Initial Experience with the Hansen Medical Sensei Robotic Catheter System

Atrial fibrillation (AF) ablation has emerged as a vital tool in the management of this frequent and challenging atrial tachyarrhythmia. Success has been achieved across the entire spectrum of cases, from paroxysmal to permanent. More advanced electrophysiology laboratories across the country are engaging in AF ablation on a regular to frequent basis, and more electrophysiologists are finding this to be the most common ablation that they perform. However, the procedure is both time and resource intensive. Being able to quickly manipulate the ablation catheter to all target sites while maintaining stability and minimizing fluoroscopy is a challenge. Manual control of the catheter requires considerable skill, which is largely dependent on the experience of the operator. Frequent performance of these complex cases may also result in significant operator fatigue. In recent years, robotic catheter guidance systems have become available to facilitate this process. There are two types of systems currently in use. We wish to describe our initial experience with Hansen Medical’s Sensei X Robotic Catheter System. Background Banner Heart Hospital is a 111-bed specialty hospital that focuses exclusively on cardiovascular disease. The electrophysiology program has evolved and expanded over the decade that the hospital has been in existence. We now have two dedicated electrophysiology laboratories, both of which have dedicated staff and mapping systems. As of July 2010, Banner Heart Hospital has performed 953 electrophysiology procedures, which include atrial fibrillation, atrial flutter, AV node and supraventricular (SVT) ablations, since the beginning of the year. We continue to see an increase in the number of AF patients who present to our institution on an emergency and outpatient basis each year, and this poses a significant challenge because of the impact on patient health and well-being, as well as cost for care. To that end, we have developed an atrial fibrillation ablation program at Banner Heart Hospital. The initial strategy was to incorporate the use of three-dimensional mapping w/CT guidance to allow for pulmonary vein isolation and administration of other lesions as indicated. We also use intracardiac echocardiography (ICE) to assist with transseptal catheterization and for monitoring of catheter position in lesion delivery. To enhance the AF and ventricular tachyarrhythmia ablation programs, we acquired and installed in June 2010 the Sensei X Robotic Catheter System (Hansen Medical, Mountain View, CA). About the System The system consists of several components. The ablation catheter is placed in a set of two guide sheaths, which are advanced through femoral venous access (14F sheath). The steerable guide sheath attaches to a remote catheter manipulator (RCM), which is positioned over the patient. The physician sits at a workstation centered around a master control panel where the Instinctive Motion Controller (IMC) is located. This is, in essence, a joystick which provides feedback to the RCM. The RCM acts on commands to advance, retract, and flex the guide sheath to allow three-dimensional motion of the ablation catheter. Controls for the RCM movement and calibration reside at the workstation. The workstation also has display screens for intracardiac electrophysiologic signals, fluoroscopy, navigational mapping, and ICE. Banner Heart Hospital Experience Before the robotic catheter system was installed at our facility, the primary electrophysiology operators initially went through training by going to an outside center with high volumes; there we were able to observe several cases being performed using the system. We then underwent hands-on training in an animal laboratory. Subsequently, the initial cases involved relatively straightforward right-sided ablations to gain some experience in catheter manipulation. As of July 2010, we have performed 13 robotic procedures using the system, including atrial flutter, atrial fibrillation, SVT and inappropriate sinus tachycardia (IST). Atrial Fibrillation Case Example The patient is a 63-year-old male with a history of paroxysmal atrial fibrillation dating back eight years. He had a history of concomitant coronary artery disease and hypertension. Prior medical treatment included beta blockers and amiodarone. He had required cardioversion on one occasion. During one period of anticoagulation withdrawal two years ago, he suffered an embolic stroke. He has since been on chronic anticoagulation. Because of persistent symptoms of dyspnea and fatigue associated with recurrent spells, he was referred for ablation. Baseline echo demonstrated borderline left atrial enlargement. TEE just prior to the procedure was negative for thrombus or smoke, but demonstrated at least moderate atrial enlargement by volume. The presenting rhythm to the lab was sinus. The procedure involved pulmonary vein isolation of all four veins. Entrance and exit block were verified post ablation and on isuprel. No additional lines were made. The patient has not experienced any recurrences of clinically manifest atrial fibrillation in the last eight weeks. Discussion We have done a total of six atrial fibrillation cases since system implementation. The majority were first-time primary atrial fibrillation patients. It was elected to begin with the most straightforward cases to try to achieve the best results during the early phase of system use. The standard approach at our lab involves intracardiac echocardiography, followed by transseptal catheterization and creation of left atrial geometry and correlation with a previously obtained CT image. We have been using a 3D mapping system (EnSite NavX, St. Jude Medical, St. Paul, MN). Subsequently, the Artisan steerable catheter system is brought across the inter-atrial septum. We then proceed with pulmonary vein isolation. Ablation energy is delivered using the ThermoCool ablation catheter (Biosense Webster Inc., a Johnson & Johnson company, Diamond Bar, CA). Roof and mitral isthmus lines and other lesions are made when indicated. The first two atrial fibrillation cases averaged 20 minutes of fluoro use with the Artisan, while the last four have seen that time cut in half. Total procedure times remain consistent to date. In atrial fibrillation ablation, the lines have to be made very effectively without gaps and have to be transmural. Manually controlling the catheter to create those lines can be quite tedious. Having this system provides the stability and precision needed to literally make those lines continuous. Being able to let go of the catheter while the energy is being delivered allows the operator to focus on more critical aspects of the case — the loss of pulmonary vein electrograms, esophageal temperature, ultrasound evidence of thrombus, etc. “This technology allows me to ablate those areas with precision and much success. I have been very pleased, particularly with its use for atrial flutter ablation. In the beginning, I was using the same amount of power in terms of watts, and I realized I should use less energy, less watts, less power. The success for each lesion is a lot clearer, more evident,” says Dr. Chan. “I think the biggest advantage of the system is that the catheter has very stable contact with tissue. Every time you create a lesion, the size of the lesion is very predictable and the lesion creation is very efficient,” notes Dr. Chan. “In my experience, the system has allowed me to ablate flutter a lot more effectively, safely, and in much less time.” “There is certainly a change in mindset involved in adopting a robotic navigation system,” adds Dr. Kaplan. Electrophysiology operators are used to hands-on catheter control, so delegating that to an electromagnetically controlled sheath system involves a leap of faith. We are used to a sense of feel to determine the correct amount of catheter contact. That is not available with the robotic system. However, the Sensei system does have a feedback mechanism called IntelliSense that offers numeric readings and vibratory feedback to help the operator. Studies have demonstrated the amount of force needed to provide optimal energy delivery and the amount which increases the risk for cardiac perforation.” There is also the challenge of having to get used to how to manipulate the catheter in three dimensions using the control handle and a virtual image of the catheter. Fortunately, the control panels include a fluoroscopic image, an ultrasound image, and the geometry created with the EnSite system. By alternating between relying on these three views, we have learned to be able to sit and relax more while concentrating on the tasks at hand. During these initial cases, we have experienced no major complications. The electrophysiology team also received extensive orientation and has become quite facile at the setup of the system. The system has been easy to learn and has certainly not increased the duration of the cases or fluoroscopy exposure. It has allowed the operators to focus on monitoring many more variables and screens, and has been a benefit in the performance of these complex ablation cases. Summary We were happy to be able to implement the use of the Sensei X Robotic Catheter System in our new state-of-the-art electrophysiology laboratories without having to retrofit in a way that would be required for use of a magnetic-based steerable system. It is our hope that as our experience grows, we will be able to reduce the total procedure time as well as fluoroscopy exposure to the patients and the team. The general rule of thumb is that rapid completion of 50 cases results in a satisfactory plateau in the learning curve. We are looking forward to the integration of this system with the EnSite Cohesion mapping system, because this will further refine manipulation of the catheter to allow for more rapid lesion delivery. We are also looking forward to development of new sheaths which will allow for ablation of other complex dysrhythmias in the future. In summary, the Hansen Medical Sensei X Robotic Catheter System has been an exciting addition to our electrophysiology program and should help to improve efficiency, making the procedure safer and more effective for our patients at Banner Heart Hospital.