Robotic Peripheral Vascular Intervention With Drug-Coated Balloons is Feasible and Reduces Operator Radiation Exposure: Results of the Robotic-Assisted Peripheral Intervention for Peripheral Artery Disease (RAPID) Study II

Abstract: Background. A robotic-assisted platform (CorPath System; Corindus Vascular Robotics) is feasible for peripheral vascular intervention (PVI) for the treatment of femoropopliteal lesions. Objectives. This study was designed to determine the feasibility and safety of robotic PVI for treating femoropopliteal lesions with drug-coated balloon (DCB), and to evaluate the effect of robotic PVI on operator radiation exposure during robotic PVI. Methods. This prospective, single-arm trial enrolled patients with symptomatic peripheral arterial disease affecting the femoropopliteal artery. The primary outcome measure was clinical success, defined as <50% residual stenosis and the absence of periprocedural device-related serious adverse events. Operator radiation exposure was compared between the robotic cockpit vs the tableside. Results. This study enrolled 20 patients (age, 65.5 ± 9.9 years; 60% men), with the majority (75%) Rutherford category 3-4. A total of 24 lesions (lesion length, 49.8 ± 37.5 mm) were treated with DCB and 91.7% were located in the superficial femoral artery. Clinical success was 100% and provisional stenting was required in 1 lesion. Fluoroscopy time was 7.3 ± 3.3 minutes and operator radiation exposure was 1.9 ± 2.9 μSv, which was reduced by 96.9 ± 5.0% when compared with the table-side (control) dosimeter (P<.001). There were no adverse events associated with the use of the robotic system. Conclusions. These data demonstrate the safety and feasibility of using a robotic-assisted platform for treating femoropopliteal lesions with rapid-exchange interventional devices, and show 96.9% reduction in radiation exposure for the primary operator. 

J INVASIVE CARDIOL 2020;32(10):380-384. 

Key words: PVI, peripheral artery disease, robotic-assisted

In recent years, robotic platforms have emerged as an alternative to the traditional manual manipulation of intravascular devices during percutaneous coronary (PCI) and peripheral vascular intervention (PVI).^1-3 Advantages of using robotics for PCI include reduction of geographic miss and the reduction of operator radiation exposure.^1,4 We previously demonstrated the utility of using a robotic platform (CorPath 200 System; Corindus Vascular Robotics) for PVI.³ This previous clinical trial, the RAPID (Robotic-Assisted Peripheral Intervention for peripheral arterial Disease) study, was conducted for Food and Drug Administration (FDA) marketing clearance. As such, the trial was limited to using only FDA-approved rapid-exchange devices for femoropopliteal interventions, which at the time consisted of percutaneous transluminal angioplasty (PTA) balloons only. Due to this limitation, no drug-coated balloons (DCBs) were used and if stenting was required, stent delivery had to be performed manually. The RAPID II study was designed to assess the feasibility of the CorPath System to treat femoropopliteal lesions with commercially available rapid-exchange DCB, and to determine the effect of robotic PVI on operator radiation exposure. 

Methods

Design and study population. The RAPID II study was a prospective, single-arm, single-center, non-randomized feasibility study of robotic-assisted PVI (ClinicalTrials.gov identifier, NCT02742077). The objectives of the study were to evaluate the feasibility and safety of the CorPath System in performing endovascular intervention of the femoropopliteal artery using DCB. Additionally, the effect of robotic PVI on operator radiation exposure was evaluated. Patients were eligible for enrollment if they had symptomatic peripheral arterial disease as evidenced by either the presence of critical limb ischemia (including tissue loss or rest pain) or lifestyle-limiting claudication that required intervention. Lesion criteria for enrollment included femoropopliteal lesions that exhibited >50% stenosis or occlusion of up to 120 mm in length as determined by preindex procedure imaging (either angiography or magnetic resonance angiography). Patients were excluded if they had any of the following target-vessel characteristics: previously treated with bypass; evidence of previous perforation or dissection; adjacent acute thrombus; or a pre-existing target-artery aneurysm, perforation, or dissection prior to initiation of the index procedure. The study was conducted in compliance with the Declaration of Helsinki and was approved by the local ethics committee. All patients provided written informed consent prior to study participation.

Robotic System. The CorPath 200 System has been reviewed elsewhere.¹ Briefly, the system consists of two primary components, a remote workspace and a tableside robotic unit (Figure 1). The remote workspace is a radiation-shielded mobile workstation where a seated physician performs the PVI by use of two joysticks to independently manipulate guidewires and catheters. The remote workspace is also designed to integrate other manufacturer’s angiographic and hemodynamic video monitors, contrast injectors and balloon inflation controls in order to afford the operator improved visualization and control of these aspects of the endovascular procedure. As the physician manipulates the joysticks, the signals are remotely delivered through a communication cable to the tableside robotic unit, which consists of an articulating arm, robotic drive, and single-use cassette. The articulating arm supports the robotic drive, which houses the cassette. The cassette translates the signals from the joystick manipulations into precise movements of guidewires and rapid-exchange catheters. 

Interventional procedure. All procedures in the study were performed by standard techniques. Common femoral artery access was obtained in all subjects followed by attachment of the cassette to the sheath using a Tuohy-Borst system (Copilot Bleedback Control Valve; Abbott Vascular). Balloon angioplasty of the femoropopliteal vessels was then performed followed by Elutax SV Rx DCB (Aachen Resonance GmbH), with the option for provisional stenting for flow-limiting dissections. Provisional stenting was not considered a failure of the robotic system.

Outcome measures. The primary outcome measure was clinical success, which was defined as <50% residual stenosis in robotic-PVI (R-PVI) treated lesions at the completion of the procedure and the absence of device-related serious adverse events within 72 hours of the procedure or prior to hospital discharge, whichever occurred first. Procedural outcome measures included fluoroscopy time, patient radiation exposure, contrast volume, procedure time (overall and CorPath), and adverse events. Patient-specific outcome measures included pre- and postprocedure assessments of ankle-brachial index (ABI), toe-brachial index (TBI), peak systolic velocity ratio (PSVR) measured by duplex ultrasound, and percent diameter stenosis. In addition, operator radiation exposure was recorded on personal Enterprise Dose Dashboard (EDD; Landauer) dosimeters and total radiation during each case was measured on a tableside (control) EDD dosimeter. 

Statistical analysis. As this was a feasibility study, formal a priori hypothesis testing was not performed. It was determined that a sample size of up to 20 patients would provide a reasonable degree of precision for events that occurred during the study. Specifically, at an assumed success rate of 99%, the expected confidence interval (CI) width for the success rate based on a two-sided 95% exact binomial CI was determined to be <19%. Descriptive statistics for categorical variables (frequency and percentage) and continuous variables (number of observations, mean, and standard deviation) were used to present results of the patient, lesion, and procedural characteristics. The PSVR and percent diameter stenosis were compared before and after R-PVI using a repeated measures analysis of variance. The percent reduction in operator radiation exposure, as well as the revascularization results, ABIs, and TBIs, were compared with pre-revascularization indices, and were evaluated using the Wilcoxon signed-rank test (a non-parametric paired t-test).

Results

Subject demographic and baseline characteristics are summarized in Table 1. Twenty subjects, mean age 65.6 ± 9.9 years (60% men) were enrolled and underwent R-PVI. The preprocedure Rutherford classifications were stage 2 (25%), 3 (60%), and 4 (15%). Most patients (85%) had intermittent claudication while 15% had critical limb ischemia. The most common comorbidities were dyslipidemia (90%) and hypertension (85%).

Twenty-four lesions were treated, with the majority (91.7%) in the superficial femoral artery and the remainder  (8.3%) in the popliteal artery. Lesion characteristics included a mean lesion length of 49.8 ± 37.5 mm, with the majority deemed to have mild vessel tortuosity (93.1%) and calcification (66.7%) (Table 2). 

Table 3 summarizes pre- and postprocedure assessments and Table 4 summarizes procedure data. Accordingly, there was a significant relief of high-grade stenosis (86.3 ± 10.5% to 8.8 ± 10.8%; P<.001). Blood flow duplex ultrasound exhibited a significant improvement, as the PSVR improved from 4.3 ± 3.4 at baseline to 1.0 ± 0.3 post procedure (P<.001). Likewise, there was also a significant improvement in ABI, from 0.7 ± 0.2 before the procedure to 1.0 ± 0.2 post procedure (P<.001). Only 1 lesion (4.2%) required provisional stenting, which was performed manually. The primary outcome measure of clinical success was achieved in 100% of treated lesions. Similar results were observed when the recently published Peripheral Academic Research Consortium definition of acute technical success for peripheral revascularization was used. These success criteria require a residual stenosis of <30% after stenting and <50% after balloon angioplasty or atherectomy in the absence of a flow-limiting dissection or residual pressure gradient.⁵ Using this definition, all 24 treated lesions were successfully treated, including 23 treated with angioplasty with residual stenosis of <50% (mean, 9.1% ± 10.8%; range, 0%-30%), and the 1 lesion that required provisional stenting had a final residual stenosis of 0%. Total procedure times (from sheath insertion to sheath removal) and fluoroscopy times were 47.5 ± 14.4 minutes and 7.3 ± 3.3 minutes, respectively. Patient radiation dose-area product was 566.7 ± 391.5 mGy•m². 

Operator radiation exposure is reported in Table 5. We evaluated both the physician operator, who operated the CorPath System from the shielded cockpit, and the tableside operator, who obtained vascular access and coordinated the placement of devices into the robotic cassette. Compared with the mean tableside (control) EDD dosimeter reading, 95.8 ± 147.0 µSv, the mean operating physician dose and tableside operator doses were 1.9 ± 2.9 µSv and 4.1 ± 8.0 µSv, respectively. This corresponded to reductions in radiation exposure of 96.9 ± 5.0% and 95.4 ± 7.8%, respectively (P<.001 for both) (Figure 2). 

Only 3 minor adverse events (all access-site hematomas) were reported. No adverse events related to the robotic system were reported.

Discussion

This study demonstrates that R-PVI is safe and feasible for the treatment of femoropopliteal lesions with contemporary interventional therapy with DCB. The entire procedure was completed robotically in 95% of cases and the primary outcome measure, clinical success, was achieved in all treated lesions. Furthermore, no adverse clinical events related to the CorPath robotic platform were observed. 

As opposed to our previous study, we evaluated operator radiation exposure in the RAPID-II study. Working within the radiation-shielded cockpit, the mean operator radiation dose was significantly reduced by 96.9 ± 5.0% when compared with the tableside monitor (P<.001). This is consistent with previously reported results for R-PCI in which a median 92.5% reduction was reported in one study,¹ and a median 99.3% reduction in head-level exposure was reported in another study.⁴ We also showed that the tableside operator, who obtained vascular access and facilitated the exchange of devices into the robotic cassette, but was otherwise removed from the table during the procedure, also exhibited a significant reduction in radiation exposure (95.4%). Occupational radiation exposure by interventionists has been linked to increased risk of the development of cataracts, and potentially malignancies and genetic abnormalities.⁶ Furthermore, interventionists have an increased incidence of orthopedic injuries when compared with other physician specialties due to the extensive burden of wearing heavy lead aprons at the table side to protect from radiation exposure.^7-10 The concern of radiation exposure is higher for peripheral vascular procedures, where effective radiation dose exposure is 4-fold greater than PCI procedures, making the potential operator benefit even greater.¹¹ 

Patient radiation exposure is an additional concern. In the previous study, we showed that the fluoroscopy time was generally shorter (6.8 ± 3.4 minutes) than the mean reported for similar patients (13-15 minutes) who underwent manual procedures.^3,12,13 In the current study, procedures were conducted on longer lesions (49.8 ± 37.5 mm). Despite this, the total fluoroscopy time was only marginally greater (7.3 ± 3.3 minutes) than in the RAPID study. Furthermore, the number of patients requiring provisional stenting was substantially lower when compared with the RAPID study (5.0% vs 34.5%), likely reflecting the evolution in therapy for the treatment of femoropopliteal lesions, with DCB becoming the primary modality of treatment. 

Study limitations. This study was conducted at a single center with experienced peripheral operators; therefore, it is not known if the results are generally applicable across a wider range of users. Furthermore, the study was limited to patients with relatively shorter lesions. Evaluation of the robotic system for treating longer, more complex lesions at multiple centers is needed. 

Conclusion

This study demonstrates the feasibility and safety of using a robotic-assisted vascular system for femoropopliteal PVIs using contemporary treatment strategies including DCBs. Clinical success was observed in all 20 subjects without any device-related periprocedural adverse events. Furthermore, there was an associated operator radiation exposure reduction of 96.7%. 

From the ¹Division of Cardiovascular Medicine, Sulpizio Cardiovascular Center, University of California, San Diego, La Jolla, California; ²Division of Interventional Radiology, Medical University, Graz, Austria; ³Division of Angiology, Medical University, Graz, Austria; and ⁴Corindus Vascular Robotics, Waltham, Massachusetts.

Funding: This study was sponsored by Corindus Vascular Robotics.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Mahmud and Brodman report research support from Corindus Vascular Robotics. The remaining authors report no conflicts of interest regarding the content herein.

Final version accepted May 12, 2020.

Address for correspondence: Ehtisham Mahmud, MD, FSCAI, Professor and Chief, Cardiovascular Medicine, University of California Sulpizio Cardiovascular Center, La Jolla, CA 92037. Email: emahmud@ucsd.edu

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