TELEMETRY GUIDED PACEMAKER PROGRAMMING - IMPACT OF OUTPUT AMPLITUDE AND THE USE OF LOW-THRESHOLD LEADS ON PROJECTED PACEMAKER LONGEVITY

In a prospective study a low threshold screw-in electrode (Medtronic 5 078, group I, n = 9) was compared to a conventional active fixation le ad (Biotronik Y60BP, group II, n = 9) to investigate whether lower pac ing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connect ed to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294-03) in both groups. Eighteen months after implantation, atrial an d ventricular pacing thresholds were measured as the charge delivered per pulse [mu C] at 0.5, 1.0, 1.5, 2.0, and 3.5 V, respectively. For c hronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently program med to 2.0 V with the double of the charge threshold as the safety mar gin for pacing (''safety charge''). A combination of atrial and ventri cular output settings rr as optimal, if it resulted in minimum battery current drain [mu A] as measured by pacemaker telemetry. In both grou ps, current consumption [mu A] decreased significantly as output ampli tude was decreased, exhibiting its lowest value at 1.0 V in either cha nnel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 ''safety charge'' val ues ere almost identical, the ventricular channel essentially contribu tes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration o f 0.42 +/- 0.15 ms. In group 2, however, ever, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 +/- 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 +/- 0.63 mu A in group 1 v ersus 14.42 +/- 0.32 mu A in group 2 (P < 0.001). As patients were chr onically programmed to these output settings, this difference translat es into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3 % (121 +/- 4 vs. 104 +/- 2 months; P < 0.001). Thus , programming a 2:1 safety margin in terms of charge and optimizing th e output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of m odern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a signifi cant prolongation of projected pacemaker service life which is of grea t importance with the increasing awareness of health care expenditures . The gain in projected longevity is mainly due to the option of reduc ing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.