Relation between the widening of the fragmented atrial activity zone and atrial fibrillation

Fragmented electrical activity is often recorded by a local atrial electrogram in response to atrial extrastimuli. To assess the relation between fragmented activity and the spontaneous occurrence of atrial fibrillation or flutter (AFF), the fragmented activity zone was measured in 57 patients. The electrograms of the high right atrium, low right atrium and left atrium (through the coronary sinus) were recorded simultaneously during high right atrial stimulation. The fragmented activity zone was defined as the S1-S2 interval (S1 = stimulus of a basic beat, S2 = stimulus of a premature beat) during which a significant fragmented activity was recorded by a high right atrial electrogram after S2. Fifteen patients had neither sinoatrial disease nor atrial arrhythmias (Group I, controls), 16 had sick sinus syndrome (SSS) with a history of paroxysmal AFF (Group II), 14 had SSS without a history of paroxysmal AFF (Group III), and 12 had idiopathic paroxysmal AFF (Group IV). The fragmented activity zone was significantly wider in Group II (112 +/- 26 ms [mean +/- standard deviation], p less than 0.001), Group III (77 +/- 38 ms, p less than 0.001) and Group IV (86 +/- 19 ms, p less than 0.001) than in Group I (31 +/- 25 ms). Patients in Group II had a wider fragmented activity zone than those in Group III (p less than 0.01). Thus, the widening of the fragmented atrial activity zone is characteristic of AFF and may be a good index of a tendency to develop spontaneous AFF.