In an effort to develop an Electrophysiology program that offers the highest possible level of care to our arrhythmia patients, The Minneapolis Heart Institute at Abbott Northwestern Hospital is dedicated to investigating new ablation technologies and techniques. For years, we have found the three-dimensional (3-D) mapping and navigation capabilities of the EnSite^® System (St. Jude Medical, St. Paul, Minnesota) quite useful for facilitating ablation of complex arrhythmias in the EP lab.

Figure 1.

William Katsiyiannis, MD, Vanessa Ervin, RCIS, EP Technician, Kerri Leverence, EP Technician, and Jayme Matelski, NASPE Testamur, EP Supervisor. Not pictured: Daniel P. Melby, MD.

       With the advent of the Stereotaxis remote catheter navigation technology (Stereotaxis, Inc., St. Louis, Missouri), we saw an opportunity to improve our ability to perform complex ablation procedures while maximizing the capabilities of an advanced 3-D mapping system. By reducing the risk of catheter perforation, limiting fluoro exposure and improving accuracy, these two systems provide a unique marriage of capabilities for our EP lab.

A Simple, Straightforward Combination
       We began using the two systems together in January 2006, when the Stereotaxis catheter was approved for use. Both the EnSite Array non-contact catheter and EnSite NavX navigation and visualization technology have been in use at the Minneapolis Heart Institute/Abbott since the products were available. The EnSite System and Stereotaxis have worked together seamlessly from day one, providing a great union of clinical accuracy, improved safety and procedural efficiency.
       Due to their inherent stiffness, traditional electrophysiology catheters can stretch tissue and cause distortion of cardiac structures. This can cause false space when creating chamber geometry. One of the unique performance characteristics of the Stereotaxis catheter is that it’s a very floppy, forgiving catheter. It has become evident that the geometries created by magnetic manipulation are actually more demonstrative of the atrial structure because the softer catheters reduce the potential for “tenting” of the atrial tissue.

Figure 2.

Dr. Katsiyiannis views detailed EnSite cardiac geometries alongside the Stereotaxis navigation system.

Better for Patients, Better for Staff
       Stereotaxis catheters depend on magnets to move rather than internal wires, so they do not have the same requirements for catheter pushability and torqueability to achieve and maintain position. With this new method of magnetic catheter manipulation, we can access difficult areas of the chamber quickly, safely and easily, which helps create a clearly defined chamber model. Preset and memory features of Stereotaxis navigation also allow for quick access and return to difficult locations.
       The combination of a catheter with less potential for perforation and the ability of the EnSite System to quickly capture anatomic detail has also allowed us to achieve a reduction in overall procedure and fluoro time. In our practice, using traditional catheters and standard mapping techniques, the average ablation patient required approximately 60 minutes of fluoroscopy time. However, the combination of the advanced systems has allowed us to reduce fluoro time to approximately 15 minutes per patient. Most of the fluoro time is comprised of initial catheter placement and transseptal puncture. Once ablation begins, we rely entirely on the EnSite System model. This is a tremendous benefit to our staff, dramatically reducing their total fluoro time, especially when you consider that we are often performing 1–2 atrial fibrillation ablation procedures per day.

Figure 3.

An EnSite System geometry created using Stereotaxis.

       Along with a reduced reliance on fluoro, multiple EnSite System monitors allow all members of our staff to view the procedure. At a minimum, catheter movement is being observed by the physician on the Stereotaxis controls, the EnSite System operator, and the person manning the RF generator. More eyes on the catheter mean less chance of ablating in an inappropriate location and less risk for the patient.

New and Unique Capabilities
       Both Stereotaxis and the EnSite System offer unique capabilities to facilitate more efficient and effective procedures. For example, the Stereotaxis system offers a “bulls eye” feature, where at the push of a button the catheter will spin in a programmable radius to define a chamber or pulmonary vein. The EnSite System can also gather mapping points continuously as the Stereotaxis catheter progresses on its radial path around the vein ostia, rather than capturing only the 10 points provided by a traditional circular mapping catheter. This feature allows us to better map and isolate the ostia of the pulmonary veins, in many cases making it possible to avoid using an additional catheter, a second sheath, and performing a second transseptal puncture.

Figure 4.

Figure 5.

Figures 4 and 5. Multiple EnSite monitors allow all team members to view catheter placement throughout the procedure.

Things to Remember
       When bringing together remote navigation and 3-D mapping, begin by using typical views. It’s challenging to tell the computer where to go if you haven’t orientated your geometry within the navigation system in a way that corresponds well to the mapping system. Begin by orienting the EnSite System to real RAO and LAO, then orient the Stereotaxis system in the same manner. This way, when you move the Stereotaxis navigation to the right, the catheter moves to the right.
       By adding the esophagus to the 3-D geometry, it is possible to monitor catheter proximity to the esophagus without significant use of fluoroscopy.

Figure 6.

By adding the esophagus to the 3-D geometry, it is possible to monitor catheter proximity to the esophagus without significant use of fluoroscopy.

       It can also prove very useful to create a model of the esophagus using an EP catheter, enabling you to add this structure to your 3-D geometry. We then place a temperature probe in the esophagus and monitor for temperature increases when nearing the esophagus. Because we can depend on the detail of the map to show clearly when we’re approaching the esophagus, this has also contributed to a significant reduction in flouro use.
       Finally, understand that there is a learning curve to working with these systems. It takes time in the beginning, but there is a payoff. In less than one year of use, our team has reduced the average atrial fibrillation ablation time by 1 hour.

Experience with Remote Navigation and 3-D Mapping:

-Charles C. Gornik, MD, Director of EP Services, Minneapolis Heart Institute, Abbott Northwestern Hospital The catheter control and flexibility of Stereotaxis and the high-detail visualization of the EnSite System combine to provide value that neither can offer individually. The magnetically manipulated catheter is able to move in small increments with great precision, but without an equally precise representation of the catheter in anatomy, this benefit is lost. Previous versions of the EnSite System sometimes had the potential to show “false space”, resulting from curves or ridges in the patient’s anatomy. However, with Version 6 software and its ability to build geometries with multiple surfaces, we can create cardiac models that rival a CT or MRI scan in detail. While these attributes are useful in any complex ablation case, they have proven indispensable for some of our more complex left atrial ablation procedures. Recently a patient was referred for ablation who suffered from severe Pectus, which squeezed his heart back against his spine. We attempted to map the left atrium by hand, but the spine kept forcing the catheter to go anterior. Using the Stereotaxis system and the multiple surface capabilities of the EnSite System, we were able to direct the tip of the catheter into each vein and create a geometry that equaled the MRI for detail. Thanks to accurate navigation and localization of an extremely flexible catheter, the patient was treated successfully and continues to do well. As we continue to strive for an improved level of care for our patients, it is important to be able to place lesion sets precisely and reproducibly. Only with confidence in our navigation and lesion placement will we be able to refine our ablation procedure for patients with atrial fibrillation and other complex arrhythmias. The combination of remote catheter navigation and 3-D multiple surface mapping will be important to achieving that confidence as we move forward in that effort.

Figure 7.

This unique 3-D cardiac geometry was only possible by combining the capabilities of Stereotaxis and the EnSite System.