Procedural Outcomes of Orbital Atherectomy Treatment of Peripheral Arterial Disease in an Outpatient Office-Based vs Hospital Setting

ABSTRACT: Background: Despite the increasing use of atherectomy, few studies have compared outcomes of endovascular procedures performed in an outpatient office-based laboratory (OBL) to those performed in the traditional hospital setting. As the trend for increased outpatient treatment continues, it is critical to begin to assess the procedural outcomes of atherectomy in the OBL setting. Methods: We analyzed the CONFIRM registry series, a data collection of patients with peripheral arterial disease (PAD) who were treated with orbital atherectomy in both the OBL and hospital settings. Results: We found that 36% of patients in both the hospital and OBL groups were classified as Rutherford class III (P=.96) and the lesions treated were moderately to severely calcified (angiographic evaluation) in 83% and 90% of patients in the hospital and OBL setting, respectively (P=.07). Final residual stenosis after adjunctive therapy was 10%±11% in the hospital group and 11%±17% in the OBL group (P=.32). Dissections, including flow limiting and non-flow limiting, occurred in 11.4% of lesions in the hospital group vs 6.5% in the OBL group (P=.12). Adjusted logistic regressions showed no difference in any individual complication rate or the overall complication rate. Conclusions: Orbital atherectomy treatment of PAD in an OBL was found to be comparable to treatment in a hospital setting. Due to the emergence of more OBLs utilizing orbital atherectomy, a follow-up prospective study is warranted to further investigate the comparative outcomes within a larger patient population. 

VASCULAR DISEASE MANAGEMENT 2014;11(2):E37-E43

Key words: atherectomy, peripheral artery disease, calcified lesions, endovascular therapy, office-based laboratories

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Peripheral endovascular intervention for symptomatic peripheral arterial disease (PAD) is the fastest growing treatment area in endovascular medicine. However, heavily calcified and occluded arterial segments are predictors of poor long-term patency.¹ Percutaneous transluminal angioplasty (PTA) often produces insufficient results in more calcified lesions, leading to a high rate of bail-out stenting.² Self-expanding nitinol stents have improved outcomes in PAD, however reported fracture rates have ranged from 3% to 37%, with higher fracture rates in longer and more calcified lesions.^2-4 Atherectomy has emerged as a treatment option for heavily calcified peripheral lesions to improve luminal diameter with the potential to prepare the lesion for more uniform circumferential expansion with PTA and better stent apposition.^5-8  

With the advent of endovascular office-based laboratories (OBL), many minimally invasive vascular procedures are now performed outside the traditional hospital setting. Currently, limited data exist to evaluate the various technologies used within the OBL setting, and what data do exist have not been compared to data generated within a traditional hospital setting in a similar patient population. The CONFIRM series, a prospective registry of PAD patients with lesions treated with orbital atherectomy includes procedural information from both OBLs as well as hospital settings. 

This paper compares the procedural success of the Diamondback 360 Orbital Atherectomy System (OAS) developed by Cardiovascular Systems, Inc. (CSI) to treat PAD in an outpatient OBL setting compared to the traditional hospital setting when matched for similar patient demographics. 

METHODS 

The OAS is a novel system for the treatment of PAD and has been previously described.^9-11 This percutaneous endovascular system features a diamond abrasive crown that spins eccentrically to remove calcific plaque and thus improve blood flow through the target lesion. 

The CONFIRM registry series, sponsored by CSI, prospectively enrolled patients receiving medically necessary treatment in accordance with the device’s Instructions for Use.¹² Subjects gave informed consent and the study conformed to institutional guidelines. Descriptive data regarding the ability of the OAS to modify resistant plaque in the entire leg were collected. Procedural data were collected for 3,135 PAD patients in whom the OAS was used to treat at least one lesion. To be eligible, sites were required to perform more than 50 peripheral endovascular procedures per year, have the OAS available for use in their OBL or hospital, and be trained on the use of the system. Plaque morphology was assessed by the treating physician based upon angiographic images. Final residual stenosis was reported by the treating physician after all adjunctive therapies were completed. 

Statistical analyses included Student t test for continuous measures, Chi-squared test for categorical measures, and logistic regression for complication rates, adjusting for differing demographics and procedural data. Baseline factors that were statistically significantly different between groups were entered into a multivariate model, and the P value for the group with these terms in the model was reported. P values were calculated for each characteristic and a P value of less than .05 was considered statistically significant. Patients with a missing data point were excluded from analysis; therefore the number of patients listed within the tables throughout the manuscript may vary slightly. Statistical analyses were performed using SAS v. 9.3.

RESULTS

Study Population

Between October 2009 and June 2011, procedural data were recorded for 3,135 patients (4,766 lesions) treated with the OAS at 212 sites in the United States. In the traditional hospital setting, there were 3,060 patients (4,658 lesions) treated in over 200 hospitals compared to 75 patients (108 lesions) treated in 4 OBLs. Demographic data for patients treated in the hospital setting vs the OBL setting are presented in Table 1. 

There were no appreciable differences between the two groups in regard to gender, smoking habits, history of diabetes, hypertension, hyperlipidemia, coronary artery disease, or renal disease. Mean Ankle Brachial Index (ABI) was similar: 0.61±0.27 and 0.59±0.27 for hospital and OBL settings, respectively (P=.69). In both settings, 36% of patients were classified as Rutherford class III (P=.96). However the hospital group had a higher incidence of patients with critical limb ischemia (Rutherford class IV-VI): 44% vs 23% (P=.0003). This is expected since many critical limb ischemia patients are already hospitalized when the vascular specialist is consulted, whereas the treating physician may feel that some elective cases are best treated in an outpatient setting.

Procedural Data. Based on the investigator’s visual estimate, 83% and 90% of lesions were moderately to severely calcified in the hospital and OBL settings, respectively (P=.07). Procedural data are presented by group in Table 2.  As shown, in both settings the physician treated a similar number of lesions. The number of lesions treated both above the knee and below the knee was similar in both settings. However, in the hospital group lesions were longer, the mean number of devices used per patient was greater, and the mean total OAS run time was longer per lesion.

Pre-procedure stenosis was 88%±12% in the hospital group and 83%±13% in the OBL group (P<.001). Post-OAS stenosis was 35%±19% in the hospital group compared to 42%±19% in the OBL group (P=.003). Final residual stenosis, after adjunctive therapy, was 10%±11% in the hospital group and 11%±17% in the OBL group (P=.32). 

Post atherectomy, 69.0% and 76.9% of lesions in the hospital and OBL settings, respectively, were treated with PTA, making it the most common adjunctive therapy (P=.08). Stents used alone or with PTA were utilized as an adjunctive therapy more frequently in the OBL group (14.8% vs 5.6%, P<.001). Additional adjunctive therapy data are presented in Table 3.  

Procedural Complications

As shown in Table 4, the most common procedural complication was dissection, including flow-limiting and non-flow-limiting, which occurred in 11.4% of lesions in the hospital group vs 6.5% of lesions in the OBL group (P=.12). Of the 7 dissections reported in the OBL group, 6 were treated with a stent and none were classified as flow limiting by the treating physician. In the hospital group, dissections were attributed to PTA in 45.3% of lesions.

None of the complication rates were significantly different by group using an unadjusted logistic regression; however, the overall event rate was significantly greater in the hospital group (22.1% vs 13.0%, P=.03). Adjusted logistic regressions were also conducted, adjusting for significantly different demographic and procedural data (Rutherford class, lesion length, adjunctive therapy, number of devices, total running time, and lesion location). After adjusting for these factors, there was no difference in any individual complication rate or the overall complication rate.

DISCUSSION

To date, published data evaluating acute outcomes of endovascular technologies for treatment of PAD in the OBL setting compared to the traditional hospital setting are almost nonexistent. However, several published abstracts on peripheral interventions, including atherectomy, indicate that these types of interventions can be performed in the office-based setting with low complication rates.^13-15 

The OAS provides an effective means to reduce atherosclerotic plaque in peripheral arterial lesions. Demographics of the patients treated in the OBL setting and hospital setting were similar in regards to gender and cardiovascular risk characteristics. Although the difference in preprocedural stenosis was statistically significant, the difference was considered not clinically relevant in terms of affecting procedural outcome of the OAS or the final percentage of residual stenosis. The increased mean total OAS run time in the hospital group may be expected since the lesions treated in the hospital setting were longer compared to lesions treated in the OBL setting. The more frequent use of adjunctive stents in the OBL group is in contradiction to the lower incidence of reported dissections in this same setting and may be related to the operators’ reluctance to discharge a patient with a residual minor dissection immediately following the procedure. Final residual stenosis attained post OAS with adjunctive therapy in both settings was similar, demonstrating that comparable results can be achieved in an OBL setting and hospital setting. 

The rate of procedural complications in the OBL group was low, and lower than those seen in the hospital group. The overall incidence of complications was 13.0% in the OBL group vs 22.1% in the hospital group; however the difference is not statistically significant after adjusting for differing demographics, and therefore may represent a differing level of case complexity between the two groups. 

CONCLUSION 

The use of OAS in an OBL resulted in similar procedural outcomes of those seen in the hospital setting. The final residual stenosis rate was equivalent in both groups. These data show a statistically significant lower overall procedural complication rate in the OBL compared to results reported from traditional hospital endovascular suites; however after adjusting for different demographic and procedural data the difference in event rates was not statistically significant. Due to the emergence of more OBLs and the increased use of orbital atherectomy in this setting over the last 2 years, a follow-up prospective study is warranted to re-evaluate comparative outcomes with a more similar subset of patients in each group.

Editor’s Note: Disclosure:  The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Mayeda reports consultancy; honoraria; payments and reimbursements for educational programs, speakers bureau, and travel; and stock options with CSI. Dr. Julien reports consultancy, honoraria, and reimbursements from CSI. Dr. Lesar reports consultancy to CSI, Medtronic, Boston Scientific, and Bayer HealthCare, as well as work with Vascular Growth Services. Drs. Pliagas, Lew, and Bajaj report no disclosures related to the content of this manuscript. 

Manuscript received May 4, 2013, provisional acceptance May 21, 2013, accepted September 13, 2013. 

Address for correspondence: Guy Mayeda, MD, Los Angeles Cardiology Associates, 1245 Wilshire Boulevard, Los Angeles, CA 90017, United States. Email: gmayeda@lacard.com 

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