METHODOLOGICAL AND CLINICAL ASPECTS OF MI NIMIZING POWER-CONSUMPTION IN PACEMAKERS PROVIDING TELEMETRY

In order to minimize power consumption, 30 leads implanted in 17 patie nts with a DDD-pacemaker were investigated using pacemaker telemetry. At charge threshold and at output settings doubling charge threshold, telemetric measurements of pulse amplitude, pulse duration, charge per pulse and average cell current were carried out for voltages ranging from 0.5-4 V. From the mean values of these data, we calculated the rh eobase and chronaxie of the strength-duration curve and determined min imum charge threshold. At a safety margin of 100% of threshold charge, pulse amplitudes with minimum battery drain (U(opt) were linearly rel ated to minimum voltages assuring capture (r = 0.78) and to the rheoba se (r = 0.82). The relative frequency distribution of U(opt) showed pe aks at singular pulse amplitudes. Therefore, programming a safety marg in for pacing by doubling threshold charge should use the lowest pulse amplitude feasible, taking into account advantageous voltages due to output circuitry. Using Lapicque's law to double voltage above thresho ld almost doubles pulse durations (factor 1.8 +/- 0.8) compared to the charge method, increases battery current drain and is therefore not r ecommended.