Acute changes in the pacing threshold after lead implantation. Comparison between retractable and sweet-tip...

Although the pacing threshold of steroid-eluting active-fixation leads remains stable over the long term, it changes rapidly after screw-in. We compared the pacing threshold in the acute phase between retractable and Sweet-Tip active-fixation leads. We studied 132 patients who were implanted with active-fixation leads for new pacemaker implantation or additional leads required due to disconnected/leaking leads. Pacing threshold was measured at 4 time points: before screw-in, immediately, and 5 and 10 minutes after screw-in. If the pacing threshold was > 1.5 volts (V) at 5 minutes, we changed the pacing site so that it became ≤ 1.5 V. A total of 169 retractable leads (Medtronic: 107 leads, St. Jude Medical: 62 leads) and 33 Sweet-Tip leads (Boston: 33 leads) were implanted. Eighty-nine leads were implanted in the atrium and 113 leads in the ventricle. Seventy patients were implanted with both atrial and ventricular leads. The pacing threshold of Sweet-Tip leads increased immediately after screw-in, while that of retractable leads decreased (Sweet-Tip: 0.20 ± 0.57 V, Retractable: -0.15 ± 0.53 V, P < 0.05). The pacing threshold of both types of leads decreased similarly from immediately to 5 minutes after screw-in (Sweet Tip: -0.29 ± 0.43 V, Retractable: -0.25 ± 0.36 V, P = NS). Few changes in the threshold were detected between 5 and 10 minutes. Because the pacing threshold of Sweet-Tip active-fixation leads increased immediately after screw-in and that of both type leads decreased from immediately to 5 minutes, we should measure the pacing threshold from 5 minutes after screw-in.