PACING THRESHOLDS OF TEMPORARY EPICARDIAL ELECTRODES - VARIATION WITHELECTRODE TYPE, TIME, AND EPICARDIAL POSITION

We compared the variation in pacing thresholds of two widely used temp orary pacing electrodes at different epicardial sites in 67 patients a fter coronary artery operations performed with either cardioplegia or ventricular fibrillation. In 33 patients, a bare, braided pacing wire (DW) was placed on the right ventricle and a Medtronic localized epica rdial electrode (MED), on each ventricle. In the other 34 patients, th e DW wire was placed on the right atrium and a MED electrode, on each atrium. Pacing thresholds were measured at the time of placement; at 1 hour, 6 hours, and 12 hours postoperatively; and daily for 4 days. Th e pacing thresholds (mean +/- standard error of the mean) at implantat ion were as follows: DW wire = 0.93 +/- 0.08 V and MED electrode = 0.6 3 +/- 0.09 V in the atria. On the fourth postoperative day, the pacing thresholds were DW = 2.08 +/- 0.21 V and MED = 1.19 +/- 0.22 V in the ventricles and DW = 2.33 +/- 0.29 V and MED = 1.04 +/- 0.09 V in the atria. The pacing thresholds of both types of wire increased significa ntly over time, but this deterioration was more pronounced with the br aided wire both on the ventricle and on the atrium. The pacing thresho ld patterns were not affected by chamber side or mode of myocardial pr eservation. The braided ventricular wire failed to capture after 24 ho urs in 9 of 30 patients, whereas the localized epicardial electrode ca ptured in all instances (p < 0.001). There was no significant differen ce in failure rate between the two wires in the atrial position. Local ized epicardial electrodes have consistently lower pacing thresholds t han braided wires in both the ventricles and the atria and are less pr one to failure in the ventricular position.