Differences Between the Unipolar Versus Bipolar Potential-Based Activation Maps of Ventricular Premature Contractions Arising From Ventricular Outflow Tracts.

Background: The use of an automated annotation algorithm based on the maximal negative derivative of the unipolar potential (-dV/dTmax) for local activation timing in the ablation of outflow tract (OT) ventricular premature contractions (VPCs) remains controversial.

Objective: To investigate the spatial differences in the earliest activation sites (EASs) of OT-VPCs identified by an automated annotation based on unipolar -dV/dTmax versus manual annotation using local bipolar potentials.

Methods: Seventy-nine patients with frequent OT-VPCs who underwent successful ablation were included. VPCs originated from the right ventricular OT (RVOT) free wall (n = 10), RVOT septum (n = 25), aortomitral continuity (AMC) (n = 19), and aortic sinus cusps (ASCs) (n = 25). The spatial distance between EASs identified by the two annotation methods was analyzed.

Results: The spatial distance between EASs was significantly larger in ASC-origin VPCs compared to non-ASC-origin VPCs (median: 11.9 mm [IQR: 7.9-14.9] vs. 1.2 mm [IQR: 0.0-3.3], p < 0.001). Among non-ASC-origin VPCs, the spatial difference was smallest in VPCs from the RVOT free wall (median: 0 mm) and larger in those from the RVOT septum (median: 1.6 mm) and AMC (median: 2.2 mm).

Conclusion: The spatial discordance of EAS between unipolar and bipolar mapping varies by the VPC origin site. The discrepancy is particularly pronounced in ASC-origin VPCs, emphasizing the need for careful interpretation of automated annotation algorithms to ensure accurate localization and effective ablation.