Fig. 1

Analysis of LA-CV. (A) Local triplet points (A, B, and C) were set to make a triad region for measurement of the LA-CV vector along the direction of wave front propagation with avoidance of visual collision in the activation map. When point A was defined as the earliest point in this triangle, vector-AB and vector-AC were calculated for one-dimensional CV with the activation time and distance between points A and B or C. Then, we incorporated cartesian and trigonometric equations to calculate the magnitude of matched components between the vector-AB and vector-AC as forming the orthogonal projection, which resulted in velocity specifically in the two-dimensional direction of activation. (B) Four matched projection vectors were analyzed at different triad regions of each anterior and posterior LA wall. The medians of the LA-CVs from the four triad sites were set as ‘model LA-CVs’ in both anterior and posterior walls. These regions for analysis must be randomly selected and evenly distributed in the whole anterior and posterior regions and not to be inclined toward one side, respectively. CV, conduction velocity; LA, left atrium