Measurement of cardiac magnetostimulation thresholds in pigs
Valerie Klein1,2, Jaume Coll-Font2,3,4, Livia Vendramini2, Donald Straney2, Mathias Davids1,2,3, Natalie G. Ferris2,5, Lothar R. Schad1, David E. Sosnovik2,3,4,5, Christopher Nguyen2,3,4, Lawrence L. Wald2,3,5, and Bastien Guérin2,3
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany, Mannheim, Germany, 2Department of Radiology, Massachusetts General Hospital, A. A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 3Harvard Medical School, Boston, MA, United States, 4Cardiovascular Research Center, Cardiology Division, Massachusetts General Hospital, Charlestown, MA, United States, 5Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States
We measured cardiac magnetostimulation thresholds in ten healthy pigs by discharging a 220-µF capacitor into a flat spiral coil placed close to the pigs’ torso. We used MR Dixon images to locate the porcine heart and determine the relative coil position to calculate the B-field in the heart (Biot-Savart). The average threshold for cardiac magnetostimulation during diastole was dB/dt≈1570±320 T/s at the center of the heart. This value is >10X greater than the IEC 60601-2-33 cardiac dB/dt limit for the effective stimulus duration of the magnetic stimulator system used in the experiments (0.45 ms).
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