Published Online
on October 19, 2009

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Original Article

Electro–Anatomic Mapping and Radio–Frequency Ablation of Porcine Left Atria and Atrio-Ventricular Nodes using Magnetic Resonance Catheter Tracking

Ehud J. Schmidt^1,8; Richard P. Mallozzi²; Aravinda Thiagalingam³; Godtfred Holmvang³; Andre d'Avila⁴; Renee Guhde²; Robert R. Darrow²; Glenn Slavin⁵; Maggie Fung⁵; Jeremy Dando⁶; Lori Foley³; Charles L. Dumoulin⁷ and Vivek Y. Reddy⁴

¹ Brigham and Women's Hospital & Massachusetts General Hospital, Boston, MA;
² GE Global Research, Niskayuna, NY;
³ Massachusetts General Hospital, Boston, MA;
⁴ University of Miami, Miami, FL;
⁵ GE Healthcare Applied Science Laboratory, Bethesda, MD;
⁶ St. Jude Medical, Minnetonka, MN;
⁷ Cincinnati Children's Hospital Medical Center, Cincinnati, OH

^* Corresponding author; email: eschmidt3{at}partners.org

Background—The MRI-compatible Electro-Physiology system previously utilized for MR-guided left-ventricular Electro-Anatomic Mapping (EAM) was enhanced with improved MR-Tracking, an MR-compatible RF ablation (RFA) system and higher-resolution imaging sequences to enable mapping, ablation, and ablation monitoring in smaller cardiac structures. MR-tracked navigation was performed to the Left Atrium (LA) and Atrio-Ventricular (AV) node, followed by LA EAM, and RFA of the Pulmonary Veins (PVs) and AV node.

Methods and Results—1 ventricular ablation, 7 PV ablations, 3 LA mappings and 3 AV node ablations were conducted. Three MRI-compatible devices (ablation/mapping catheter, torquable sheath, stimulation/pacing catheter) were used, each with 4-5 tracking-micro-coils. Trans-septal puncture was performed under X-ray, with all other procedural steps performed in the MRI. Pre-acquired MR image roadmaps served for real-time catheter navigation. Simultaneous tracking of three devices was performed at 13 frames per second. LA mapping and PV RFA were performed using tracked ablation catheters and sheaths. Ablation points were registered and verified post-ablation using 3D Myocardial Delayed Enhancement (3D-MDE), and post-mortem gross tissue examination. Complete LA EAM was achieved in 3/3 pigs, Right Inferior PV (RIPV) circumferential ablation in 3/7 pigs, with incomplete isolation caused by limited catheter deflection. During AV node ablation, ventricular pacing was performed, 3 devices were simultaneously tracked, and intra-cardiac ECGs displayed. 3D-MDE visualized node injury 2 min post-ablation. AV node block succeeded in 2/3 pigs, with 1 temporary block.

Conclusions—LA mapping, PV RF ablation, and AV node ablation, were demonstrated under MRI-guidance. Intra-procedural 3D-MDE assessed lesion positional accuracy and dimensions.

Key Words: ablation • electrophysiology • magnetic resonance imaging • mapping