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Voltage-based electroanatomic mapping system for MR-guided cardiac electrophysiology: preliminary swine validations
Journal of Cardiovascular Magnetic Resonance volume 15, Article number: O88 (2013)
MRI produces images that serve as luminal, edema, & scar maps to assist in the Electrophysiological (EP) treatment of ventricular and atrial arrhythmias . Until MR-compatible EP devices are widely available, there will be a need 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 . The study objective was to conduct a multi-catheter registration free EAM (localization & intra-cardiac Electrogram (EGM) measurement) both in & outside of the MRI.
An MR-conditional Velocity was constructed to prevent MR gradient from reducing tracking accuracy. The system utilized an electronic switching circuit, RF-filtered electrical lines, modified surface electrode patches, & MR-conditional EP catheters . Trans-septal punctures were made in 5 intubated swine under X-ray & ICE guidance. The swine were moved to a GE 1.5T MRI suite equipped with the Velocity. Prior to the procedure, 3D ECG-gated MR Angiography (MRA) provided navigational roadmaps. Three voltage-tracked EP catheters, with 4 tracked electrodes each, were navigated simultaneously inside the MRI to acquire EAM of the heart's left & right sides, with a coronary sinus catheter providing a physiological reference (Fig1). Imaging & voltage tracking were tested simultaneously (Fig2a). To measure Velocity's catheter tracking accuracy during MR imaging, catheters were navigated to specific anatomic regions, & the change in location was observed during imaging over 10-sec increments.
EAM & catheter navigation of the swine models were performed both in & outside the MRI at >20 frames-per-second without re-registration (Fig1). Imaging was conducted simultaneously with tracking (Fig2a), & catheter position remained stable during the entire imaging session (Fig1a). The median catheter electrode locations changed by 0.33-0.37 mm, while the standard deviation (SD) of the locations increased by only 0.23-0.45 mm (Fig2b). Since some of the positional SD was due to respiratory or cardiac motion, this slight increase in positional oscillation was hard to visually detect in EAM. Concurrent imaging & tracking were successful during sequences with TR>32 ms, capturing cardiac tissue during critical procedural stages. Image quality reduction of <5% was shown in FSE & GRE sequences. High-fidelity Intra-cardiac EGMs were obtained even during imaging (Fig2c). Electrode heating was <1oC under sequences of 4 Watt/kg.
MRI-conditional voltage tracking allows simultaneous catheter tracking & MR imaging, permitting registration-free EAM in& outside MRI during EP procedures.
NIH U41-RR019703, R43 HL110427-01, AHA 10SDG261039.
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Tse, Z., Dumoulin, C., Byrd, I. et al. Voltage-based electroanatomic mapping system for MR-guided cardiac electrophysiology: preliminary swine validations. J Cardiovasc Magn Reson 15, O88 (2013) doi:10.1186/1532-429X-15-S1-O88
- Tracking Accuracy
- Image Quality Reduction
- Catheter Tracking
- Electroanatomic Mapping System
- Catheter Navigation