Abstract
Transient pervenous bifocal (sequential atrioventricular) demand pacing was performed in ten patients. Six had chronic conducting system disease and four acute myocardial infarction. The control electrocardiograms showed different degrees of coexisting, alternating or intermittent sinoatrial slowing and AV block. This modality of electrical stimulation was achieved by the combination of QRS-inhibited ventricular demand pacing with QRS-inhibited atrial demand stimulation. In the presence of atrial bradycardia and normal AV conduction only the atria were stimulated. When sinus slowing was associated with AV block, both atria and ventricles were paced. A double electrode system was required for the restoration of AV synchronization. Consistent atrial capture was achieved by means of a J-shaped endocardial bipolar electrode. Permanent bifocal demand pacing has also been used in three patients with satisfactory results. Although both the concept and applicability of bifocal demand pacing were proved, further studies are required to assess the optimal AV sequential interval as well as the long-term electrical reliability and hemodynamics benefits.
