High atrial pacing impedance: efficient or wasteful? A comparison of an active and a passive fixation lead

We compared the stimulation characteristics of two atrial fixation leads: the CPI model 4269 (n = 45) and Cordis-Telectronics model 327-752 (n = 42). The CPI lead uses an active fixation method, whereas the Cordis-Telectronics lead is fixated passively. Impedance and threshold were measured at implant and during 12 months of follow-up. P wave sensing was good with both types of leads. Follow-up of these 87 leads showed that both the impedance and threshold increased with the active leads, but not with the passive fixation leads. In the active fixation group, regardless of the high atrial pacing impedance, 93% could still be programmed to 2.5 V-0.6 msec (with a 2:1 threshold safety margin). It is concluded that the high chronic pacing impedance of the active fixation leads will be beneficial on current drain if no major increase in pacing threshold occurs simultaneously.