Introduction and objectives: Contemporary atrial pacemakers incorporate pacing modes for treating atrial arrhythmias. Because atrial fibrillation in the right atrium can exhibit an organized pattern, it can be difficult to differentiate from atrial flutter. We assessed criteria for discriminating between atrial flutter and organized atrial fibrillation when using a bipolar electrode in the right atrium.
Methods: Simultaneous bipolar electrograms of the right and left atria were obtained in 45 patients: Group I comprised 15 patients with atypical flutter, Group II comprised 15 with typical flutter, and Group III, 15 with organized atrial fibrillation in the right atrium. The mean cycle length and the mean variation in cycle length observed over 15 seconds in electrograms of the right atrium were recorded.
Results: The mean cycle length was longer in Groups I and II than in Group III (232 [21] ms and 234 [24] ms, respectively, versus 183 [16] ms; P< .001). The mean variation in cycle length was less in Groups I and II than in Group III (16 [7] ms and 13 [4] ms, respectively, versus 22 [7] ms; P< .01). A cycle length > or =203 ms discriminated atrial flutter from atrial fibrillation with a sensitivity of 97% and a specificity of 87%. A cycle length variation < or =18 ms discriminated atrial flutter from atrial fibrillation with a sensitivity of 70% and a specificity of 80%.
Conclusions: Cycle length was better than the variation in cycle length for differentiating atrial flutter from organized atrial fibrillation.