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Figure 5 Analysis of consecutive activation patterns during a representative episode of initiation of atrial fibrillation (AF) induced by extrastimulation from A 1–2. (A) Pulmonary vein recordings from a basket catheter placed in the left superior pulmonary vein from the same patient as shown in Figure 4. After extrastimulus S2 of 200 ms, AF is induced. The numbers identify the conduction times from S2. a = far-field atrial potential. (B) A total of 600 ms of data (six consecutive time windows) from an initiation of the episode is analyzed. The star indicates the pacing site (A 1–2). Dark gray regions indicate areas that were not activated during a 100-ms window. The dashed line indicates a line of functional block. In this case, a re-entrant circuit involving the exit breakthrough point (splines B and C) and the entrance breakthrough point (spline H) starts AF. Wave fronts traveling to and from the left atrium may play an important role in reformation of activation. However, no re-entrant circuits only within the pulmonary vein are observed.
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