Rapid decline in acute stimulation thresholds with steroid-eluting active-fixation pacing leads

Rapid Decline in Acute Stimulation Thresholds with Steroid-Eluting Active-Fixation Pacing Leads. Background and Aim: There is an increasing use of active-fixation leads for cardiac pacing, yet concerns remain regarding initial high stimulation thresholds. The aim was to perform a detailed analysis of pacing parameters at the time of implantation to determine when lead repositioning should be considered. Methods: We performed a prospective observational study of consecutive new pacemaker implants. Detailed analysis of pacing parameters was collected at 2-minute intervals for 10 minutes, and at day 1 and week 8 following implant. Results: Ninety-four patients underwent implantation of 79 dual-chamber and 15 single-chamber pacemakers using active-fixation leads in both chambers. An initial threshold of > 1 V was demonstrated in 45194 (48%) ventricular leads (mean threshold 1.5 +/- 0.3 V). This declined rapidly to 0.9 +/- 0.3 V at 4 minutes (P < 0.01), 0.7 +/- 0.3 V at 10 minutes (P < 0.01), and 0.6 +/- 0.3 V at day 1 (P < 0.01). At day 1, 43145 leads were < 1 V There were 79 atrial leads. An initial threshold of > 1 V (mean 1.7 +/- 0.6 V) was demonstrated in 41/79 (52%) leadsfalling significantly to 1.1 +/- 0.5 V at 4 minutes (P < 0.01), 0.9 +/- 0.4 V at 10 minutes (P < 0.01), and 0.6 +/- 0.2 V at day 1 (P < 0.01). At 10 minutes, 32 of 41 leads demonstrated a threshold of < 1 V with all leads < 1 V at day 1. Thresholds were maintained medium term. Conclusions: Active-fixation leads are commonly associated with initially high thresholds that fall rapidly. An initial threshold of 2 V should be provisionally accepted and retested at 4 minutes. The majority will have a threshold of < 1 V the following day. A failure of a high threshold to decline at 4 minutes requires lead repositioning.