Natural evolution of atrioventricular conduction in patients with sick sinus syndrome treated by atrial demand pacing. A study of 26 cases.

The authors have followed up 26 patients with sinus node disease who were treated by atrial pacing. The follow-up duration varies between 10 months and 3 years. Assessment of A.V. conduction was performed repeatedly by atrial pacing at increasing rates. Nine patients showed a progressive, sometimes early, deterioration of their A.V. conduction system; five (19%) developed second degree A.V. block of Mobitz type I for pacing rates lower than 100 beats/min. In three of them, the pace-maker had to be replaced by a dual chamber stimulator. Deterioration of A.V. conduction seems to be more frequent in subjects with antecedents of myocardial infarction (4/5) than in others (5/21: p less than 0.05). Deterioration of A.V. conduction is not uncommon among patients with sinus node dysfunction, especially after myocardial infarction. This constitutes a serious limitation to the use of atrial pacing.