Abstract 5683: Mapping of Focal Atrial Tachycardia: The Impact of the Method of Activation Time Determination
Background: Different methods of activation time determination can be used during mapping of focal atrial tachycardia. The present study aimed to compare activation maps generated by 3 widely used methods of activation time determination.
Methods: 14 patients (age 48 ± 17 years) with focal atrial tachycardia were investigated. Mapping was performed with the CARTO system. All patients underwent successful ablation. Local activation time was successively defined as the peak amplitude (Bi-peak), the steepest downslope (Bi-dslope), and the onset (Bi-on) of the bipolar electrograms.
Results: A high-degree correlation existed among the activation times assessed with the 3 methods (correlation coefficient varying between 0.959 and 0.983, p<0.0001). Nevertheless, they generated foci with different spatial locations. Thus, the distance between the focus generated by Bi-peak and that generated by Bi-dslope was 4.32 ± 5.28 mm, the distance between the focus generated by Bi-peak and that generated by Bi-on was 7.37 ± 5.57 mm, and the distance between the focus generated by Bi-dslope and that generated by Bi-on was 4.71 ± 5.72 mm (p=0.18). Also, the 3 methods generated foci with different diameters: 2.61 ± 0.40 mm (Bi-peak), 2.61 ± 0.40 (Bi-dslope), and 6.14 ± 8.07 mm (Bi-on) respectively (p=0.08). Regardless of the method of definition of activation time, the foci were confined to regions of low-amplitude, increased electrogram fractionation. The surface of these regions was 3.81 ± 2.34 cm2 (Bi-peak), 3.38 ± 2.12 cm2 (Bi-dslope), and 4.76 ± 3.01 cm2 (Bi-on) respectively (p=0.34).
Conclusions: The 3 methods of activation time determination, although highly correlated, generate foci of different sizes and with different spatial locations. The foci are however clustered in relatively large areas of low-amplitude, fractionated electrograms. This finding raises the issue of an anatomical substrate of the tachycardia provided by a sizeable atrial region with particular electrophysiological proprieties. During mapping, this region can be roughly delineated by all the 3 methods of activation time estimation. However, details concerning the activation pattern within the region and the location of the earliest activation site vary among the methods.