Tracking dynamic conduction recovery across the cavotricuspid isthmus
Dipen C. Shah, MDa,
Atsushi Takahashi, MDa,
Pierre Jaïs, MDa,
Meleze Hocini, MDa,
Jing Tian Peng, MDa,
Jacques Clementy, MDa and
Michel Haïssaguerre, MDa
a CHU de Bordeaux, Hôpital Cardiologique du Haut-Lévêque, Bordeaux-Pessac, France
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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.
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Figure 2 Left, an example of a labile P wave change during RF delivery at a gap site in the isthmus; the negative P wave in leads II, III and aVF changes two beats later to a biphasic P wave with a terminal positivity most prominent in lead II, which persists only for five beats and recovers its previous negative morphology despite continuing RF delivery at the same site with persisting isthmus conduction. Right, stable achievement of the identical P wave change by RF delivery at a nearby site, which was confirmed to be associated with intracardiac evidence of complete isthmus block. The achievement of block results in a terminal positivity of the paced P wave evident in leads II, III, aVF and, less so, in V6 (with the reverse changes as a result of recovery). In both panels, P wave changes are denoted by stars. Time markers are 1 s apart.
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Figure 3 Tracking of dynamic changes in isthmus conduction immediately after termination of clockwise flutter by RF delivery in the isthmus. Top panel (A), pacing from the low lateral RA was initiated 1.5 s after flutter termination and the initial eight paced P waves show a terminal positivity similar to the flutter morphology, but which changes thereafter (star) to a negative deflection. The paced P wave morphology later changed (star) to the same characteristic morphology seen immediately after flutter termination during additional RF applications, as shown in the bottom panel (B), and intracardiac mapping confirmed the achievement of complete isthmus block. This indicates recovery of transient isthmus conduction block after flutter termination despite the continuing delivery of RF energy at the same site. In both panels, arrows indicate the pacing stimulus.
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Figure 4 A summary of the results of P wave tracking of dynamic changes in isthmus conduction as a result of RF ablation. After termination of flutter as a result of ablation, 12 of 15 patients had no block. Further ablation was required to produce stable isthmus block. Conduction recovery after the achievement of complete block across the isthmus occurred in 16 patients, all requiring further ablation. See text for details.
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Figure 5 Time course of P wave and isthmus conduction recovery after initial achievement of block. Twenty-five instances occurred in 16 patients, with the majority occurring in up to 60 s.
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