Ventricular substrate characterization using high-density omnipolar mapping in patients with repaired tetralogy of fallot

Background High-density electroanatomical mapping enables the characterization of the arrhythmic substrate in patients with repaired Tetralogy of Fallot (rTOF), facilitating the identification and ablation of slow-conducting anatomical isthmuses (SCAIs) responsible for ventricular tachycardia. It is unknown whether the use of omnipolar mapping (OM) technology provides a more accurate characterization of the arrhythmic substrate in this setting. Purpose To investigate the differences between voltage maps and isochronal late activation mapping (ILAM) derived from bipolar and omnipolar signals, and to assess the correlation between voltage values obtained by each method in patients with rTOF. Methods Electroanatomical maps from 12 patients with rTOF were analysed using omnipolar mapping, from which corresponding bipolar maps were derived. Omnipolar and bipolar voltages were compared, as well as the automated last-deflection annotation error. Differences in the areas of anatomical isthmuses obtained with each mapping modality were evaluated. Results OM identified significantly higher median global voltages (0.99 mV [0.42–2.91] vs 0.57 mV [0.26–1.43], p < 0.01). The area of abnormal voltage was significantly smaller with OM (64.51 cm² [50.86–52.45] vs 79.43 cm² [54.48–95.13], p = 0.012), with a relative voltage difference of 12.9% (53.7% by OM and 64.05% by bipolar mapping). OM showed higher point density (20.06 points/cm² [12.68–23.19] vs 15.20 points/cm² [12.75–19.26], p < 0.01). Last-deflection annotation was more accurate with OM, with a lower ILAM algorithm automatic error rate (6.6 ± 7 vs 16.6 ± 9; paired-samples W: 3.0, p = 0.01). Seven SCAI areas were measured, with OM showing a smaller area compared with bipolar (2.65 cm² [1.65–3.8] vs. 4.4 cm² [2.4–5.2]), with no statistically significant difference (p = 0.18). Conclusion OM demonstrated significantly higher voltage values and a smaller area of abnormal voltage, and the area of the SCAIs in OM showed a non-significant trend towards a smaller size. Omnipolar ILAM annotation was significantly more accurate than conventional bipolar mapping.