Left atrial appendage activity translation in the standard 12-lead ECG

Abstract in Undetermined LAA Activity in Surface ECG. Introduction: Interatrial frequency gradient is used to guide catheter ablation of atrial fibrillation (AF). Lead V1 adequately reflects right atrial activity, but reliable tools for noninvasive estimation of right versus left fibrillatory frequency are lacking. In this study, patients with dissociated left and right atrial rhythms were studied in order to identify which surface electrocardiographic (ECG) leads that most closely reflect the left atrial activity. Methods: Two consecutive patients with atrial tachycardia confined to the left atrial appendage (LAA) detected during catheter ablation of AF were included (2 men, 54 and 72 years old). A 12-lead ECG was recorded simultaneously with electrograms from the right and left atrial appendages (RAA/LAA). AF frequency spectra were calculated from all 12 leads using spatiotemporal QRST cancellation and Welch periodogram. The dominating atrial cycle length (DACL) in the surface ECG leads was subsequently compared with the invasively measured LAA cycle length. Results: LAA activation frequency was seen as a prominent peak in the frequency–power spectrum derived from frontal plane leads as well as lead V1. The absolute difference in noninvasively and invasively measured LAA cycle length was lowest for leads aVR, II, aVF, III, and V1 in which it was in the range of 2–4 ms. Conclusion: Prominent left atrial component is present in the majority of standard ECG leads, including those traditionally associated with right atrial activity such as V1. Spectral analysis is able to extract the LAA component on surface ECG