Recordings of Impedance and Communication Between Defibrillator and Pacemaker Electrodes

External defibrillation involves short electric shocks of several thousand volts applied to the chest of patients suffering from heart stop. The shock coordinates disorganized muscle fibers of the heart which then can resume normal activity. Implanted pacemakers monitor the natural electrical activity of the heart via electrodes mounted permanently on the inside of the heart. If this activity is insufficient, the pacemaker stimulates the heart muscle by applying a short electrical impulse of a few volts. During the period of defibrillation, voltage differences arise simultaneously between various locations of the body preventing recordings of the heart's natural activity. In order to quantify parameters determining voltage and current in a conductive medium or in a myocardium when defibrillator and pacemaker electrodes are present simultaneously, impedances between electrodes positioned on conductive materials were recorded in laboratory set ups, and the methods were tested using a porcine heart in vitro.