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Latest developments in intravascular robotics

Mimi M Li BSc
19 May, 2016  

With increasing complexity in endovascular surgical techniques, catheter-based robotic systems offer a solution with improved precision and reliability, as well as radiation reduction

Mimi M Li BSc
Celia V Riga BSc MBBS MD FRCS
Imperial Vascular Unit, Division of Surgery and Cancer, Imperial College London, United Kingdom
Email: c.riga@imperial.ac.uk
 
There has been a paradigm shift in the treatment of arterial disease towards the endovascular approach in recent years, with clear advantages in terms of morbidity and mortality, particularly for patients whose co-morbidities make them otherwise unsuitable for open surgical approaches. Advancements in endovascular techniques have enabled the treatment of increasingly complex patient anatomy and pathology. 
 
Accompanied by increased procedural length and fluoroscopic screening, this often translates to a greater radiation exposure for both operator and patient. Risks of complication due to prolonged instrumentation may also be significant, even when undertaken by highly experienced endovascular specialists.
 
Medical robotic systems are an evolving technology that has seen novel applications in vascular surgery in the last few years, aiming to address the various challenges associated with complex endovascular intervention. Currently limited to a few specialist centres, endovascular catheter-based systems have been developed to treat disease in the arterial tree.
 
Endovascular robotic systems
Robotic endovascular systems enable greater precision of movement in catheter and guide wire manipulation for target vessel access, as well as stability for the delivery and placement of therapeutic devices. Their remotely-steerable nature allows operators to perform intravascular navigation seated away from the radiation source, reducing overall radiation exposure as well as the orthopaedic stress of prolonged lead garment wear (Figure 1).
 
Fig. 1: Endovascular robotics systems enable intravascular navigation seated away from the radiation source.
 
Two endovascular robotic platforms are currently available: the Hansen Sensei® and Magellan® robotic catheter systems (Hansen Medical Inc., Mountainview, CA, USA). Both platforms work similarly, allowing remote electromechanical manipulation of the robotic catheter using an instinctive motion controller, a three-dimensional hand-operated joystick. Vascular access is gained using a percutaneous or surgical technique via the transfemoral or axillary/brachial route. 
 
Target vessel access is achieved through manipulation of a hydrophilic wire and a steerable robotic catheter and outer sheath. The robotic catheter can then be retracted, with the sheath still in place to provide a stable platform for the introduction of therapeutic devices such as balloons or stents through the lumen.1
 
The original Sensei® platform was developed for electrophysiological cardiac mapping and ablation procedures via the transvenous route, receiving both CE marking and FDA clearance in 2007. Its use in endovascular surgery has been somewhat limited by the large 14Fr catheter sheath size, rendering it unsuitable in certain arterial branches, particularly in the presence of significant atherosclerosis and calcification.
 
Modifications to the next generation Magellan® platform (Figure 2), which received CE marking in 2011 and FDA clearance in 2012, have enhanced its suitability and effectiveness within the arterial tree. The smaller 6Fr leader catheter and 9Fr outer sheath allow improved access to arterial branch vessels. 
 
Fig. 2: The Magellan Robotic System: remote console and robotic arm.
 
There is enhanced manoeuvrability of the catheter tip compared to the original system, with multi-directional articulation of 180° in the leader catheter and 90° in the outer sheath, as well as independent torque control at the tip without the need for catheter shaft rotation. In addition, the robotic wire manipulator allows remote insertion, rotation, and retraction of conventional hydrophilic wires.2
 
More recently developed (CE marked April 2015, FDA clearance July 2015) is the slightly larger catheter system with a 10Fr outer sheath, 7Fr inner diameter, and 6Fr inner catheter. Treatment of a wider range of vessel branch diameters is possible with this development, as the 7Fr inner lumen allows introduction of larger stents and other therapeutic devices.3
 
Applications in endovascular therapy
Previous animal studies have provided histological evidence that intravascular robotic manipulation leads to reduced vessel wall trauma compared with conventional manual techniques.4 Preclinical studies also found robotic cannulation of vessels in the visceral segment and the aortic arch to be effective, with improved procedural and fluoroscopy times, greater economy of motion, and reduced frequency and force of vessel wall contact.5–7
 
The first clinical report of endovascular robotics use in abdominal aortic aneurysm (AAA) repair was a proof-of-concept study undertaken with the Sensei® system in 2009. The robotic platform was used for contralateral gate cannulation in the endovascular aneurysm repair (EVAR) of a 5.9cm infrarenal aneurysm in a 78-year-old patient. The procedure was successful, with computed tomography imaging at discharge and three month follow-up confirming good stent-graft positioning and no evidence of endoleak.8
 
Following this initial clinical report of its use in AAA repair, the therapeutic applications of the Sensei® platform in other endovascular procedures have also been reported. In a case of anastomotic pulmonary artery stenosis following single lung transplantation, the robotic navigation system was able to overcome the technical difficulties of manoeuvring whilst maintaining stability to allow stenting where conventional techniques had failed.9 Another report described use of the platform to treat kinked renal bridging stents eight months after branched endovascular repair of a type III thoraco-abdominal aortic aneurysm. 
 
Conventional techniques did not provide sufficient stability to support passage of the guide wire through the kinked stent against resistance. However, use of the robotic catheter system overcame this technical difficulty, allowing successful crossing and realignment of the kink with an additional stent to restore renal perfusion.10 Successful navigation of the iliofemoral arteries was also reported in a case series of 15 patients.11
 
In 2013, the first case of robotically assisted fenestrated endovascular aneurysm repair (FEVAR) was reported. This 7.3cm juxtarenal AAA in a 67-year-old patient was treated using a custom made fenestrated stent graft, with the Magellan® system being successfully deployed for renal artery cannulation. Computed tomography angiography at discharge and four-month follow-up confirmed vessel patency with no evidence of endoleak.2
 
A subsequent study of 15 patients undergoing fenestrated and branched procedures for AAA repair demonstrated the safety and feasibility of robotic navigation for target vessel cannulation in the visceral aortic segment.12 The Magellan® system has also seen promising results in uterine artery embolisation; a feasibility study with five patients reported a 100% technical success rate and significant improvements in patient symptoms.13
 
The clinical applications and advantages of the Magellan® platform are currently being investigated at 15 international vascular centres. At St Mary’s Hospital (London, UK), over 100 patients have undergone robotic-assisted endovascular intervention using the Magellan® system to date. Cases performed include: EVAR, FEVAR, thoracic stenting, iliofemoral angioplasty, carotid artery stenting, embolisations, and complex endoleak treatments. The learning curve plateau for the Magellan® system is estimated at 30 cases, with robotic set-up time also decreasing with operator experience. Average robotic set-up time is seven minutes (IQR 6–9). Average cannulation time is six minutes (IQR 3–18), with variation according to case complexity.14
 
Applications in radiation exposure reduction
The establishment of endovascular intervention in the treatment of arterial disease has led to a shift in the vascular surgical caseload towards procedures requiring ionising radiation. Whilst advancements in the field have allowed the treatment of more complex and challenging patient anatomy, this has also meant increased requirements for fluoroscopic imaging. Over the course of many years, this occupational radiation exposure could have significant harmful effects such as radio-induced cataracts, malignancy, and malformations in offspring. Reducing radiation exposure is therefore paramount to minimise these risks.
 
Occupational radiation exposure for FEVAR has been found to be significant and much higher than reported figures for conventional EVAR. Navigation of target vessels in the visceral aortic segment, particularly when requiring brachial or axillary access, has been identified as a factor in increasing radiation exposure.15
 
Endovascular robotic systems present substantial opportunity for radiation reduction. Navigation from a remote console away from the radiation source protects from radiation exposure during robotic-assisted procedural steps, thereby potentially reducing the total occupational exposure per case. Modification and development of robotic catheter technology have widened its scope of application, facilitating procedural stages such as stenting as well as cannulation of target vessels. For more technically challenging components, robotic technology use has the potential to decrease procedural and fluoroscopy time compared with conventional methods, offering the additional benefit of reduced patient radiation exposure.
 
Conclusions
Current pre-clinical and early clinical experience has demonstrated excellent efficacy and safety profiles for endovascular robotic technology in treating disease of the arterial tree. Catheter-based robotic systems confer clear technical advantages with regards to precision and stability of intravascular navigation, enhancing the delivery of existing therapeutic interventions, as well as enabling exceptionally challenging manipulations that are otherwise unfeasible with conventional methods. Radiation reduction is another important advantage of robotic technology. 
 
Use of intravascular robotic technology has been limited to a few specialist centres so far, with experience currently in the early clinical stages. The high cost of the technology will likely be a barrier to future uptake of endovascular robotic platforms. Whether the potential advantages from improved outcomes, reduced hospital stay and staff safety can neutralise this cost remains to be seen. Further clinical evaluation is required to target procedures and populations that will benefit from this novel technology.
 
References
  1. Bonatti J et al. Robotic technology in cardiovascular medicine. Nat Rev Cardiol 2014;11(5):266–75.
  2. Riga CV et al. Robot-assisted fenestrated endovascular aneurysm repair (FEVAR) using the Magellan system. J Vasc Interv Radiol 2013;24(2):191–6.
  3. Hansen Medical. Press Releases. 2015; Available at: http://investor-relations.hansenmedical.com/phoenix.zhtml?c=202676&p=iro…. Accessed October 28th, 2015.
  4. Bismuth J et al. Feasibility and safety of remote endovascular catheter navigation in a porcine model. J Endovasc Ther 2011;18(2):243–9.
  5. Riga CV et al. The role of robotic endovascular catheters in fenestrated stent grafting. J Vasc Surg 2010;51(4):810–19.
  6. Riga CV et al. Evaluation of robotic endovascular catheters for arch vessel cannulation. J Vasc Surg 2011;54(3):799–809.
  7. Rafii-Tari H et al. Reducing contact forces in the arch and supra-aortic vessels using the Magellan robot. J Vasc Surg 2015.
  8. Riga C et al. Initial clinical application of a robotically steerable catheter system in endovascular aneurysm repair. J Endovasc Ther 2009;16(2):149–53.
  9. Lumsden AB et al. Robot-assisted stenting of a high-grade anastomotic pulmonary artery stenosis following single lung transplantation. J Endovasc Ther 2010;17(5):612–6.
  10. Carrell T et al. Use of a remotely steerable “robotic” catheter in a branched endovascular aortic graft. J Vasc Surg 2012;55(1):223–5.
  11. Bismuth J et al. A first-in-man study of the role of flexible robotics in overcoming navigation challenges in the iliofemoral arteries. J Vasc Surg 2013;57(2 Suppl):14S–9S.
  12. Cochennec F et al. Feasibility and safety of renal and visceral target vessel cannulation using robotically steerable catheters during complex endovascular aortic procedures. J Endovasc Ther 2015;22(2):187–93.
  13. Rolls AE et al. Robot-assisted uterine artery embolization: a first-in-woman safety evaluation of the Magellan System. J Vasc Interv Radiol 2014;25(12):1841–8.
  14. Riga CV, Bicknell CD. The Magellan Robotic System Is Valuable For FEVAR, Carotid And Embolization Procedures. Presented at the 2015 Veith Symposium.
  15. Li MM et al. Occupational Radiation Exposure During FEVAR: A Stage-By-Stage Analysis. Presented at the ESVS Annual Meeting 2015.