Amplitude of atrial electrical activity during sinus rhythm and during atrial flutter-fibrillation.

The onset of atrial flutter or fibrillation in a patient with a DDD pacemaker may result in sensing of the atrial arrhythmia and an inappropriate ventricular pacing response. In order to assess the potential of this problem, we evaluated the amplitude of atrial electrograms recorded from the right atrial appendage during sinus rhythm and during atrial flutter or fibrillation during 19 episodes in 18 patients. In 11 episodes of fibrillation and eight episodes of flutter, there was no difference in amplitude of either unipolar or bipolar atrial electrograms compared to that recorded during sinus rhythm (p greater than 0.05). In 14 of 19 episodes, the direction of depolarization of the bipolar electrogram did not change appreciably between sinus rhythm and the atrial arrhythmia. In summary, there is insufficient difference between amplitude of atrial depolarizations recorded during sinus rhythm and atrial flutter or fibrillation to be differentiated reliably by DDD pacemakers.