Figure 1. LACV measurement
LACV was calculated by dividing left atrial conduction distance by conduction time. Conduction time was defined as the difference in activation time between the start (septum) and end of the propagation wave front (lateral wall) in the left atrium. Conduction distance was measured manually by tracing the pathway of the propagation wave front from the start point to the end point in the left atrium. The pathways of the propagation wave front were classified into anterior and posterior routes. The anterior route originates at the septum, crosses the anterior wall toward the appendage, passes over the left atrial appendage orifice, and finally reaches the lateral mitral annulus, where superior- and inferior-direction propagation waves collide and disappear. The posterior route goes toward the superior left atrium (roof) from the septal propagation origin, then downward on the posterior wall, turns below the left inferior pulmonary vein, and reaches the lateral mitral annulus. LACV, left atrial conduction velocity; LAT, local activation time.