Interaction between permanent cardiac pacing and electrocautery: the significance of electrode position

The danger in utilizing electrocautery during a surgical procedure on a pacemaker patient depends, to a great extent, on the position of the electrodes. We have studied this influence in an experimental model consisting of a plexiglass tank filled with a saline solution. Seven pacemakers were successively attached to an immersed and fixed frame and connected to a lead whose tip remains in the same location throughout the experiments. An ERBOTOM T 400 C generator (450 kHz) was used in an unmodulated unipolar mode at a maximum output (400 W). The high frequency current was delivered between a patch located successively at six preset positions in the tank and another electrode applied to 176 surface locations. For each position, we measured the currents in the lead with a separate measurement circuit connected in parallel on the same lead. Results were displayed on a map. Regardless of the patch position, currents were: (1) at a maximum when high frequency was delivered close to the pacemakers and around the tip of the lead; (2) negligible when applied to the path followed by the lead; and (3) a function of the distance between electrodes. These results may help to formulate recommendations to prevent accidents when using electrocautery in pacemaker patients.