title: Current of injury predicts adequate active lead fixation in permanent pacemaker/defibrillation leads.
abstract: OBJECTIVE
  The aim of this study was to determine whether current of injury can guide adequate placement of active-fixation pacing leads.
  
  
  BACKGROUND
  Active-fixation leads cause injury to the myocardium at the time of fixation, manifested as a current of injury (COI) that may result in acute elevation of pacing thresholds. The relationship of COI to subsequent improvement in pacing thresholds is not clear.
  
  
  METHODS
  Sixty-five patients undergoing active-fixation lead implantation were enrolled. Current of injury was characterized as the duration of the intracardiac electrogram (EGM) and the magnitude of ST-segment elevation. Pacing parameters were measured up to 10 min after fixation.
  
  
  RESULTS
  A total of 96 active-fixation leads were studied, and 76 leads had a current of injury. From baseline to the time of fixation, the duration of the intracardiac EGM in ventricular leads increased from 150 +/- 31 ms to 200 +/- 25 ms (p < 0.001), and the ST-segment increased from 1.5 +/- 0.2 mV to 10.0 +/- 2.0 mV (p < 0.001), with subsequent improvement in pacing thresholds from 1.5 +/- 0.4 V to 0.8 +/- 0.3 V (p < 0.001) at 10 min. Atrial leads with a current of injury had similar findings. Of the 20 leads without a COI, 5 dislodged acutely and 15 had high pacing thresholds at 10 min, requiring repositioning.
  
  
  CONCLUSIONS
  The development of a COI indicates that within 10 min of fixation, pacing threshold will return to an acceptable range even if the initial measurement is high. Conversely, without a COI, lead fixation is not adequate and the lead should be repositioned.
authors.affiliation: Department of Medicine, Division of Cardiovascular Medicine, University of Florida College of Medicine, Gainesville, FL 32610-0277, USA. saxonsj@medicine.ufl.edu
authors.forename: Sherry J
authors.initials: SJ
authors.lastname: Saxonhouse
authors.forename: Jamie B
authors.initials: JB
authors.lastname: Conti
authors.forename: Anne B
authors.initials: AB
authors.lastname: Curtis
mesh_terms: D000368:Aged; D020517:Atrial Appendage / Q000293:injuries / Q000503:physiopathology* / Q000601:surgery*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D004567:Electrodes, Implanted; D005260:Female; D006335:Heart Injuries / Q000209:etiology / Q000503:physiopathology*; D006352:Heart Ventricles / Q000293:injuries / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011237:Predictive Value of Tests; D013997:Time Factors