Left Atrial P-Wave Analysis and Corresponding Invasively Measured Left Atrial Activation Time in a Patient Without Relevant Low-Voltage Substrate
(A) Twelve-lead surface electrocardiogram of a representative patient with absence of low voltage. Left atrial P-wave duration (LAP) is measured from the point of highest negative deflection (−dV/dt max) in lead V1 or V2 to the end of the P-wave in any of the leads (here 68 ms). Total P-wave duration is measured from the earliest deflection in any lead to the last point of electric activity in any lead (here 128 ms). Voltage map of the same patient at 1.0-mV cutoff shows no significant low-voltage areas in the anterior (B) and posterior (C) views. (D, E) Activation mapping of this patient demonstrates fast activation that spreads from the septum to the left atrial appendage (65 ms). The earliest activation of the septal left atrium as demonstrated in the activation map (red area in D) corresponds to −dV/dt max in lead V1 or V2(F, orange arrows). LAT = left atrial activation time.