Unipolar mapping enhances the detection of atrial tachycardias and the prediction of arrhythmia recurrences in AF patients

Background
Low voltage areas (LVAs) in the atrial substrate have gained significance recently, with studies exploring their association with ablation outcomes and potential as ablation targets. While previous research relied on bipolar voltage mapping, recent data highlight the importance of unipolar voltage mapping in evaluating atrial wall scars and detecting structural changes identified in LGE-MRI.

Objective
To investigate the relationship between unipolar and bipolar voltage mapping, arrhythmia recurrence post-ablation (AR), and atrial tachycardia (AT) in patients with atrial fibrillation (AF).

Methods
We conducted a retrospective analysis of 124 patients undergoing repeat ablation after failed pulmonary vein isolation. High-density left atrial maps were obtained. LVAs were quantified using cutoffs of 0.5 mV for bipolar and 2.5 mV for unipolar voltage, aggregated across the atria. We assessed the predictive value of LVAs using feature configurations: unipolar or bipolar only and combined unipolar + bipolar. Additional dispersion metrics between unipolar and bipolar were calculated using relative dispersion and mean-scaled difference. A Random Forest Classifier modeled the relationship between LVAs and the presence of AT and AR after a 15-month follow-up.

Results
In the cohort (59% male, median age 69 years [IQR: 61–76]), 34% remained arrhythmia-free after 15 months. Left atrial maps averaged 4,216 ± 2,230 points. The mean unipolar LVA percentage was 26% ± 13%, and the mean bipolar LVA percentage was 13% ± 10%.

Patients with AR had a significantly higher median unipolar LVA percentage (21.5% [IQR: 11.3–25.7]) compared to those without recurrence (12.7% [IQR: 7.4–21.1], p = 0.031). Although the median bipolar LVA percentage was higher in patients with recurrence (9.1% [IQR: 3.6–15.9]) than in those without (5.8% [IQR: 3.1–8.8]), this difference was not statistically significant (p = 0.137).

In patients with AT, the median bipolar LVA percentage was significantly higher (13.7% [IQR: 7.8–18.4]) than in those without it (5.6% [IQR: 2.9–13.6], p = 0.001). The median unipolar LVA percentage was also higher in these patients (21.5% [IQR: 16.8–25.5] vs. 12.7% [IQR: 8.8–17.3]), but without statistical significance (p = 0.137).

For predicting AR, unipolar LVAs achieved an accuracy of 0.76 (ROC-AUC 0.62); bipolar LVAs had the same accuracy but a lower ROC-AUC of 0.57. Combining unipolar and bipolar LVAs improved accuracy to 0.77 and ROC-AUC to 0.66. Including all features, such as dispersion metrics, further increased accuracy to 0.78 and ROC-AUC to 0.68.

For AT prediction, unipolar LVAs alone yielded an accuracy of 0.81 (ROC-AUC 0.59), while bipolar LVAs alone provided an accuracy of 0.82 (ROC-AUC 0.71). Combining both unipolar and bipolar LVAs enhanced accuracy to 0.83 and ROC-AUC to 0.73. The highest predictive performance was achieved when all features were combined, reaching an accuracy of 0.84 and an ROC-AUC of 0.75.

Conclusion
In patients with AF undergoing repeat ablation procedures, a higher burden of unipolar LVAs was associated with AR. Combining data from both unipolar and bipolar voltage mapping yielded higher predictive values for AR and the presence of ATs compared to using each measurement individually. This suggests that unipolar mapping may provide additional and significant information about the atrial substrate, supporting the incorporation of unipolar mapping alongside traditional bipolar mapping in its assessment.