[Some aspects of energy-saving pacing in the light of the author's studies]

Pacemaker working time, which was in the beginning not more than one year, reached the maximum in the first half of the 70s, then shortened to between a few to several years. Aim of the study was investigated the electrical properties of the endocavitary pacemaker leads, considered the possibility of manufacturing a longlasting pacemaker ("lifetime pacemaker") and examined the preference of patients in relation to dimensions of the implanted device.

The investigation included 190 electrodes with cathodes coated with titanium nitride (TIJ and TIR), 244--coated with iridium (SXA and SXV) and 90--coated with black platinum (DXA and DXV). A formula was developed to calculate the estimated pacemaker longevity: Longevity (years)=Qog (Ah)x10(6)/8760x[Isp (μA)+Ist (μA)], where Qog is the capacity of the electric cell, Ist--current stimulation, Isp--quiescent current of the generator. The survey was performed in a group of 145 patients with pacemakers, using an original questionnaire.

All the tested electrodes manifested a good acute and distant pacing threshold and the small intra-electrode differences were not clinically significant. In distant measurement, the average rheobasis of the steroid platinum electrode was 0.59 V and the chronaxie was 0.23 ms. These parameters have direct impact on modern pacemaker programming methods. It was proven that increasing the electric cell capacity in the DDD pacemaker by every one-tenth of ampere-hours caused a significant increase in the working time (p=0.000). Thus, the increase of the electric cell capacity allows for returning to the concept of a "lifetime pacemaker". The results of the survey showed that patients were willing to accept larger, but longlasting pacemakers (p=0.000).

The tested passive and active electrode with a fractalcoated cathode ensured good electrical parameters within several months of observation. The electrode equipped with dexamethasone deposit showed no advantage in terms of the stimulation threshold when compared to the passive electrode coated with titanium nitride. Significant differences in the pacing threshold, which were detected between the leads with different cathode coatings, had little effect on pacemaker longevity. The most extensive impact on the generator longevity was exerted by the capacity of the electrical cell and pacemaker quiescent current. Patients were able to accept a much larger device than currently produced providing a long working time was ensured.