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Figure 2 Identification of Origin of PV Trigger

Panels A and B show surface electrocardiographic (ECG) tracing and recordings from circular mapping, ablation, coronary sinus, and posterior right atrium–superior vena cava catheters. Panel E is a detailed image from panel B, showing the activation sequence of the trigger inducing atrial fibrillation. Red arrows point to the earliest electrogram, which corresponds to bipole 7 to 8 of the circular catheter. Activation in the ablation catheter is almost as early as in the earliest bipole of the circular catheter. The blue arrow identifies the distal bipole of the coronary sinus catheter. Of note, there is bracketing in the activation sequence during the trigger beat, suggesting an origin in the left PVs. Panels C and D are right anterior oblique (RAO) and LAO fluoroscopic projections, respectively, showing the placement of the catheters during the initiation of the atrial fibrillation. The trigger arose from the superior-posterior segment of the left superior PV, corresponding to the location of bipole 7 to 8 of the circular mapping catheter. Abbreviations as in Figure 1.