Experimental Study of the Magnetohydrodynamic (MHD) Effect with respect to Intracardiac ECG Signals W. B. Buchenberg 1, G. Hoppe 1, R. Lorenz 1, W. Mader 2, P. Laudy 3, C. Bienek 4 and B. Jung 1 1 Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany, 2 Freiburg Center for Data Analysis and Modeling, Albert-Ludwigs-University, Freiburg, Germany, 3 CardioTek B.V., Maastricht-Airport, Netherlands, 4 R&D, Schwarzer GmbH, Heilbronn, Germany

ELECTROPHYSIOLOGIC (EP) STUDIES assess cardiac electrical system diagnosis and therapy of EP disorders catheter guidance:  X-ray fluoroscopic imaging disadvantages:  x-ray exposure (staff + patient)  poor tissue contrast  alternative imaging modalities: Magnetic Resonance Imaging (MRI) 1 SERVIER Medical Art catheters 1

MAGNETOHYDRODYNAMIC (MHD) EFFECT 1 Tenforde et al. Bioelectromagnetics 1983;4:1-9 2 Tenforde Biophysics & Molecular Biology 2005;151: Gupta et al. IEEE 2008; 55(7): Tse et al. ISMRM2012 talk #206 distortion of surface ECGs 1,2,3 and intracardiac ECGs (iEGMs) 4 B = 0 TB ≈ 1.5 T s u r f a c e E C G s

MAGNETOHYDRODYNAMIC (MHD) EFFECT 1 Gupta et al. IEEE 2008; 55(7): Kolin A. Review of Scientific Instruments 1945;16(6): SERVIER Medical Art 3 0

establish experimental setup for simulating MHD signal with common clinical EP-devices  characterization of measured MHD-signal U meas (bipolar):  magnetic field strength  electrode distance  filter settings of recording modality  comparison of U meas with U MRI,calc from MR flow measurements  implementation of methods to remove MHD signals from intracardiac ECG signal (iEGMs) OBJECTIVES

EXPERIMENTAL SETUP simulate electrical conductivity of blood: dist. H 2 O + NaCl 1.5 Tesla 50 bpm

EXPERIMENTAL SETUP simulate electrical conductivity of blood: dist. H 2 O + NaCl VAD (Ventricular Assist Device): 1.5 Tesla 50 bpm

EXPERIMENTAL SETUP simulate electrical conductivity of blood: dist. H 2 O + NaCl catheter positioning: (1) 1.5 Tesla 50 bpm U MHD

EXPERIMENTAL SETUP simulate electrical conductivity of blood: dist. H 2 O + NaCl (1) 1.5 Tesla 50 bpm

EXPERIMENTAL SETUP simulate electrical conductivity of blood: dist. H 2 O + NaCl (1) 1.5 Tesla 50 bpm

MRI FLOW MEASUREMENTS 2D slice imaging parameters TE / TR [ ms ]4.9 / 7.2 temp. res. [ ms ]7.2 voxel size [ mm³ ] 0.9 x 0.9 x 6.0 VENC IN / THROUGH- PLANE [ m/s ] 0.15 / 0.55

RESULTS – MHD SIGNAL vs. TIME U MHD,PP 1/102/93/84/75/ ± ± ± ± ± 0.12

RESULTS – MHD SIGNAL vs. TIME U MHD,PP 1/102/93/84/75/ ± ± ± ± ± 0.12 U MRI,calc [mV]8.67 ± ± ± ± ± 0.18

RESULTS – MHD VOLTAGE vs. DISTANCE 24.3 ± 1.0 MRI~ 25.3

RESULTS – MHD VOLTAGE vs. MAGNETIC FIELD 1/102/93/84/75/ ± ± ± ± ± 1.0 MRI~ 25.3

RESULTS – MHD VOLTAGES (2/9)

RESULTS – MHD VOLTAGES high pass filtered (f cut off = 0.05 Hz) (2/9)

RESULTS – HIGH PASS FILTERS U MHD,PP (f cut off : 0.2 Hz) ≈ U MHD,PP (f cut off : 0.05 Hz) (within ± 4%) U MHD,PP (f cut off : 40 Hz) remaining U MHD,PP ≤ 3% U MHD,PP (f cut off : 80 Hz) remaining U MHD,PP ≤ 2%

DISCUSSION & OUTLOOK experimental setup established successfully MHD potential (bipolar measured) was characterized: shows linear dependency on B 0, d follows characteristics of velocity pattern same order of magnitude as intracardiac signals 1 MR flow data - post processing: MHD signal reconstructed using MR velocity data measured and calculated MHD signal agree very well Outlook iEGM data correction based on MR flow measurements 1 Cassidy et al. Circulation 1984;70(1):37-42.

THANK YOU FOR YOUR ATTENTION! ACKNOWLEDGEMENTS : Christoph Benk Mr. Knieriem, St. Jude Medical Mr. Simon, Mr. Baecke, seleon gmbh Grant support by EUROSTARS Program Grant #01QE1004D