title: The A-R interval as exercise indicator: a new option for rate adaptation in single and dual chamber pacing.
abstract: We investigated the possibility to use the interval from an atrial stimulus to the ventricular R wave (A-R interval) as an indicator of physical stress, in 16 patients with pacemakers implanted for severe atrial bradycardia but with intact AV conduction. The A-R interval was studied during incremental atrial pacing at rest and during exercise with a constant workload. In addition, the atrial pacing rate was kept constant just above spontaneous sinus rate and the dynamics of the A-R interval were studied during exercise with a low constant workload and during a maximal exercise test with increasing workload. Incremental atrial pacing prolonged the A-R interval and this response was blunted during exercise (P less than 0.003). Atrial pacing at a constant rate and during a constant workload resulted in an almost direct shortening of the A-R interval. When the workload was increased but the atrial rate kept constant, a pronounced shortening of the A-R interval was noted (P less than 0.0001). It is concluded that changes of the A-R interval during different kinds of exercise were prompt and predictable in patients with sinus node dysfunction but intact AV conduction. In these patients the shortening of the A-R interval during exercise may be a suitable indicator for rate adaptive atrial pacing.
authors.affiliation: Department of Cardiology, Medical Centre Alkmaar, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: Ruiter
authors.forename: H
authors.initials: H
authors.lastname: de Boer
authors.forename: M J
authors.initials: MJ
authors.lastname: Begemann
authors.forename: R
authors.initials: R
authors.lastname: van Mechelen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000503:physiopathology / Q000628:therapy*; D001283:Atrioventricular Node / Q000503:physiopathology; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial