Unipolar potential voltage mapping of bachmann's bundle during different stages of atrial fibrillation: a novel target for ablation therapy?

Bachmann’s Bundle (BB) plays an important role in the pathophysiology of atrial fibrillation (AF). Because of its parallel fiber arrangement, BB may be more susceptible to remodeling, which may increase the risk for AF. Low-voltage areas (LVA) are indicators of remodeling and have emerged as important targets for AF ablation therapy. At present, there is no data on features of electrical remodeling at BB during the different stages of AF.

To investigate the spatial distribution of LVAs at BB during different types of AF, including induced and (longstanding) persistent AF.

High resolution epicardial mapping (192 electrodes; interelectrode distance 2 mm) at BB was performed during AF for 10 seconds in patients (n= 42) who underwent elective cardiac surgery. The study population consisted of 16 patients without and 25 patients with spontaneous AF, ranging from one week to 39 years. When the initial rhythm was sinus rhythm, AF was induced by programmed electrical stimulation. For each patient, the median, 5th percentile (P5) and 95th percentile (P95) and the difference between the P5 and P95 of all unipolar potential voltages were calculated. LVAs were defined as areas with a peak-to-peak amplitude <1 mV. After comparing induced AF with spontaneous AF, a separate correlation analysis was conducted within the spontaneous AF group.

Within the induced AF group, the median potential voltages ranged from 0.87 to 3.50 mV, whereas in the spontaneous AF group it ranged from 0.38 to 2.62 mV. Median potential voltages were lower in the spontaneous AF group compared to the induced AF group (0.88 ± 0.47 mV vs 1.74 ± 0.64 mV; p<0.01). The P95 of all potential voltages was significantly lower in patients with spontaneous AF compared to induced AF (3.08 vs 5.96 mV; p<0.01). Also, the spontaneous AF group had less potential voltage variation (2.76 mV vs 5.48 mV; p<0.01) and a higher proportion LVAs (61.5% vs 30.2%; p<0.01). The proportion of LVAs did not increase in patients with a longer history of AF (r=-0.26; p=0.21).

Spontaneous AF is associated with lower median potential voltages, less voltage variation and increased LVAs compared to induced AF. Interestingly, the prevalence of LVAs did not increase during progression of AF. During substrate-based ablation approaches targeting LVAs, BB should be considered as part of the treatment strategy.