Volume 14 Supplement 1

Abstracts of the 15th Annual SCMR Scientific Sessions: 2012

Open Access

MRI guided electrophysiological intervention with a voltage-based electro-anatomic mapping system

  • Zion Tse1,
  • Charles Dumoulin2,
  • Ronald Watkins3,
  • Israel Byrd4,
  • Jeffrey Schweitzer4,
  • Raymond Kwong1,
  • Gregory F Michaud1 and
  • Ehud J Schmidt1
Journal of Cardiovascular Magnetic Resonance201214(Suppl 1):P206

DOI: 10.1186/1532-429X-14-S1-P206

Published: 1 February 2012

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’s norm 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.

Methods

An MR-compatible ESN (Fig.1) minimized electrode heating and IQ reduction inside the scanner room with modified ESN surface-patches, ferrites on coaxial ESN leads (Fig.1(2)) , and RF filters at the penetration panel. Outside the scanner room, an electronic switching circuit, triggered by a sequence’s gradient-ramps and radio-frequency-pulse transmission (GR&RF), disconnected the ESN leads from the ESN receiver when GR&RF was detected, preventing noise from reaching it (Fig.1(3)). 2 SJM MR-compatible deflectable EP catheters were used (Fig.1(4)) [5]. The ESN was tested at 1.5T in heart phantoms and swine models with varying GRE, SSFP & FSE imaging parameters and slice orientations.

Figure 1

Results

Fig.1(5) shows simultaneous ESN & MR tracking of the dual ESN&MR-tracked catheter in the phantom, verifying the lack of interference between the 2 methods. 3 EAM & MRI imaging experiments were performed in swine, also equipped with sensors to measure temperature at the surface ESN electrodes. Fig.1(6) shows EAM during imaging where catheter tracking of 2 catheters (reference catheter in the Coronary Sinus (CS) & mapping catheter in the Left Atrium) was performed simultaneously on the ESN , with <5% positional error of the CS catheter relative to its position outside MRI. IQ Reduction was <5% in both SE & GRE, with tracking updated during 60-80% of sequence duration. TR elongation was required in TR<4ms sequences. Electrode temperature rise was <1oC with 4 Watt/kg SAR sequences. Surface burns did not occur.

Conclusions

An MR-compatible ESN system permits registration-free, minimal-heating, EAM for EP procedure in & outside MRI, with simultaneous imaging possible.

Authors’ Affiliations

(1)
Brigham and Women's Hopsital, Harvard Medical School
(2)
University of Cincinnati College of Medicine
(3)
Standford University
(4)
St Jude Medical, Inc.

References

  1. Dukkipati : Circulation’08.
  2. Schmidt : Circulation A&E’09.
  3. Nademanee : JACC ’04.
  4. Early : Eur. Heart J ’06.
  5. Tse: ISMRM & SCMR ‘10&’11.

Copyright

© Tse et al; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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