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. The mean time to explant for generator malfunctions was 42 months and for all pacing system malfunctions it was 38 months compared to 31.9 months and 28.6 months, respectively, for the 2,402 dual chambered units that were observed for 38,718 months. In the single chambered units, the most frequent reason for explant was battery exhaustion (37% of explants) followed by lead problems (26%) compared to 49% and 12%, respectively, for the dual chambered units. The incidence rates, defined as a transtelephonic test result, required physician decision for action or clarification of the pacing mode or program parameters and showed a high incidence rate immediately post-implant; thereafter, there was a relatively trouble-free period until the 36th month when capture, sensing, and battery problems began to occur at a steady rate reaching 4% at the end of 48 months. Similarly, for dual chambered units, an 8% incidence rate was seen within the first 3 months, followed by a quiescent period until the 28th month when the incidence rate jumped to 16%.(ABSTRACT TRUNCATED AT 250 WORDS)