Clinical experience with a bradycardia indicating pacemaker.

The beneficial effect of permanent pacing is controversial in certain patient groups. Once pacing has been instituted it is seldom terminated and an evaluation of pacemaker dependence is therefore not possible. An implantable pulse generator, detecting bradycardia below 30 bpm has been developed in order to broaden our knowledge about the natural history of bradyarrhythmias treated by permanent pacing. This pacemaker has been implanted in 38 patients who did not have clear-cut indications for permanent pacing. They have been followed for a mean of 13 months. Bradycardia was detected in 33 patients 1 to 21 months (4.6 mean) after implantation. Twenty-one patients did not have a detected bradycardia for long periods (months-years). Minor symptoms of lightheadedness attributable to bradycardia were reported by 15 patients during periods when the pacemaker had been activated. Holter monitoring for at least 24 hours was carried out in all patients and electronic analysis of explanted generators was performed in eleven cases. No technical failure related to the bradycardia-detecting facility was observed. The combination of diagnostic and therapeutic properties in the bradycardia-indicating pacemaker provides means for safe evaluation of pacemaker dependency over long time periods in patient groups with controversial indications for permanent pacing.