Optimal location for temporary epicardial pacing leads following open heart surgery.

Temporary epicardial pacing wires are routinely placed in patients undergoing cardiac surgery. Eighteen suitable patients undergoing elective surgery were prospectively studied. Their sensing and stimulating characteristics were studied at various locations. Subepicardial pacing leads were applied to the lateral wall of the LV, apex of the LV, anterior wall of the RV, diaphragmatic wall of the RV, and diaphragmatic wall of the LV. Impedance, R wave amplitude, slew rate, and stimulation thresholds were measured on postoperative days 1 and 5. Impedance remained unchanged in time with no significant differences between locations. R waves and slew rates were significantly lower in the anterior RV wall. Stimulation thresholds displayed no differences on day 1, but they increased significantly in all locations on day 5. These thresholds were significantly lower in the lateral and diaphragmatic LV walls on day 5, and the rate of voltage increase was also lower in these two locations. Five patients presented phrenic nerve stimulation when stimulating the lateral LV wall. The authors advocate the diaphragmatic wall of the LV as the best location for placing temporary leads. The anterior wall of the RV is not recommended for pacing purposes.