Defibrillation current density imaging: comparison of in-vivo and post-mortem measurements in a pig

Current density imaging (CDI) is an MRI technique used to measure electrical current density vectors throughout a volume of tissue. Previous work used CDI to measure current pathways through the heart and chest of a post-mortem pig when current is applied using external flexible defibrillation electrodes with typical anterior-anterior positioning. In these post-mortem studies, current pathways were probably influenced by the anisotropic conductivity of the tissues. This work aims to compare post-mortem ( approximately 15 min. and approximately 1 hour after death) results with new in vivo CDI measurements. These measurements indicate that the macroscopic (i.e. across the whole body) current pathways remain similar before and after death, however, at a smaller scale (i.e. distances of a few cm) current pathways are different, particularly in the heart. This comparison demonstrates the influence on current pathways of rapidly changing electric properties of tissue following death.