. Meanwhile, simultaneous recordings of the left atrial appendage were obtained with a catheter positioned in the LAA, and an invasive interatrial conduction time was measured from the origin of the surface's earliest P-wave (I-IACT). The mean I-IACT (46.27 +/- 13.25 ms) correlated strongly with the mean P-LAA (49.91 +/- 12.72 ms; r = 0.839, P<0.0001).