of runs per case was 3.3 ± 1.3. The mean number of stents used was 1.5 ± 0.4. 

Clinical outcomes at 30 days. The primary endpoint was achieved in all 50 patients (Table 3). Major adverse cardiac and cerebral events occurred in 6.0% due to death (2%) and MI (4%). TVR, stroke, and stent thrombosis did not occur. Perforation occurred in 1 patient (2%). A 43-year-old male had cardiogenic shock after cardiac arrest at home, subsequent cardiopulmonary resuscitation and intubation, and insertion of enhanced extracorporeal membrane oxygenation for severe left ventricular dysfunction with an ejection fraction of 10% while on four vasopressors. He underwent emergent OA of the left main and left anterior descending arteries because he was not a candidate for surgical revascularization. Coronary perforation occurred after stenting the mid-left anterior descending artery and was successfully treated with implantation of a polytetrafluoroethylene-covered stent. Slow-flow occurred in 4%, but resolved with intracoronary vasodilator therapy and achieved TIMI grade 3 flow. There was no flow-limiting dissection.

Discussion

The single-operator technique is feasible and safe with OA. All patients underwent successful OA without the loss of wire position while advancing the crown over the ViperWire. 

Despite the presence of CAC in approximately 38% of people during angiography and 73% with IVUS,⁹ coronary atherectomy is used in 3% to 5% in select high-volume centers and <1% in others.¹⁰ Reasons for underutilization of coronary atherectomy include operator inexperience, the lack of robust long-term clinical data, increased cost and time of the procedure, and unavailability of a reliable assistant to maintain wire position during advancement. The single-operator technique obviates the need for an assistant to help deliver the OA device to the calcified lesion and should be one less reason limiting the underutilization of coronary atherectomy in the treatment of severe CAC. 

Securing the distal wire position after the ViperWire traverses the calcified lesion is vital to minimizing procedural and fluoroscopic time. Without a skilled assistant, the wire can migrate proximal to the lesion while advancing the crown, which may necessitate the removal of the crown from the ViperWire due to difficulty in readvancing the wire while it is inside the OA device. Distal wire migration can occur if the ViperWire is not properly fixed in place, possibly leading to disengagement of the guiding catheter from the coronary artery ostium due to excessive slack in the rail system. Furthermore, migration of the wire distally can cause wire perforation as the ViperWire is a stiffer wire than a workhorse wire. The single-operator technique gives the operator full control of both the ViperWire and OA device, thereby removing the variable of an inexperienced assistant and permitting autonomous delivery of the OA device to the lesion.

Learning this technique can be accomplished by initially performing it in uncomplicated cases with focal lesions in straight segments of the vessel in which loss of wire position can be easily be corrected by readvancing the wire. Mastery of this technique can be achieved within the first 3 cases. With RA, the burr needs to be removed from the guiding catheter, exchanged for a larger burr, and readvanced to the lesion if upsizing to a different burr is needed for a large vessel. However, OA can ablate to a greater degree by switching from low speed to high speed by the push of a button without removing the crown for another. 

The single-operator technique is particularly useful if an experienced cath lab technologist or fellow is unavailable to assist during OA. While one may stop after the diagnostic coronary angiogram and reschedule the case when an experienced assistant is available, this may not be a logistically feasible option given the busy schedule of operators and limited cath lab availability. 

Study limitations. This was a non-randomized analysis of outcomes at one center by a single operator (MSL). The number of patients in this study was small, and the duration of follow-up was short (30 days). MI may have been underdiagnosed because cardiac biomarkers were not routinely measured after OA. 

Conclusion

The single-operator technique is feasible and safe when performing OA for the treatment of severe CAC. Performing this technique is not difficult, may be an attractive option when a competent assistant is not available to help during OA, and should no longer be a reason why OA is not used for the treatment of severe CAC. The results of our study require validation by other operators who perform this technique.

References

1.     Lee MS, Shah N. The impact and pathophysiologic consequences of coronary artery calcium deposition in percutaneous coronary interventions. J Invasive Cardiol. 2016;28:160-167.

2.     Lee MS, Yang T, Lasala J, Cox D. Impact of coronary artery calcification in percutaneous coronary intervention with paclitaxel-eluting stents: two-year clinical outcomes of paclitaxel-eluting stents in patients from the ARRIVE program. Catheter Cardiovasc Interv. 2016;88:891-897.

3.     Chambers JW, Feldman RL, Himmelstein SI, et al. Pivotal trial to evaluate the safety and efficacy of the orbital atherectomy system in treating de novo, severely calcified coronary lesions (ORBIT II). JACC Cardiovasc Interv. 2014;7:510-518.

4.     Généreux P, Lee AC, Kim CY, et al. Orbital atherectomy for treating de novo severely calcified coronary narrowing (1-year results from the Pivotal ORBIT II trial). Am J Cardiol. 2015;115:1685-1690.

5.     Généreux P, Bettinger N, Redfors B, et al. Two-year outcomes after treatment of severely calcified coronary lesions with the orbital atherectomy system and the impact of stent types: insights from the ORBIT II trial. Catheter Cardiovasc Interv. 2016;88:369-377. 

6.     Chambers JW. ORBIT II final 3-year data. Presented on May 5, 2016. SCAI 2016 Scientific Sessions, Orlando, Florida.

7.     Lee MS, Wiesner P, Rha SW. Novel technique of advancing the rotational atherectomy device: “single-operator” technique. J Invasive Cardiol. 2016;28:183-186.

8.     Cutlip DE, Windecker S, Mehran R, et al; Academic Research Consortium. Clinical end points in coronary stent trials: a case for standardized definitions. Circulation. 2007;115:2344-2351.

9.     Mintz GS, Popma JJ, Pichard AD, et al. Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions. Circulation. 1995;91:1959-1965.

10.     Mota P, Santos R, Pereira H, et al. Facts on rotational atherectomy for coronary artery disease: multicentric registry (Abstr). Paper presented at EuroPCR; May 21, 2013; Paris, France.

From the ¹UCLA Medical Center, Los Angeles, California; and ²St. Francis Hospital — The Heart Center, Roslyn, New York.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Lee and Shlofmitz report honoraria from CSI. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript submitted October 6, 2016, provisional acceptance given October 13, 2016, final version accepted October 25, 2016.

Address for correspondence: Michael S. Lee, MD, Associate Professor of Medicine, 100 Medical Plaza Suite 630, Los Angeles, CA 90095. Email: mslee@mednet.ucla.edu