Transtelephonic monitoring of 25,919 implanted pacemakers.

In order to evaluate the behavior of lithium-powered cardiac pacemakers, a database of 25,919 lithium-powered pacing systems including 23,517 single and 2,402 dual chambered pacemaker generators were followed in 21,750 patients. Of this group, 11,319 were currently active in addition to 7,560 who died, as well as 2,871 patients who terminated their follow-up service prior to the end-of-life of the pacemaker system. A total of 23,517 single chambered pacemakers were followed for 719,173 months of pacing.

Longevity comparisons among lithium anode power cells for cardiac pacemakers.

Of over 10,000 lithium-powered pacemakers followed by a commercial transtelephone monitoring service, 148 have been explanted due to rate decline. A breakdown according to the power cell manufactures shows that the longevity is not uniform, indicating that significant differences exist among the power cell designs even though all have lithium anodes. One tenth of all lithium-powered pacemakers in the study were explanted for rate declines within 4 years.

A comparison of unipolar and bipolar electrograms for cardiac pacemaker sensing.

Simultaneous unipolar and bipolar electrograms were recorded and compared from 49 pacemaker patients with bipolar endocardial electrodes. Average bipolar depolarization signal voltage equalled that of unipolar but showed greater variation. Bipolar and unipolar slew rates were equal in both mean and variance.

The ventricular endocardial electrogram and pacemaker sensing.

During cardiac pacemaker implantation and pulse generator replacement, unipolar, right ventricular electrograms were recorded from 133 patients (77 at implantation and 56 at pulse generator replacement) at 200 mm. per second with a band pass of 0.1 to 2,000 Hz on photographic paper.

Endocardial electrograms and pacemaker sensing.

Endocardial electrograms in 77 acute cases (at time of pacemaker implant) and 56 chronic cases (at time of pulse generator replacement, with electrodes in service for at least 6 months) were recorded. The peak-to-peak voltage and rate of rise, or slew rate, were compared acutely and chronically. Both parameters must simultaneously exceed given thresholds to trigger the sensing circuits of implantable pacemakers.

Pulse duration variation and electrode size as factors in pacemaker longevity.

For the past 4 years, we have used highly efficient Medtronic electrodes (Nos. 6901 and 6907), with small surface areas, for cardiac pacemakers. We have found that chronic thresholds average 1.