Catheter ablation for atrial fibrillation (AF) has emerged in the last several years as an important strategy in the treatment of this arrhythmia.¹ With the expected rise in the number of AF patients as the population ages, the role of catheter ablation is expected to become more prominent in the future. There are many techniques in AF ablation, ranging from anatomical ablations encircling the pulmonary veins and making linear ablation lesions, as well as those techniques that target specific electrophysiologic signals such as pulmonary vein potentials or fractionated electrograms, or those that attempt modification of the vagal innervation into the heart.^2–4 Despite the differences in techniques, it is clear that the shared goal is to achieve adequate tissue ablation as safely and quickly as possible, and in doing so, increase the success rate of AF ablation.

Figure 1.

Sensei System.

       Current catheter systems for atrial fibrillation ablation include standard (irrigated or non-irrigated) radiofrequency catheters. In addition, there are catheters that utilize other energy sources, which are currently being investigated for use in the United States. One of the major challenges in utilizing the current standard catheter systems is the potential difficulty when navigating the catheter to different ablation target sites in the left atrium. Variations in left atrial and pulmonary vein anatomy and size can make the task of navigation more challenging. Current catheter systems utilize a pull wire technology that affects a curve on the distal end of the catheter. By making different curves and changing the torque applied to the catheter, the catheter can be maneuvered in the target area. Limitations of this include that most catheters come with a fixed radius of curvature, and the delivery of torque can be impeded by use of the long sheath that is required to enter the left atrium after transseptal puncture. If another catheter curve is needed during a procedure, a different catheter may be needed. Deflectable sheaths may also be used in conjunction with the catheter, although these also have a fixed radius and often do not have a wide range of motion available. Catheter stability and contact with current catheter systems can often be a challenge as well, because there is no objective way to assess catheter tissue contact that is currently available. In addition, the sheaths that are used for stability and to maintain good contact may impact catheter maneuverability.
       Recently, Hansen Medical’s Robotic Catheter Control System was cleared by the U.S. Food and Drug Administration to “facilitate manipulation, positioning and control of mapping catheters during electrophysiology procedures in the atria of the heart.” In Europe, regulatory clearance is extended to include ablation of arrhythmias as well. This robotic catheter control system is compatible with current catheters (of less than 8.0 French), ablation systems and advanced mapping systems. Robotic control of the distal catheter tip allows 270 degrees of mobility and maneuverability with six degrees of freedom. Additionally, because the catheter can be maneuvered remotely, exposure to fluoroscopy can be minimized by the operator, an important detail for physicians who perform a large number of ablation procedures. In this article, I will discuss how robotic catheter control can be a beneficial feature for EP labs.

Figure 2.

Robotic Arm with Artisan Catheter.

About the Technology
       Hansen Medical’s Robotic Catheter Control System was developed over the last several years for use in electrophysiology mapping and ablation procedures. The system is comprised of the Sensei^™ Robotic Catheter System (Figure 1) and the Artisan^™ Control Catheter (Figure 2). The workstation portion of the Sensei System is the physician interface. At this interface, the operator can control the direction of the Artisan Catheter by manipulating a specialized interactive motion controller. Motion of the controller is then translated to motion of the Artisan Catheter tip. This can be set by the user for translation of motion in a 2:1 fashion, or differently if so desired. The Sensei System interface also allows visualization of fluoroscopy, intracardiac ultrasound images, three-dimensional (3D) mapping system images and real-time electrograms.
       The Artisan Catheter is comprised of an outer sheath that allows some deflection and an inner robotically-controlled guide catheter that is maneuverable in all directions. A standard ablation catheter from any manufacturer (including those compatible with electroanatomical mapping systems) is placed within the lumen of the Artisan Catheter. The steering mechanism of the ablation catheter is no longer used as the catheter is then steered via the Sensei system.

Figure 3.

Artisan Catheter only.

Study Data
       An initial study examining the utility of the Hansen Robotic Catheter Control system in ex vivo hearts determined that the ability to navigate and make precision movements was faster than with a standard catheter system.⁵ Further experience using the system in animal studies demonstrated the safety and feasibility of mapping and ablation in all four cardiac chambers, as well as for transseptal puncture.^6,7 In addition, the system was demonstrated to be compatible for use in tandem with electroanatomical mapping systems and 3D images of the heart.^8,9
       More recently, the safety and feasibility of using the system in humans undergoing mapping and ablation of atrial tachyarrhythmias (including atrial fibrillation) has been demonstrated.^10,11 In one study, seven patients underwent mapping of the right atrium using an electroanatomical mapping system. Two of these seven patients also underwent mapping of the left atrium. Another two patients had successful ablation of supraventricular tachycardia.¹¹
       Another study evaluated the ability of the Robotic Catheter Control System to navigate to specific targets in the right and left atrium in patients undergoing ablation. In this study, the mean time for the operator to maneuver to specific sites was only 2.1 minutes.¹⁰
       It is important to note that use of the Robotic Catheter Control System does impact on tactile feedback to the operator; this has led to the concern that the lack of tactile feedback may have safety implications. However, Hansen Medical recently added to their Robotic Catheter Control System the ability to detect, measure and display force against the catheter tip. This new ability not only functions as an added safety measure, but also adds a new dimension to the use of contact force in optimizing lesion characteristics.

Figure 4.

Navigation window of the Sensei Robotic Catheter system showing the combined display of fluoroscopy, ICE, and IntelliSense force sensing data.

About IntelliSense^™
       IntelliSense Fine Force Technology is a unique method to assess the amount of force affecting the catheter. Force load cells are located at the proximal end of the catheter; these cells are able to measure the force in grams transmitted along the shaft of the catheter as a result of catheter tissue contact. The amount of catheter tissue force is then graphically displayed on the monitor of the Sensei System. This gives immediate feedback to the operator throughout the duration of the procedure. Thus, the physician is able to set a gram threshold whereby a visual indicator is invoked when the amount of force may be higher than that desired.
       In addition to the additional safety measure that IntelliSense provides, this information may also be used to optimize lesion size and map quality. In a recent animal study, ablation in the left and right atrium was attempted using a different catheter tissue force in each animal (10 grams vs. 30 grams), while keeping the amount of energy used stable.¹² Lesion geometry and transmurality were then measured. There was an increase not only in lesion size with increased pressure of 30 grams, but the percent of lesions that were transmural also increased regardless of the amount of energy used (20 watts or 30 watts). This study suggests that by modulating catheter tissue interface force — something previously impossible to do — we may be able to optimize lesion size, transmurality and safety. Further study in this area will help understand the best utility for this added feature.
       Another recent animal study found value in the use of IntelliSense for map creation as well. Electroanatomical maps (EAM) were created using IntelliSense pressure sensing as a guide. These were then compared to other three-dimensional CTs to assess the actual tissue mismatch. Maps created using more than 10 grams of pressure showed significant mismatch, particularly at forces above 18 grams of pressure. By creating maps using 5-10 grams of pressure, EAM distortions can be minimized.¹³

Conclusion
       Hansen Medical’s Robotic Catheter Control System can add precise catheter control, stability and maneuverability to electrophysiology mapping and ablation procedures. These features, coupled with the added safety of IntelliSense and the potential of lesion and map optimization using catheter tissue interface pressure, make robotic catheter control an attractive option for the modern EP lab. This technology may help improve the ability of less experienced operators to perform complex electrophysiology procedures, and at the same time, reduce fluoroscopy exposure.


Editor’s Note: This article was peer reviewed by one or more members of EP Lab Digest’s editorial board.