Magnetically induced currents in the canine heart: a finite element study

Area of Science:

• Biophysics
• Computational Biology
• Medical Imaging

Background:

• Time-varying magnetic fields can induce currents in biological tissues.
• Irregular heart rhythms in canines have been linked to exposure to specific magnetic field configurations.
• Accurate modeling of thoracic conductivity is crucial for understanding bioelectromagnetic interactions.

Purpose of the Study:

• To develop and utilize a detailed 3D finite element model of a canine thorax to simulate induced electromagnetic fields and currents.
• To estimate the stimulation threshold of the canine heart when exposed to a time-varying magnetic field from a figure-eight coil.
• To assess the sensitivity of induced myocardial fields to variations in thoracic model geometry and conductivity.

Main Methods:

• A 3D finite element model of a canine thorax was constructed using CT scan data.
• The model incorporated seven isotropic tissue conductivities and anisotropic skeletal muscle conductivity.
• Simulations were performed to calculate induced fields and currents, and sensitivity analyses were conducted on model parameters.

Main Results:

• Myocardial fields showed mild sensitivity to thoracic model size.
• Thoracic model shape, conductive inhomogeneity, and anisotropy significantly impacted the magnitude and distribution of induced myocardial fields and currents.
• An induced peak field magnitude of approximately 1 V/cm was estimated as the threshold for cardiac stimulation.

Conclusions:

• Thoracic geometry and conductivity properties are critical factors in determining the effects of time-varying magnetic fields on the heart.
• The developed 3D finite element model provides valuable insights into the bioelectromagnetic effects of magnetic fields on cardiac tissue.
• A threshold of approximately 1 V/cm is suggested for magnetic field-induced cardiac stimulation in canines under the simulated conditions.