DETERMINANTS OF DUAL-CHAMBER PULSE GENERATORS LONGEVITY

The aim of this study was to investigate the effect of battery capacit y internal current drain, and stimulation energy on pulse generators l ongevity, and if battery impedance measurements can reliably predict p ulse generators end-of-life. For this purpose, the records of 577 pati ents with a mean age of 65 +/- 14 years who had undergone implantation of two different dual chamber pulse generators (PG1:409; PG2:168) wer e retrospectively reviewed. Battery capacity were 2.3 Ah (PG1) and 3.0 Ah (PG2) while current drain at comparable nominal settings was 20 mu A (PG1) and 30 mu A (PG2) indicating a higher internal current drain of PG2. After a mean follow-up of 46 +/- 23 months, stimulation energy at reprogrammed output settings was significantly higher in PG1 as co mpared to PG2 (17.1 +/- 0.14 J vs 15.5 +/- 0.24 J). Three PG1 (0.7%) a nd 12 PG2 (7.1%) (P < 0.02) had to be exchanged after a mean of 77.3 /- 5.3 months (PG1) and 75 +/- 13.5 months (PG2) (P = NS) due to end-o f-life being reached. The difference in battery impedances of PG1 and PG2 gained statistical significance 5 years after implantation (1.0 k Ohm vs 2.4 +/- 6.7 k Ohm) preceding the significant difference in PG s urvival after 6 years (98.7 +/- 1.3% vs 90.7 +/- 4.8%). These results indicate that internal current drain is the most important determinant of the pulse generators longevity and that battery impedance can reli ably predict end-of-life. Therefore, the essential information about i nternal current drain should be available for each pacemaker, since it is required for adequate pulse generator selection. Diagnostic functi ons of dual chamber pulse generators should include measurement of bat tery impedance.