The patient alert system--pilot study of built-in warning systems for pacemakers.

Malfunction of a pacing system can be life-threatening for a pacemaker-dependent patient. It would be desirable for implantable pulse generators to have a built-in automatic warning system capable of alerting the patient as soon as a potentially dangerous disorder is detected. In this study, seven patients (mean age, 72.6 +/- 10.7 years) with slow, chronic atrial fibrillation underwent implantation of a dual-chamber pulse generator with a custom-made "alert electrode" connected to the atrial port of the pulse generator to stimulate the underlying pectoral muscle. The muscle was temporarily stimulated while the pacemaker was in VVIR mode. The lowest amplitude sufficient to alert the patient (perception threshold) was 1.6 +/- 0.58 V at 0.45 ms during implantation and 1.2 +/- 0.5 V at 0.45 ms chronically. In a second phase, alerts outside of the office were issued using a special software routine capable of delivering stimuli at programmable date and time.