EP Lab Digest - October 2007 - (Page 14)

14 EP CASE STUDY OCTOBER 2007 Use of Magnetic Catheter Navigation for Ablation of Focal Tachycardias Mintu Turakhia, MD, Albert M. Kim, MD, PhD, and Byron K. Lee, MD Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, University of California, San Francisco San Francisco, California Focal atrial and ventricular tachycardias are common diagnoses encountered in the electrophysiology laboratory. Arrhythmia burden varies from rare or paroxysmal premature beats to sustained or incessant monomorphic tachycardia. Location of the arrhythmia foci can vary, and careful contact mapping is often required to precisely locate the focus. Unfortunately, catheter ablation may fail, even when the focus is endocardial. The spatial resolution of activation mapping or pace mapping may be compromised by limitations in the steerability or reach of conventional unidirectional or bidirectional ablation catheters. The tip of a conventional steerable ablation catheter held by the operator may swing or move away from the desired ablation point with respiration and normal cardiac motion.The pressure that can be applied to ablation catheters in order to improve contact is often limited by the risk of cardiac perforation. Larger tip ablation catheters (8 mm) may be used to compensate for some of these limitations, but the accuracy of contact activation mapping and pace mapping is compromised. Magnetic robotic catheter navigation may help overcome many of the limitations of conventional catheter ablation. The Niobe® system (Stereotaxis, Inc., St. Louis, Missouri) uses an externally applied magnetic field to direct the orientation of a catheter.The magnet system consists of two contralateral focused-field permanent neodynium-iron-boron magnets in a permanent housing that are rotated into the active position on the left and right of the patient’s torso.1 In this navigational position, the magnets create a small but uniform magnetic field of 15 cm overlying the patient’s heart. The field strength is 0.08 Tesla, which is several orders of magnitude less powerful than cardiac MRI magnets (typically 1.02.0 Tesla). In our laboratory (Figure 1), the Niobe navigation system is integrated with a monoplane flat panel system (Philips Corporation). The mapping and ablation catheter is equipped with a series of small permanent magnets that allow it to be controlled in the magnetic field. 2 The catheter tip can be deflected by changing the orientation of the external magnetic field. Preset magnetic vectors based on standard cardiac anatomy can be used to direct the catheter to the desired location. In addition, custom vectors can be stored and reapplied for automatic navigation. A computer-controlled motor drive unit (Cardiodrive™) is used to remotely advance and retract the catheter. The system allows precise navigation with a spatial resolution of 1° of omni-directional deflection and 1 mm for catheter advancement and retraction. The Navigant ™ computer control system, located in the shielded control room, allows operators to control all aspects of catheter navigation, mapping, pacing, and ablation. The operator may control the catheter using any desired combination of the joystick control, keyboard, or mouse. The Stereotaxis system is integrated with the CARTO mapping system (Biosense Webster, Inc., a Johnson & Johnson company, Diamond Bar, California), and navigation can be performed directly from the electroanatomic map or preprocedure cardiac CT or MRI. We have found that use of the Stereotaxis Niobe system in combination with three-dimensional electroanatomic mapping is an efficient and effective approach for mapping and ablation of focal arrhythmias. Although much of the initial excitement for the Niobe system is based on its ability to simplify atrial fibrillation ablation, we believe that it may also have a major impact on the success of focal arrhythmia ablation. Here we present two cases to demonstrate the feasibility and utility of magnetic navigation for these types of arrhythmias. Case Report #1 A 38-year-old man presented with frequent palpitations. Ambulatory ECG monitoring revealed frequent atrial premature complex (APC) and supraventricular tachycardia. Invasive electrophysiology testing with programmed stimulation demonstrated features consistent with a focal atrial tachycardia (cycle length 410 msec), including triggered bursts of atrial tachycardia, overdrive suppression and a V-A-A-V response with ventricular overdrive pacing, and failure to initiate or terminate with extrastimuli. Activation mapping was performed using a 4 mm NaviStar® RMT catheter (Biosense Webster, Inc.). After confirming registration of the Stereotaxis vectors to the fluoroscopic system, the automated magnetic navigation feature was used to create a three-dimensional anatomic shell of the right atrium, vena cava, and tricuspid annulus. Contact Figure 1. View of the UCSF Stereotaxis lab. In the foreground is the Navigant®control system, allowing remote magnetic catheter navigation without operator fluoroscopy exposure. In the background is the laboratory, with a Stereotaxis magnet seen in the parked position. Photo courtesy of Jeffrey Olgin, MD.

Table of Contents Feed for the Digital Edition of EP Lab Digest - October 2007

Finally! The New Registered Cardiac Electrophysiology Specialist (RCES) Credential: Interview with Christopher M. Nelson, RN, RCIS, FSICP ECG 101: Closing the Gap Phenomenon Contents Letter from the Editor ICD Patient Support Group: St. Peter’s Hospital Spotlight Interview: Community Healthcare System Use of Magnetic Catheter Navigation for Ablation of Focal Tachycardias Echocardiography: The Preeminent Front Line Screening and Diagnostic Tool for Cardiovascular Imaging and Physiological Assessment First Annual EP Lab Digest Salary Survey: Last Chance! Clinical Trial Update: 2007 Email Discussion Group Adopting and Implementing the AF Ablation Consensus Statement Electrophysiology in the West Summit Events Calendar The Sustained Treatment of Paroxysmal Atrial Fibrillation (STOP AF) Clinical Trial: Interview with Kevin Wheelan, MD Industry News and Products

EP Lab Digest - October 2007

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