Jeffrey A. Schweitzer

Voltage-based device tracking in a 1.5 tesla MRI during imaging: initial validation in swine models

Voltage‐based device‐tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological cardiac‐arrhythmia therapy. During electrophysiological procedures, electro‐anatomic mapping workstations provide guidance by integrating VDT location and intracardiac electrocardiogram information with X‐ray, computerized tomography, ultrasound, and MR images. MR assists navigation, mapping, and radiofrequency ablation. Multimodality interventions require multiple patient transfers between an MRI and the X‐ray/ultrasound electrophysiological suite, increasing the likelihood of patient‐motion and image misregistration. An MRI‐compatible VDT system may increase efficiency, as there is currently no single method to track devices both inside and outside the MRI scanner.

MRI Guided Electrophysiological Intervention with a Voltage- Based Electro-Anatomic Mapping System

Background MRI visualizes luminal & vessel-wall anatomy, and identifies edema & scar tissue, contributing to improved electrophysiological (EP) ablative procedures for treatment of Ventricular Tachycardia & Atrial Fibrillation. MRI-guided EP interventions will be performed for the foreseeable future partially in & outside MRI, due to the need for X-ray/Ultrasound-compliant devices. Electromagnetically tracked catheter procedures, today’ sn orm for most EP procedure phases; vascular navigation, Electro-Anatomic-Mapping (EAM, the diagnostic and therapeutic phases), can only be performed outside MRI. Separate MRI tracking is required in MRI, complicating EP procedures which require moving in & out of the bore [1,2]. Continuous catheter tracking using a single system would allow registration-free EAM in & outside MRI. The goal was developing an MR-compatible St. Jude Medical (SJM) EnSite NavX (ESN) voltage-based tracking [3]. ESN applies 5.8/8.0 kHz voltage bursts between 3 pairs of electrodes on the chest, detecting a catheter’s position [4], so a challenge for intra-MRI use is MR gradient ramps which interfere with ESN operation. Minimal MR Image Quality (IQ) reduction also needs to be insured, as well as <2oC patient-skin heating due to components in MRI.

Voltage-based electroanatomic mapping system for MR-guided cardiac electrophysiology: preliminary swine validations

Background MRI produces images that serve as luminal, edema, & scar maps to assist in the Electrophysiological (EP) treatment of ventricular and atrial arrhythmias [1]. Until MR-compatible EP devices are widely available, there will be an eed to perform EP partially in the MRI for imaging, and partially outside the MRI for ablation, puncture & navigation. An MR-conditional voltage-based Electroanatomic Mapping (EAM) system would allow MR-guided EP in MRI & registration-free EP to be performed outside the MRI during X-ray, Intra-Cardiac-Echo (ICE) or EAM guidance. Previously a 1.5T MR-conditional St. Jude Medical EnSite Velocity (Velocity) voltage-based EAM system was presented [2]. The study objective was to conduct a multicatheter registration free EAM (localization & intracardiac Electrogram (EGM) measurement) both in & outside of the MRI. Methods

Human & swine studies of concurrent 12-lead ECG & MRI

Background 12-lead Electrocardiogram (ECG) is a clinical standard for patient physiological monitoring. An MRI-conditional 12-lead ECG should permit detection of acute myocardial ischemia during MR imaging or MRI-guided therapy, which may improve the handling of patients with ischemic histories. MRI visualization of ischemic episodes can also enhance the understanding of ischemic progression. Previously an MR-conditional 12-lead ECG system was presented. The system was equipped with GradientRampR (2) detect S-wave to T-wave (ST) ECG elevation & perform MR imaging of a Left Anterior Descending (LAD) balloon occlusion from the onset of ischemia to death in a swine model.

MRI-compatible voltage-based electroanatomic mapping system for 3T MR-guided cardiac electrophysiology: swine validations

Background MRI provides luminal, edema, & scar images which assist in the Electrophysiological (EP) treatment of ventricular and atrial arrhythmias]. Until a complete set of MR-compatible EP-devices is available, patients must be repeatedly moved between the MRI, where imaging and mapping occur, to the conventional EP suite, where puncture, navigation and Radio-Frequency Ablation occur. MRI-conditional voltage-based electroanatomic mapping (EAM) would permit efficient MRI-guided EP, with registration-free continuation outside MRI, utilizing X-ray, Intra-Cardiac-Echo (ICE) and EAM guidance. A 1.5T EnSiteTM VelocityTM cardiac mapping system, a voltage-based EAM available from St. Jude Medical was previously validated [1,2]. Multiple-catheter EAM (localization and intra-cardiac electrocardiogram (EGM) measurement) inside a 3T MRI requires modifications.