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G. Joseph Gallinghouse, MD; Luigi Di Biase, MD, PhD; Andrea Natale, MD1

Introduction

Ablation has become a common method of treating AF, as antiarrhythmic drug therapy is relatively ineffective and fraught with side effects. While there have been significant advances in technology that facilitate safe and effective application of ablation lesions, manual catheter navigation remains essentially unchanged since the mid-1990s. Over the past several years, remote catheter navigation systems have emerged that allow for refined catheter positioning and contact titration relative to manual navigation. There are also advantages to the operator, allowing ablation from an ergonomically favorable seated position, removed from the radiation field. Our group at the Texas Cardiac Arrhythmia Institute at St. David’s Medical Center (Austin, TX) has amassed the world’s largest experience in robotic catheter navigation. This chapter describes our approach.

Background

For those of us in cardiac EP training programs during the mid-1990s, the concept of taming AF with ablation seemed to be the proverbial “Holy Grail.” We fondly recall the excitement of eliminating accessory pathway-mediated tachycardias and AV nodal reentry. The typical flutter circuit had just been defined, and lesions at the tricuspid isthmus would terminate the arrhythmia—to our delight. However, AF was our nemesis. Then, Haïssaguerre and colleagues¹ published the seminal observation in 1998 that the great majority of AF triggers resided in the PVs, finding that the arrhythmia could be suppressed by targeting these sites with ablation. This led to intensive investigation of the optimal approach to elimination of these triggers, ultimately evolving to the current “PV isolation” procedure—of which there are several variations.^2–8

The past decade has seen tremendous strides in the development of technology to facilitate safe and effective ablation of the AF substrate. The medical device industry, driven by market opportunity and competition, has quickly provided tools that allow the modern electro-physiologist to approach even the most complex arrhythmias. Advanced 3-dimensional (3D) electroanatomical mapping systems allow the operator to reconstruct the anatomy of the chamber of interest in real time and to track electrical activation on a beat-by-beat basis.9 Availability of voltage mapping with these systems has facilitated ventricular tachycardia ablation and assessment of PV isolation. The development of ICE provides continuous visualization of catheter location relative to important structures, facilitates transseptal catheterization, and allows early detection of ablation-related complications such as pericardial tamponade.^10,11 However, lagging behind has been improvement of the navigational capabilities of the primary therapeutic tool—the ablation catheter itself.

Ablation catheters have been enhanced with tip irrigation for cooling, which has advantages in lesion formation and avoidance of char.¹² Contact force sensors have been added to allow for continuous assessment of catheter pressure against the myocardium. This is a major development given that tactile feedback and visual cues are a poor gauge for the operator of proximity to tissue targets. Remarkable, however, is the fact that the steering mechanisms of modern ablation catheters are little different than those found in catheters from the mid-1990s.^13–16 Even though we are now required to create much more complex lesion sets covering large geometric areas, the manual ablation catheter is still limited to uni- or bidirectional movement using pull wires.

Recently, remote navigation systems have emerged that allow movement of the ablation catheter with computer-guided precision not attainable manually. Navigation may be linked to a 3D mapping system that provides intuitive catheter “driving” based on the real-time anatomy generated during the case. Very fine contact titration can be performed during ablation, which may allow delivery of more effective RF energy to tissue with reduced power requirements.

There are two current commercially available remote navigation systems. One utilizes application of magnetic field vectors to a proprietary catheter (Stereotaxis, St. Louis, MO), and the other maneuvers standard ablation catheters robotically (Hansen Medical, Mountain View, CA).^17–30 This review will describe our experience with the robotic system for ablation of AF, which is the most extensive in the world to date.

As with any new medical technology applied to a challenging clinical problem, there are individual and collective learning curves that must be overcome to achieve optimal utilization—both from safety and efficacy standpoints. The manufacturer may make recommendations as to the intended operation of the system, but ultimately it is the responsibility of the operator to determine “best practices” with regard to the care of patients. Robotic catheter navigation is no different.

After clinical trials in Europe, the first installation of a Hansen system in the U.S. occurred at the Cleveland Clinic in May 2007, followed by St. David’s Medical Center in Austin, TX, in September of that year. Our group endeavored to learn the system quickly and began to perform AF ablation procedures in high volume immediately. We accepted the concept that our early experience would be relatively time consuming, but the hope was that repetitive use would lead to rapid mastering of the technology. This in fact was the case, and within the first 30 cases, our ablation times to achieve clinical endpoints were equivalent to those cases performed manually.

In an attempt to accelerate “ascent of the learning curve” through the shared experience of many operators, several users’ group meetings were held in 2008 and 2009. This allowed us to quickly determine the most successful approaches to various technical aspects of the robotic ablation procedure. While the methods have thus become fairly standardized, there are slight variations from center to center.

The “Austin approach” will be detailed below.

Description of the Hansen System

The Hansen robotic catheter navigation system allows remote manipulation of an ablation catheter utilizing computer-driven input to a bedside robotic arm. After placement of the robotically driven catheter in the chamber of interest, the operator sits at a console with controls that input commands to the catheter via the robotic arm (Figure 28.1).

The system consists of two primary components, the Sensei Robotic Catheter System and the Artisan Guide Catheter, a remotely controlled steerable sheath (Figure 28.2). The physician remotely directs the movement of the Artisan Guide Catheter through the Sensei Robotic Catheter System—an electronically controlled mechanical system for remotely controlling the Artisan. The Sensei is comprised of a physician workstation, an electronics rack, and a patient-side Remote Catheter Manipulator (RCM) (Figures 28.1 and 28.2).

The system allows the clinician to direct the catheter tip to a desired intracardiac location based on visual feedback from 3D electroanatomic maps, fluoroscopic images, and ICE images while seated at the workstation. The RCM electromechanically manipulates the steerable guide catheter in response to commands received from the physician through a special 3D joystick (Intuitive Motion Controller, or IMC) at the physician workstation. A 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. For example, if the navigation window is an LAO fluoroscopic image of the LA, movement to the right with the IMC will direct the Artisan toward the lateral wall, and pushing the IMC away from the operator (or “into the monitor”) will direct it toward the posterior wall.

The Artisan Guide Catheter is a pull-wire-actuated open-lumen guide catheter. The inner lumen is 8-Fr diameter and the guide catheter fits through a standard 14-Fr 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 catheter and is not capable of therapy or diagnostics on its own. Rather, commercially available ablation catheters are placed into the Artisan, with just the distal two electrodes extending beyond the Artisan tip.

The Artisan can articulate in any direction to 270°, with a minimal working curve diameter of 30 mm (Figure 28.3; Video 28.1).

Introduction of the Artisan Catheter

In the majority of laboratories, the robotic arm is positioned on the patient’s left side, and therefore the Artisan catheter is inserted via the left femoral vein. This leaves the right side unobstructed for the operator when manipulation of a second mapping catheter or ICE catheter is required. Early-experience placement of the Artisan from the left was occasionally problematic, particularly in a tortuous iliac vein, given the size and stiffness of the catheter relative to typical EP equipment. There were reports of retroperitoneal bleeding complications attributed to iliac tears.²²

The solution was to insert a long (30 cm) sheath under fluoroscopic guidance extending into the IVC. The Artisan was then placed through the long sheath, with the relatively soft ablation catheter approximately 5 cm beyond the tip of the inner guide. Once safely in the IVC, the Artisan could be manually advanced to the RA under fluoroscopic guidance, leading with the steerable ablation catheter. The Artisan could then be advanced over the fixed ablation catheter into position in the low RA ( Video 28.2).

Occasionally, we find that insertion of the long introducer sheath to the IVC is difficult depending on the left iliac anatomy. Shaping the tip of the sheath/dilator with a 30° bend and use of a stiff wire (Amplatz) will usually facilitate this step. However, we are occasionally required to remove the dilator and insert our 10-Fr steerable ICE catheter into the sheath in the distal iliac vein (Figure 28.4; Video 28.3).

The ICE catheter is then directed into the IVC and used as a “rail” for the long sheath. We have yet to encounter a case where the left-sided Artisan access site had to be abandoned, but ultimately the access site could be shifted to the right if necessary. To demonstrate the course of the left iliac vein, we always insert a CS catheter from the left before inserting the long sheath.

Transseptal Access

Robotic LA ablation requires placement of the Artisan catheter through a transseptal puncture site, as with any other such procedure. Even if a PFO is present, transseptal access obtained via puncture as the ideal crossing is at the antero-inferior aspect of the fossa. This provides an ideal angle of attack for ablation near the right PVs.

Our practice is to utilize an SL1 (St. Jude Medical, St. Paul, MN) or similar sheath, along with a Brocken-brough needle, to access the LA with ICE guidance. We then place a circular mapping catheter (Lasso, Biosense Webster, Diamond Bar, CA) into the LA via the sheath and carefully build the geometric reconstruction of the chamber using the Endocardial Solutions NavX 3D electroanatomical mapping system (St. Jude Medical) or with the CARTO 3D Mapping System (Biosense Webster). After the geometric map has been obtained, the Lasso is removed and a guidewire placed through the transseptal sheath into a left PV for support. The sheath is then withdrawn into the RA, which leaves its transseptal access site available for passage of the Artisan.

With a guidewire marking the location of the fossa ovalis puncture site, along with the trajectory from RA to LA, safe transseptal placement of the Artisan is relatively simple. We robotically position the Artisan-ablation tip near the fossa using both fluoroscopy and ICE guidance. Using orthogonal fluoroscopic views, the ablation tip is robotically aligned to the guidewire and then carefully “driven” through the puncture site until saline echo contrast is seen in the LA ( Videos 28.4 and 28.5). The outer guide can be advanced for support if there is any difficulty passing the inner guide into the LA, as, for example, in the case of a thickened fossa.

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