High-density evaluation of the arrhythmogenic substrate in persistent atrial fibrillation

Background

Left atrial (LA) fibrosis is a key component of arrhythmogenic remodeling in atrial fibrillation (AF). LA low-voltage areas (LVAs) are considered surrogates for fibrosis and novel targets for ablation. However, there are no established criteria for identifying such potential pathogenic areas, particularly when using omnipolar technology (OT) mapping.

Objective

This study aimed to evaluate the correlation between OT and conventional bipolar voltage (BiV) in AF and regular rhythms. Methods Bipolar and OT mapping was performed in 17 patients undergoing de novo ablation for persistent AF. Mapping was performed in AF and coronary sinus pacing (CSP) at 600 ms. BiV of <0.5 mV was defined as low voltage.

Results

LA voltage in AF correlated poorly with CSP using either BiV (r = 0.15) or OT (r = 0.16). OT yielded higher voltages than BiV in AF (0.62 ± 0.24 vs 0.49 ± 0.18 mV, P < .050) and during CSP (1.85 ± 0.78 vs 1.60 ± 0.80 mV, P < .050). LVA burden, as a percentage of LA surface area, varied significantly depending on the atrial rhythm and mapping approach (AF-bipolar 65.0 ± 15.6%, AF-OT 56.2 ± 17.0%, CSP-bipolar 34.2 ± 18.9%, CSP-OT 24.56 ± 13.5%, P < .050). BiV thresholds of 0.5 mV during CSP and 0.3 mV in AF corresponded to an OT voltage of 0.84 mV and 0.40 mV, respectively.

Conclusion

The mapping tool and atrial rhythm significantly influence LA voltage and LVA burden for both bipolar and OT mapping. Applying a universal bipolar or OT cutoff for low voltage in AF and sinus rhythm will not accurately reflect the arrhythmogenic substrate. OT yields higher voltage than corresponding bipolar measurements; thus, threshold adjustments are required when using OT.