Bachmann's Bundle‐Related Atrial Tachycardias Following Catheter Ablation of Persistent Atrial Fibrillation

Figures

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  Figure 1. Flowchart showing the course of the study patients.

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  Figure 2. Real‐time impedance and pouch. While mapping an atrial tachycardia (AT) involving the anterior left atrium (LA) with the ablation catheter (arrow, panel A), there is a sudden rise in the real‐time impedance from about 125 ohms to 150 ohms (arrow, panel B), suggestive of a pouch in the region of Bachmann's bundle (BB). Note that mapping accounted for 98% (293/300 ms) of the tachycardia cycle length (TCL), consistent with macro‐reentry. LS, left superior; LAA, left atrial appendage; PV, pulmonary vein; RS, right superior.

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  Figure 3. Oblique perimitral reentry. (A) An activation map showing an example of an oblique variant of perimitral atrial flutter in a patient with prior LAA isolation. In this case, the reentrant circuit does not involve the anterior annulus, in contradistinction to classic perimitral reentry, and instead the circuit is completed at the region of BB. The numbers on the map refer to the difference between the post‐pacing interval and the TCL during entrainment mapping. Note the very long return cycle ( + 120 ms) at the anterior annulus (See Figure 2B). RI, right superior; LI, left inferior. (B) Shown are the results of entrainment mapping from the same patient whose activation map is shown in Figure 3A. The post‐pacing interval from the anterior LA (near Bachmann's bundle region) and the lateral mitral isthmus show an in‐circuit response, consistent with macro‐reentry. However, the very long return cycle at the anterior mitral annular region rules out conventional perimitral reentry. Abl, ablation; CS, coronary sinus; MA, mitral annulus.

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  Figure 4. Response to radiofrequency ablation (RFA) ablation at the BB region for oblique perimitral reentry in the same patient whose map and tracings are shown in Figure 3A,B. (A) RF energy delivery slows the AT from 280 ms to 300 ms, but without tachycardia termination. (B) Ongoing energy delivery paradoxically accelerates the tachycardia from 300 ms to 220 ms. (C) Prolonged energy application again slows the tachycardia, finally terminates the AT to sinus rhythm.

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  Figure 5. Anterior LA and BB block during sinus rhythm (SR). (A) A widely‐split double potential was recorded at the high anterior wall of the LA from the same patient whose maps and tracings are shown in Figures 3 and 4. The initial smaller electrogram (arrows) represents far‐field right atrial activation (note that it precedes the onset of the p‐wave), and the second signal, local LA activation. (Note that the anterior LA is activated well after the coronary CS). (B) An activation map during SR shows that interatrial activation proceeds via the fossa as opposed to BB, consistent with BB block. As a result, BB is activated in a caudocranial fashion. In the presence of conduction block at the anterior wall as well, high anterior LA (purple region) is activated after the lateral LA. The dashed arrow represents activation along the ridge (between the isolated LAA and the left PVs). Note the LA activation time is very prolonged at 177 ms.

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  Figure 6. An example of biatrial tachycardia that required ablation at both right (RA) and left atrial aspects of BB. (A) Entrainment mapping from the septal aspect of the base of RA appendage (RAA) shows that this site is a component of the reentrant circuit. (B) An activation map shows that the earliest breakthrough occurred at the septal RA/superior vena cava (SVC) junction, the site corresponding to the right atrial endocardial projections of BB. Note that only a fraction of the tachycardia cycle length (39%) could be accounted for with activation mapping. (C) A prolonged RF energy application at the septal RA/SVC junction (jx) only slows the tachycardia from 400 ms to 430 ms (see next figure).

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  Figure 7. Continued from Figure 6. Slowing and termination of biatrial AT at anterior LA. (A) Since the AT did not terminate during RA ablation, additional ablation was performed at the LA aspect of BB, which further slowed the tachycardia from 420 ms to 490 ms. (B) Additional ablation was required at the high anterior LA for termination despite the absence of a local electrogram (see panel C). (C) Despite high gain setting, no obvious local electrogram is apparent (other than baseline wander/artifact) at the site where RFA terminated the tachycardia to sinus rhythm (see next figure).

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  Figure 8. (A) A biatrial map showing components of the reentry circuit (gold tags), sites that slowed AT (yellow tag) and the site that finally terminated AT (orange tag) in the same patient as in Figures 6 and 7. The orange circle represents the epicardial location of Bachmann's bundle. Green tags represent the site of the RA lead. (B) An anatomic specimen showing the relationship of Bachmann's bundle to the LA and the RA. (Modified with permission from Kuhne et al, reference number 12 [6]).(C) Fluoroscopic views showing the location of the ablation catheter in the LA (arrow) where RF ablation terminated the tachycardia. AO, left anterior oblique; AP, anteroposterior; LICD, implantable cardioverter defibrillator generator.

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  Figure 9. An example of a focal AT from BB region. (A) An activation map shows radial spread from the site of origin at BB. Despite a cycle length of 330 ms, only 122 ms (37%) could be accounted for consistent with a focal mechanism. (B) The electrogram recorded at the site where RFA terminated the tachycardia shows that the local signal precedes the surface p‐wave by 30 ms. Note that a Q‐wave (arrow) is recorded on the unipolar electrogram, again confirming the site of origin.

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  Figure 10. Pouch at the BB region. (A) A computed tomographic axial reconstruction showing a large pouch (arrows) at the region of Bachmann's bundle (BB). Ao, aorta. (B) A 3D anatomic map of the LA during RFA from another patient. As the catheter (black arrow) was deflected anteriorly, it suddenly dislodged, prompting immediate discontinuation of energy delivery (see next). (C) Note the very high contact forces (> 75 g) encountered upon catheter dislodgement into the pouch.