title: Rapid decline in acute stimulation thresholds with steroid-eluting active-fixation pacing leads.
abstract: OBJECTIVE
  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 45/94 (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, 43/45 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%) leads falling 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.
authors.affiliation: Department of Cardiology, The Royal Melbourne Hospital, Victoria 3050, Australia.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kistler
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
authors.forename: Simon P
authors.initials: SP
authors.lastname: Fynn
authors.forename: Suresh
authors.initials: S
authors.lastname: Singarayar
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Roberts-Thomson
authors.forename: Catherine B
authors.initials: CB
authors.lastname: Lindsay
authors.forename: Uyen
authors.initials: U
authors.lastname: Khong
authors.forename: Paul B
authors.initials: PB
authors.lastname: Sparks
authors.forename: Neil
authors.initials: N
authors.lastname: Strathmore
authors.forename: Harry G
authors.initials: HG
authors.lastname: Mond
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004343:Drug Implants; D004567:Electrodes, Implanted; D004867:Equipment Design; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011446:Prospective Studies
chemical_list: D004343:Drug Implants; D005938:Glucocorticoids