A study on electrocardiographic changes during long-term cardiac pacing.

This report describes the clinical evaluation of chest wall stimulation (CWS) follow-up studies in patients implanted with pacemakers and the value of this method for the observation of intrinsic rhythm. The CWS method was used to periodically check the intrinsic rhythm in 25 long-term pacemaker cases with atrioventricular block. After an average of 26.6 months, an improvement of conduction disturbance was seen in four cases (16 per cent), aggravation was noted in 11 cases (44 per cent), and no change was found in 10 cases (40 per cent). In five patients exhibiting aggravation, no intrinsic rhythm could be detected. Improvement was noted only in atrioventricular and not in intraventricular conduction. Six generators with demand failures were also detected during the course of this study.