[Effects of electrocautery on the threshold values of permanent pacing. An experimental study]

One of the hazards of high frequency electrical interference (electrocautery) with cardiac pacing is thought to be related to an increase in the threshold values leading to loss of pacing. This hypothesis was examined in an experimental study performed on 5 dogs. A pacing catheter was introduced via the right jugular vein and positioned at the apex of the right ventricle and connected successively to several stimulators implanted in a latero-cervical subcutaneous pocket. A Bovie 400 CT generator was used to deliver a high frequency 1.75 MHz current between a probe applied near to the pacemaker pocket and an electrode placed under the right leg. One or two 5 second bursts were applied for each make of pacemaker, making a total of 3 to 6 applications per animal. A detecting circuit enabled the measurement of the currents in the catheter during the application. The thresholds of pacing were measured before and after each manipulation for several pacing impulse durations. At the maximal output of the generator, the highest recorded current was 117 mA (modulated) and 141 mA (unmodulated). The thresholds of stimulation did not change significantly and the pacing catheter impedance was also stable. This study suggests that high frequency current does not modify the threshold of stimulation in cardiac pacemaker patients. The loss of pacing sometimes observed after the use of electrocautery is probably related to pacemaker dysfunction.