Pacemaker interference by magnetic fields at power line frequencies

• Published in: IEEE transactions on biomedical engineering 2002-03, Vol.49 (3), p.254-262
• Main Authors: Dawson, T.W., Caputa, K., Stuchly, M.A., Shepard, R.B., Kavet, R., Sastre, A.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biological system modeling; Cardiac dysrhythmias; Cardiology. Vascular system; Conductors; Diseases of the cardiovascular system; Electric field effects; Electrodes; Electromagnetic Fields - adverse effects; Electromagnetic interference; Finite difference method; Frequency; Frequency domain analysis; Heart; Humans; Implants (surgical); Lead; Magnetic field effects; Magnetic fields; Medical sciences; Models, Cardiovascular; Numerical models; Pacemaker, Artificial; Pacemakers; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/10.983460

Human exposure to external 50/60-Hz electric and magnetic fields induces electric fields within the body. These induced fields can cause interference with implanted pacemakers. In the case of exposure to magnetic fields, the pacemaker leads are subject to induced electromotive forces, with current return paths being provided by the conducting body tissues. Modern computing resources used in conjunction with millimeter-scale human body conductivity models make numerical modeling a viable technique for examining any such interference. In this paper, an existing well-verified scalar-potential finite-difference frequency-domain code is modified to handle thin conducting wires embedded in the body. The effects of each wire can be included numerically by a simple modification to the existing code. Results are computed for two pacemaker lead insertion paths, terminating at either atrial or ventricular electrodes in the heart. Computations are performed for three orthogonal 60-Hz magnetic field orientations. Comparison with simplified estimates from Faraday's law applied directly to extracorporeal loops representing unipolar leads underscores problems associated with this simplified approach. Numerically estimated electromagnetic interference (EMI) levels under the worst case scenarios are about 40 /spl mu/T for atrial electrodes, and 140 /spl mu/T for ventricular electrodes. These methods could also be applied to studying EMI with other implanted devices such as cardiac defibrillators.