3.5. LACV measurement
Left atrial conduction distance and conduction time were calculated from
the start to the end of the propagation wave front in the left atrium.
LACV was calculated as conduction distance divided by conduction time.
An example LACV measurement is presented in Figure 1. Conduction time
was 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 goes downward on
the posterior wall, turns below the left inferior pulmonary vein, and
reaches the lateral mitral annulus.
Reproducibility of the LACV was assessed. Interobserver variability for
anterior and posterior LACV was 0.025 m/s, calculated in 10 randomly
selected patients as the difference in 2 measurements in the same
patient by 2 different observers. There was no difference in anterior
(0.88 [0.81, 1.06] vs. 0.88 [0.80, 1.06] p=0.86) or posterior
LACV values (1.08 [0.86, 1.23] vs. 1.07 [0.85, 1.23], p = 0.55)
between 2 examiners.