title: Acute changes in pacing threshold and R- or P-wave amplitude during permanent pacemaker implantation.
abstract: This study examines the changes in pacing threshold and R- or P-wave amplitude during the first 30 minutes after implantation of tined and screw-in leads. The leads examined were those of 1 manufacturer (Medtronic) and consisted of 3 ventricular pacing leads (model numbers 6957 unipolar screw-in [11 patients], 6961 unipolar tined [12 patients] and 6962 bipolar tined [7 patients]) and 1 atrial lead (model number 6957J unipolar screw-in [10 patients]). After optimal lead position was obtained fluoroscopically in the right ventricular apex or right atrium, the pacing threshold and R- or P-wave amplitudes were measured at 5-minute intervals for 30 minutes. The acute ventricular pacing threshold with the screw-in lead was significantly higher than with the tined lead (0.84 +/- 0.17 vs 0.58 +/- 0.15 volts; p less than 0.001). There was a significant (p less than 0.001) acute decrease in the ventricular pacing threshold with both lead types, with the maximum decrease occurring 5 minutes after lead implantation. There was a significant acute increase in R-wave size with the ventricular screw-in lead that peaked 20 minutes after lead implantation (11.9 +/- 3.0 to 14.7 +/- 4.1 mV; p less than 0.001). The atrial screw-in lead behaved in a manner identical to its counterpart in the ventricle. In conclusion, there are acute changes in the pacing threshold and R- or P-wave amplitude obtained with tined and screw-in pacing leads.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0022.
authors.forename: M
authors.initials: M
authors.lastname: de Buitleir
authors.forename: W H
authors.initials: WH
authors.lastname: Kou
authors.forename: S
authors.initials: S
authors.lastname: Schmaltz
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000368:Aged; D004567:Electrodes, Implanted; D004867:Equipment Design; D005260:Female; D006327:Heart Block / Q000628:therapy; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D012804:Sick Sinus Syndrome / Q000628:therapy; D013997:Time Factors