The distribution of local activation directions during human atrial fibrillation: implications for linking

In this study, the authors examine how the perception of linking during atrial fibrillation (AF) depends on the choice of threshold angle for defining linking. AF recordings were made using an orthogonal catheter, and the direction of each activation was calculated. Threshold angle was varied from 0 to 180 degrees. For each value, pairs of adjacent activations with directions differing by an angle no greater than the threshold were identified; consecutive strings of 5 or more such pairs were defined as one episode of linking. Plots of percentage of electrograms defined as linked vs. threshold angle were made for each recording, and compared with similar plots for sinus rhythm and random vectors. The results indicate that local activation during AF is different from random activation. However, no optimal threshold angle for defining linking could be identified