Problems and anti-tachyarrhythmic effects of chronic atrial pacing

Sixty-six patients in whom atrial pacemaker (AAI) were implanted were followed for one year to 5 years for the occurrence of pacing failure, sensing problems, and later AV block. Pacing failure occurred in only one patient and sensing problems occurred in 15 patients but 10 of them improved after a change of sensing. Temporal change of AV conductivity was not recognized in the majority of patients. Eighteen patients developed transient decrease in AV conductivity. Two patients developed persistent decrease in AV conductivity and ended in clinical AV block for which the pacemaker was implanted. Out of 66 patients, 22 had a history of paroxysmal atrial flutter or fibrillation (AFF) prior to AAI implantation. They were divided into two groups. Group I consisted of 20 patients in whom paroxysmal AFF disappeared after AAI implantation. Group II consisted of 22 patients in whom paroxysmal AFF persisted after AAI implantation. Electrophysiological studies prior to the AAI implantation showed that sinus rate at control was significantly slower (36.3 +/- 10.1 beats per min in Group I, 57.1 +/- 10.8 beats per min in Group II), atrial fragmented activity zone was significantly narrower (62.7 +/- 32.9 msec in Group I, 88.1 +/- 19.7 msec in Group II), and the occurrence of PAC was less at an atrial pacing rate of 70 beats per min (8% in Group I, 67% in Group II) in Group I compared to Group II.(ABSTRACT TRUNCATED AT 250 WORDS)