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Transverse conduction capabilities of the crista terminalis in patients with atrial flutter and atrial fibrillation

^a Department of Cardiology, University of Bonn, Bonn, Germany

View larger version (68K): [in a new window]   Figure 1 A 60° right anterior oblique (A) and a 30° left anterior oblique (B) fluoroscopic view of the heart showing typical positions of the intracardiac echocardiographic catheter (ICE), the mapping catheter along the crista terminalis (CTMap) and the pacing catheter approximately 0.5 to 1.0 cm anteriorly to the crista terminalis (Pace).

View larger version (52K): [in a new window]   Figure 2 Intracardiac ultrasound images demonstrating the localization of the crista terminalis (CT) as well as an adequate (A) and an inadequate (B) position of the crista terminalis mapping catheter (Map) during a typical investigation. Images were obtained at the mid-right atrium inferior to the entrance of the right atrial appendage. Orientation of the images is labeled on top. IAS = interatrial septum; ICE = artifact of the intracardiac ultrasound catheter.

View larger version (26K): [in a new window]   Figure 3 Recordings obtained during programmed stimulation in sinus rhythm (baseline cycle length S1–S1, 500 ms) approximately 0.5 cm anterior to the crista terminalis at bipole 1/2 of the pacing catheter (Patient #10). The surface leads I, II and III and the intracardiac electrograms recorded at successive bipoles of the pacing (Pace) and the crista terminalis (CT) mapping catheter are shown. Bipole 1/2 refers to the most superior and bipole 9/10 to the most inferior pair of electrodes. Catheter position as in Figure 1. (A) Baseline pacing with a pacing cycle length S1–S1 of 500 ms as well as an atrial premature beat with a coupling interval S1–S2 of 430 ms resulted in continuous electrograms at all bipoles of the CT catheter. The width of local activation was relatively short, for example, 50 ms at bipole CT1/2. The atrial activation at the CT showed a sequence from the pacing site at the superior aspect of the right atrium toward the inferior right atrium (arrows). (B) A decrease of the coupling interval S1–S2 from 430 to 310 ms resulted in a significant prolongation of local activation, for example, from 50 ms to 80 ms at bipole CT1/2, indicating a conduction delay. Two components (A and B) of the fractionated potentials could be distinguished. However, no isoelectric interval was present and the activation sequence remained unchanged. (C) After extrastimulus testing with a further 20 ms decrement of the coupling interval (S1–S2, 290 ms), local electrograms at the CT mapping catheter showed a marked prolongation, for example, 105 ms at bipole CT1/2, and the two components became separated by an isoelectric interval. With the occurrence of split potentials, a marked alteration of the activation sequence of the second component of split potentials was found. As can be appreciated from these findings, a conduction block developed at the CT mapping catheter that was not present during atrial premature beats with longer coupling intervals.

View larger version (29K): [in a new window]   Figure 4 Recordings obtained during programmed stimulation in sinus rhythm (baseline cycle length S1–S1, 600 ms; coupling interval S1–S2, 250 ms) at bipole 1/2 of the pacing catheter (Patient #6). Surface leads I, II and III and intracardiac electrograms recorded at successive bipoles of the pacing (Pace) and the crista terminalis (CT) mapping catheter are shown. Bipole 1/2 refers to the most superior pair of electrodes, bipole 9/10 to the most inferior. Catheter position as in Figure 1. Baseline pacing resulted in the occurrence of broad but continuous atrial activation at all CT mapping bipoles, suggestive for transverse pulse propagation across the CT. After extrastimulus testing with a coupling interval of 250 ms, split potentials with an isoelectric interval were recorded, indicating a functional conduction block at the CT. The first component of the split potentials represents the depolarization of the anterior aspect of the CT, the second component that of the posterior aspect, respectively. In the presence of conduction block, the pulse propagation at the posterior right atrium shows a sequence from low to high (arrow). Two components (A and B) of the fractionated potentials could be distinguished.

View larger version (29K): [in a new window]   Figure 5 Recordings obtained during programmed stimulation in sinus rhythm (baseline cycle length S1–S1, 500 ms; coupling interval S1–S2, 190 ms) at bipole 9/10 of the pacing catheter (Patient #11). Recordings, abbreviations and catheter position as in Figure 4. In this example, occurrence of a functional conduction block at the CT resulted at the posterior right atrium in a pulse propagation from high to low (arrow).

View larger version (33K): [in a new window]   Figure 6 Recordings obtained during programmed stimulation in sinus rhythm (baseline cycle length S1–S1, 500 ms; coupling interval S1–S2, 330 ms) at bipole 5/6 of the pacing catheter (Patient #7). Recordings, abbreviations and catheter position as in Figure 4. This figure illustrates a typical example of a localized conduction block at the central aspect of the CT. As can be seen, baseline pacing at bipole 5/6 results in a spread of activation from the pacing site toward both edges of the CT mapping catheter. After extrastimulus testing with a coupling interval of 330 ms, split potentials were recorded at bipole 5/6 and bipole 7/8 of the CT mapping catheter. The activation sequence of the first component of split potentials was identical to that during baseline pacing. However, the activation sequence of the second component indicated two wavefronts colliding at bipole 5/6. The descending wavefront emerges from bipole 1/2, the ascending wavefront from a site inferior to bipole 9/10.