Abstract
Remote catheter navigation to perform cardiac ablation can offer improved and stable catheter movement, as well as reaching locations that might be difficult to reach manually. Remote navigation systems employ either electromagetic or electromechanical technoloqies to help navigate a variety of ablation and mapping catheters inside the heart chambers. Each system has both advantages and disadvantages with substantial variation in the cost, learning curve, and procedure applications. This chapter provides a description and comparison of the four currently developed remote navigation systems, namely the Amigo Remote Catheter System, the Sensei Robotic System, the Niobe Magnetic Navigation System, and the Catheter Guidance Control and Imaging.
Keywords
magnetic, remote catheter navigation, robotic
Key Points
- •
Remote catheter navigation systems currently comprise electromagnetic and electromechanical technologies. Four remote systems are currently available.
- •
Each navigation system has both advantages and disadvantages with substantial variation in the cost, learning curve, and procedure applications.
- •
Potential advantages of remote navigation system are reduced operator radiation exposure and physical stress, improved catheter stability, enhanced patient safety, and automated mapping (in some instances) and catheter navigation.
- •
Remote catheter navigation systems have not yet been demonstrated superior to manual navigation in procedural success or total procedure times, although fluoroscopic times are generally shortened.
Introduction
The field of electrophysiology (EP) has evolved significantly over the last 3 decades. Before the advent of ablation procedures, EP procedures were diagnostic studies. These were usually tedious and time consuming, but with catheters remaining stationary in specific cardiac locations for the majority of the procedure. With the development of various ablation techniques, therapeutic endeavors involved precise, deliberate, and frequent catheter movements. Throughout this progression and increased complexity, procedure duration has increased and manual dexterity requirements have become ever more important. All of this was occurring in an environment that involves standing for hours in a lead apron, in a room with significant radiation exposure. The length of time required to master the skills and the physical toll from the day-to-day wear are onerous. The concept of remote catheter navigation has the advantage of allowing the operator to perform the procedures while sitting, away from the radiation source. Furthermore, robotic or other nonmanual manipulation techniques may theoretically offer improved and stable catheter movement as well as either shortening the learning curve or reaching locations that might be more difficult to reach manually. This chapter provides a description and comparison of four currently developed remote systems, namely, the Amigo Remote Catheter System (Catheter Robotics, Mount Olive, NJ), the Sensei Robotic System (Hansen Medical, Mountain View, CA), the Niobe Magnetic Navigation System (MNS; Stereotaxis, St. Louis, MO), and the Catheter Guidance Control and Imaging (CGCI; Magnetecs, Inglewood, CA).
Amigo Remote Catheter System, Catheter Robotics
Amigo ( Fig. 8.1 ) is a remote catheter manipulation system composed of a robotic arm mounted directly on the railing of the EP fluoroscopy table connected to a wired controller ( Fig. 8.2 ). Unlike other systems, Amigo incorporates minimal additional hardware beyond the equipment required for a standard manual procedure. Because it is self-contained, compact, and does not require calibration, Amigo can be moved from one room to another with relative ease. This system is an open-platform system that is designed to accommodate bidirectional catheters with the Blazer (Boston Scientific, Marlborough, MA) or EZ Steer (Biosense Webster, Diamond Bar, CA) handle platform. The catheter to be robotically controlled is placed on the docking station and is driven by the wired controller, which may be up to 30 m (100 ft) from the patient. Manual catheter movements are mimicked robotically at the bedside catheter using the controller, which emulates a bidirectional EP catheter handle. Unlike other technologies, only the catheter and a standard sheath are inside the patient. Catheter movements are distilled into three basic actions, namely, catheter-tip deflection, rotation, and advancement/withdrawal. Catheter-tip deflection is achieved by placing the catheter handle into the Amigo docking station, which controls the bidirectional steering element. Any deflection command performed on the controller is duplicated with the catheter through the docking station. Use of the catheter tension knob is not required as the system can hold a precise position indefinitely. Rotation of the catheter is accomplished by twisting the tip of the controller. This command causes the turret and the catheter to rotate. Because the nose cone and track of the Amigo do not actually rotate, rotation is not impeded by sheath rotation. Finally, catheter advancement and withdrawal are performed by pressing buttons on the side of the controller. This command causes the docking station to advance or withdraw on command along the track of the Amigo system at a rate of 13 mm per second (0.5 inches per second). Because Amigo manipulates only the mounted catheter, sheath placement is identical to that of a manual procedure. To avoid unintended catheter movement, an infrared (IR) beam and a receiver are incorporated into the controller. Only commands that are performed by the controller while being held by the operator (thereby interrupting the IR beam) are actuated. The Amigo does not further integrate into a mapping system. Therefore all 3-dimensional mapping products are used in an identical fashion to that of a manual procedure.
Sensei Robotic System, Hansen Medical
The system consists of two primary components, namely, the Sensei Robotic System and the Artisan Extend Control Catheter, a remotely controlled steerable sheath ( Fig. 8.3 ). The physician remotely directs the movement of the steerable sheath through the Sensei Robotic System—an electronically controlled mechanical system for remotely controlling the Artisan. The Sensei consists of a physician workstation, an electronics rack, and a patient-side remote catheter manipulator (RCM; Fig. 8.4 ). The system allows the clinician to direct the catheter tip to a desired intracardiac location based on visual feedback from 3-dimensional maps, fluoroscopic images, and intracardiac echocardiography images while being seated at the workstation. The RCM electromechanically manipulates the steerable guide catheter in response to commands received from the physician through a special 3-dimensional joystick (intuitive motion controller, or IMC) at the physician workstation (see Fig. 8.4C ). The basic principle of the system is that operator input is intuitive relative to an image in the navigation window monitor, which is in the center of the monitor console. The Artisan sheath is a pull wire–actuated open-lumen steerable guide sheath system. It is comprised of a flexible inner guide sheath with an inner diameter of 8 F and steerable outer guide sheath that fits through a standard 14 F hemostatic introducer. The Artisan attaches to the RCM through a sterile drape barrier and the RCM in turn actuates the catheter pull wires in response to commands from the physician. The Artisan is a guide sheath and is not capable of therapy or diagnostics on its own. Rather, any commercially available ablation catheter can be placed into the Artisan, with just the distal two electrodes extending beyond the inner guide tip. The Artisan can articulate in any direction up to 275 degrees, with a minimal working curve diameter of 30 mm ( Fig. 8.5 ). Of note, in 2016 Hansen Medical was acquired by Auris Surgical Robotics (San Carlos, CA), and, as of June 2017, the future of this technology is uncertain.
Niobe Magnetic Navigation System, Stereotaxis
Unlike the two previously discussed technologies, the Niobe is a remote magnetic navigation system (MNS) that provides robotic catheter guidance capability. Controlling the direction of the catheter is accomplished by changing the direction of a magnetic field within the patient’s heart. The system does this by moving large permanent magnets located on either side of the patient during a cardiac procedure ( Fig. 8.6 and 
on Expert Consult). The magnetic field generated with this system approaches 0.1 T and controls proprietary irrigated and nonirrigated ablation catheters that integrates fixed magnets on the shaft near the tip, currently produced by Biosense Webster and Biotronik (Berlin, Germany). The Niobe system provides a discrete control whereby the operator sets a desired direction for the catheter and the system responds by calculating the motion requirements and then executing the request by changing the magnetic field orientation. Because the magnetic fields are changed by mechanical movements, there is a delay between the operator command and the catheter movement within the heart. The amount of catheter advanced into the patient is controlled by a motor that advances and withdraws the catheter as desired. These two means of manipulation allow for precise control using magnetic pull with minimal axial catheter force ( 
on Expert Consult). In addition to the Niobe MNS, Stereotaxis has developed Vdrive, a robotic navigation system that provides the physician the ability to control diagnostic catheters remotely from the control room. Control of the diagnostic catheters is conducted entirely at the proximal end by actuating the catheter standard handle controls through a series of electromechanical actuators. There are four axes of motion and, depending on the disposable set installed, can control actions such as advancement/retraction, rotation, loop sizing, and deflection of different catheters. The disposable portion of the system includes a set of handle clamps designed to interface with the device’s handle, a sterile drape that covers the hardware portion of the system, and (in most instances) a tube, which provides support to the proximal section of the device.
Catheter Guidance Control and Imaging, Magnetecs
Like Niobe, the Catheter Guidance Control and Imaging (CGCI) system is a magnetically based navigation product that uses eight coil-core electromagnets arranged in a semispherical array around a patient’s torso ( Fig. 8.7 ). The magnet design includes a specially shaped ferrous ring at each magnetic pole face intended to focus the magnetic flux toward the center of the chest ( Fig. 8.8 ). Magnetic shielding encases the structure to minimize magnetic interference of surrounding objects. This avoids the need for any significant magnetic shielding in the room during configuration and installation. Furthermore, unlike permanent magnets, this device is magnetically inert when powered off. When in use, the system design results in a shaped (lobed) magnetic field in a 15 × 15 × 15 cm (6 × 6 × 6 inch) cube in the heart with a magnetic field strength of 0.14 T. This system is designed to control a 7 F, irrigated flexible ablation catheter with an integrated magnet located at the tip (Bernoulli Cool-Flow; Figs. 8.9 A and B ). The unique magnetic field design is intended to better facilitate catheter contact with tissue during the procedure; moreover, operator commands are actuated nearly instantaneously. The system is designed with full integration with the EnSite NavX electroanatomic mapping system (St. Jude Medical, St. Paul, MN), and it includes a proprietary transseptal sheath (Lorentz-Active sheath; see Fig. 8.9C ). This addition adds five platinum electrodes at the sheath tip as reference points to reduce motion inaccuracies from coronary sinus reference electrodes alone. Control of the system involves either operator-controlled guidance of a joystick, which directs catheter movements through the magnetic field direction or can be controlled in an automated mode based on target lesion sets applied directly to the 3-dimensional map ( Fig. 8.10 ). So far, this system has been validated only in animal studies.
