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Figure 1 An example of labile intermittent conduction through a discrete "gap" in the ablation line, reflected both in the local intracardiac electrograms and recovery of the P wave change on the surface ECG. Lead II is shown here, and for the first two paced atrial beats, the P wave shows terminal positivity correlating with a late (second) potential (at 160 ms after the stimulus artifact) on the ablation line and an "r" wave on the unipolar electrograms. The local bipolar electrograms are abruptly transformed into a fractionated continuum with an activation time of 85 ms for the next two beats (stars), accompanied by a QS pattern on the unipolar electrograms and recovery of the P wave with a double negative deflection. This example provides a clear demonstration of the dynamic association between the recovery of cavotricuspid isthmus conduction and P wave recovery.