Non-Contact Cardiac Mapping Has Arrived

Approximately three million people in the United States suffer from some form of supraventricular tachycardia (SVT). Many of these patients suffer from complex forms of this arrhythmia, resulting from multiple points of origin in unpredictable locations in the heart. Generally, the ability to adequately diagnose these complex tachycardias has been limited by the capability of conventional technology. Diagnostic contact catheters have frequently produced an insufficient amount of data to effectively locate, diagnose and facilitate treatment of these types of complex tachycardias. The Seton Heart Center EP lab performs an average of 55 EP studies per month. Approximately, 60% of the studies are ablations. Our lab at Seton Medical Center has recently purchased the Endocardial Solutions Non-Contact Mapping System to more effectively pinpoint the origin of these patients' arrhythmias. The Ensite 3000 ®, a non-contact, global activation, 3D image mapping system is used during complex EP studies. The greatest advantage of the system is its ability to map an arrhythmia in only one or two beats. This is especially useful with patients who are unable to tolerate rapid rhythms and cases when the arrhythmia cannot be sustained long enough for adequate analysis. The EnSite catheter has 64 laser-etched electrodes that allow accurate, simultaneous recording of the entire heart chamber (Figure 1). The EnSite catheter is placed in the chamber of interest in a low profile through a 9 French (Fr) introducer. Once appropriately positioned, the balloon is inflated with a mixture of saline and contrast to allow for easy viewing under fluoroscopy. By moving the EnSite non-contact catheter around the heart chamber, a 3D-computer model image is established using the sensed electrical potentials of the endocardium (Figure 2). A multi-color computer image is then constructed and displayed on the workstation screen. The isopotential and isochronal maps are shown on this model. The geometry and landmarks are obtained through the physician s use of a roving catheter. The EnSite 3000 System tracks the movement of the contact catheter and documents any points outside the bounds of the current model (Figure 3). The process takes approximately 5 minutes to collect a sufficient number of points, greatly decreasing the amount of time normally required to place a catheter at each site and record multiple cardiac cycles. The system permits short-duration, high-resolution mapping of an entire heart chamber allowing the hemodynamically compromised patient to have their arrhythmia mapped in a relatively short period of time. According to Texas Cardiac Arrhythmia electrophysiologist, Rodney Horton, MD, "Endocardial Solution s system will make complex cases easier and technically impossible cases possible." Dr. Horton s statement reflects the sentiments of all the physicians in his practice. Dr. Robert Canby and his partners, Jason Zagrodsky, MD, Sam Barbera, MD, and Joe Gallinghouse, MD, are dedicated to the detection and treatment of heart rhythm disturbances and are experts in the use of this advanced mapping technology. Seton s EP Lab has seen different effects on the cost per case, depending on physician preference and patient needs. Some physicians opt to include contact catheters in the study to predetermine or diagnose arrhythmias while others use only the EnSite catheter and an ablation catheter if they know the chamber of interest and the diagnosis. The new mapping system has been in use at this facility for 3 months at the time of this writing and we have completed 77 procedures. Initially, during the learning curve, there was an increase in our time per case, and an increase in the cost per case due to the extra catheter. We feel this technology has enabled us to finally resolve some very difficult arrhythmias, thereby avoiding return trips to the lab for this special subset of patients. During this training period, we learned that it is important to keep patient privacy and confidentiality controlled. There are many people in the room during these procedures. We spent extra time prior to the procedure to obtain permission from the patient and reassure them this was normal. Labs planning to invest in this technology must also take into consideration the potential increase in volume. As mentioned above, we are treating people who were for the most part considered untreatable. This has increased our volumes by an average of 10-15 cases per month and has increased our hours of operation from the usual 8-12 and 14-hour days. Recently, the Seton Medical Center was honored by the visit of the inventor of this system: Graydon E. Beatty. Mr. Beatty is the founder and Chief Technical Officer of ESI. The major advantage we hope to realize is a decrease in the amount of time it takes to efficiently identify and target the exact arrhythmia sites, thereby improving the ability to treat patients. Although there is no current additional reimbursement for this new technology we are hoping to see a specific reimbursement for the use of non-contact mapping in the future. Seton Heart Center EP Lab serves the Central Texas region as a tertiary care center for a 40+ county region and receives referral patients from across the state. Seton Heart Center is a member of the Seton Healthcare Network, a not-for-profit organization providing a full range of healthcare services at 22 locations in Central Texas. Seton is the fourth largest employer in Central Texas. For information about Seton Heart Center, visit our website at: www.seton.net/RacingHearts Texas Cardiac Arrhythmia, PA (TCA) based in Austin, provides cardiac EP throughout the state of Texas. Drs. Rodney P. Horton, MD, Robert C. Canby, MD, Jason D. Zagrodzky, MD, G Joseph Gallinghouse, MD, and Sam J. Barbera, MD are dedicated to the detection and treatment of heart rhythm disturbances. In conjunction with Texas Cardiac Arrhythmia Research Foundation, TCA contributes to a body of knowledge within the field of EP, and provides patients with cutting edge technology. For information visit our website at: www.austinheartbeat.com For more information about the ESI system, contact Endocardial Solutions at 1-800-374-8038, ext. 7911, or visit: www.endocardial.com. The following cases demonstrate the ability of this new mapping technology.

Case Report #1. S.L. is a 55-year-old male with a history of ischemic heart disease and an implantable cardioverter-defibrillator (ICD) implant. He received an occasional effective shock for a fast and unstable ventricular tachycardia (VT). In addition to this, he received up to 30 therapies a day (mostly anti-tachycardia pacing) for a slower VT. He was brought to the EP lab on March 24, 2001 to map and ablate this VT. With pacing protocols, the clinical VT was induced. Conventional mapping was performed with a pacing catheter in the right ventricle and a four-pole catheter in the left ventricle (LV) per a retrograde approach. This confirmed what the surface 12L EKG suggested, which was a LV tachycardia. The EnSite ® catheter was positioned in the retrograde approach with a 9 Fr introducer in the left femoral artery (LFA). The balloon was positioned in the apical region and the guidewire was removed. The tachycardia was induced, recorded on the system, and then terminated. The small segment was mapped and an early activation site, path and exit were on the 3D map. This was an area posterior-lateral, near the apex. The tachycardia was again induced and terminated to confirm the site. The ablation strategy was to dissect a line through the path and place a few lesions along the path. The area that produced the most amount of ectopy and termination of ectopy during the application of radiofrequency (RF) energy was the area at which the activation slowed. After the strategy of lesions was complete, the targeted tachycardia could no longer be induced. The only tachycardia induced at this time was the faster VT.

Case Report #2. C.H. is a 53-year-old male with prior flutter ablation, which was unsuccessful at that time. He was taken to the EP lab to map and navigate to the critical circuit. An 8 Fr introducer was placed in the right femoral vein (RFV) for the ablation catheter and a 9 Fr introducer in the RFV for the EnSite catheter. Geometry was created in five minutes, defining the anatomic boundaries of the right atrium. As a note, the coronary sinus ostium was very large, with the upper boundary of the Os being closer to the His than typical anatomy. After geometry was obtained, a short segment of the tachycardia was recorded. The patient presented to the lab in atrial flutter, so induction of the tachycardia was not necessary. This atrial flutter was mapped and circuit demonstrating counterclockwise propagation around the tricuspid valve using the isthmus a typical atrial flutter. While watching the wavefront of propagation, a critical narrowed isthmus of conduction was noted and labeled. Using the EnGuide signal, the Dr. Horton navigated the tip of the ablation catheter to the labeled area for RF application. Five seconds into the first burn, the tachycardia broke and the rhythm converted to regular sinus rhythm. A second lesion was applied to finish the burn. Lateral and medial pacing were performed to observe for bi-directional block. After a total of 40 minutes, the EnSite catheter was removed.

Case Report #3. T.F. is a 41-year-old female with a fifteen-year history of episodic aberrantly conducting atrial tachycardia. This study was performed on April 4, 2001, and was the fifth EnSite procedure at Seton Medical Center. A conventional EP study was performed to determine inducibility of the tachycardia utilizing His and HRA catheters. The EnSite catheter was then placed in the mid Right Atrium over a 0.032´´ guidewire. Geometry was created in five minutes to determine the anatomical boundaries of the chamber. Using pacing protocols, the tachycardia was induced and mapped to a site on the lateral wall of the right atrium, in the mid crista terminalis area. RF lesions were placed at the sites labeled as early activation for these PACs. After ablation, the tachycardia could no longer be induced.

Case Report #4. C.M. is a 54-year-old male with a history of episodic atrial fibrillation. An 8 Fr trans-septal sheath positioned in the left atrium for the ablation catheter. A second 8 Fr trans-septal sheath was positioned in the left atrium for a 0.032´´ guidewire. This guidewire was positioned in the left upper pulmonary vein. With the guidewire in position, the 8 Fr trans-septal sheath was removed and exchanged for a short 9 Fr sheath for the EnSite catheter. The EnSite was positioned in the mid-chamber position.