Alternative atrial pacing site to improve cardiac function: focus on Bachmann’s bundle pacing

Figures

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  Figure 1. Electrocardiogram (ECG), intra-cardiac electrogram, and echo trans-mitral Doppler before and after implantation of a Bachmann’s bundle pacing lead. (A) Sinus rhythm P wave duration is prolonged at 129 ms. (B) Bachmann’s bundle pacing shortened the P wave duration to 86 ms while preserving the PR interval (204 vs. 208 ms). (C) Separation of E and A waves with the A wave occurring late and truncated by ventricular systole (heart rate 54 bpm). Diastolic mitral regurgitation is also seen. (D) With Bachmann’s bundle pacing, the A wave is complete before ventricular systole (heart rate 60 bpm).

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  Figure 2. Sinus rhythm, right atrial appendage paced, and Bachmann’s bundle-paced P wave morphologies in a patient with non-ischemic cardiomyopathy undergoing primary prevention implantable cardioverter defibrillator implant. Compared with sinus (A), right atrial appendage pacing (B) produces a low amplitude, prolonged P wave (150 vs. 116 ms) with prominent negative forces in V1, and increases the PR interval (198 vs. 178 ms), whereas Bachmann’s bundle-paced P wave (C) is similar to but narrower than sinus (95 ms), with a shorter PR interval (159 ms).

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  Figure 3. Pre-shaped delivery catheters (C315-J and C315-S5, Medtronic, Minneapolis, MN, USA) for delivery of the 3830 lead (Medtronic, Minneapolis, MN, USA) to the Bachmann’s bundle area. Courtesy of Medtronic.

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  Figure 4. Final position of a stylet-driven atrial lead at Bachmann’s bundle in postero-anterior (PA, left), LAO 40° (center), and RAO 30° (right) projections. In the PA view, the site of the atrial lead tip resembles a position in the right atrial appendage. However, there is no windscreen wiper movement. In this very large right atrium, the corner between the right atrial roof and the right side of the atrial septum is leftward (posterior) to the His bundle lead which serves as an approximate landmark for the plane of the interatrial septum. In RAO, the atrial lead at Bachmann’s bundle points perpendicularly to the roof of the right atrium.

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  Figure 5. Pacing at 5 V/0.5 ms (first P wave) and 1 V/0.5 ms (third P wave; the second is superimposed on the T wave) showing an inferior axis P wave consistent with capture of Bachmann’s bundle area but without significant change in P wave morphology or latency.

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  Figure 6. Decremental threshold testing from 1 V/0.5 ms to 0.9 V/0.5 ms results in increased latency and the emergence of a separate EGM (arrowhead) representing local RA activation and timing with the start of the P wave. This suggests Bachmann’s bundle is selectively captured. We observe this phenomenon in a minority of cases.

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  Figure 7. Surface ECG and unipolar EGM from the lead tip after implantation of a Bachmann’s bundle lead (A). The first beat is a sinus beat. The EGM consists of a large right atrial component followed by a low amplitude but sharp component, followed by far-field left atrial EGM. The second and third P waves are premature atrial complexes, in which the small sharp EGM is earliest (arrowhead), followed by the RA and LA components. The P wave, EGM sequence, and stim-P wave time are strikingly similar to that produced by pacing from the lead tip (B), suggesting that pacing selectively captures the low amplitude sharp component and that this represents activation of Bachmann’s bundle.