Variation in pacing impedance: impact of implant site and measurement method.
BACKGROUND
Variations in pacing impedance may be observed during implantation of various active fixation pacing leads. However, these variations can be influenced by the nature of the fixation, the implant site, or the measurement method. Here we describe implant dynamics for a 4.1F, catheter-delivered pacemaker lead.


METHODS
Endocardial active fixation leads were implanted under direct intracardiac visualization in two right atrial sites and three right ventricular sites in isolated swine (n = 6) and human (n = 4) hearts. Impedance measurements were recorded at each site employing three different measurement techniques-Pacing System Analyzer (PSA) 5311, PSA 2090, and the Impedance Tone Box (Medtronic, Inc., Minneapolis, MN, USA)-with four different degrees of lead fixation: helix touching, one turn fixed (1 TF), two turns fixed (2 TF), and overtorqued.


RESULTS
Pacing impedances increased from touching to 1 TF to 2 TF at all implant sites in both swine and human hearts. Overtorquing applied to leads was associated with visible distortion at the endocardial tissue-lead interface in at least 60% of swine (18 of 30 implants) and human hearts (nine of 14 implants). Impedance values in the right atrial high septum were significantly larger than in any other implant site (P < 0.05). The three measurement methods did not yield significantly different impedance measurements.


CONCLUSIONS
Variations in measured impedances were associated with the nature of implant fixation at all sites in both swine and human hearts.
Anderson
Sara E
SE
Department of Biomedical Engineering , University of Minnesota, Minneapolis, MN 55455, USA.
Skadsberg
Nicholas D
ND
Laske
Timothy G
TG
Benditt
David G
DG
Iaizzo
Paul A
PA
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017097:Electric Impedance; D004567:Electrodes, Implanted; D006329:Heart Conduction System / Q000502:physiology*; D010138:Pacemaker, Artificial; D019919:Prosthesis Implantation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine