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Figure 4 Entrainment Mapping in the Same Patient as in Figure 3

(A) The post-pacing interval (PPI) from the ostial aspect of the coronary sinus (CS) is 250 ms, matching the tachycardia cycle length. (B) Entrainment mapping from the distal CS also shows a perfect return cycle. (C) Entrainment mapping from the distal CS after radiofrequency ablation (RFA). Despite a lack of change in the P-wave morphology or the tachycardia cycle length, a long PPI implies that the mitral/distal CS portion of the AT circuit has been eliminated. Also shown are electrocardiographic leads II, V₁, and V₅, and bipolar electrograms recorded by catheters placed in the left atrium (LAd and LAp) and right atrium (RAd and RAp). Os = ostium.