F-wave amplitude stability on multiple electrocardiogram leads in atrial fibrillation

Fibrillatory wave (f-wave) amplitude correlates with left atrium (LA) size in certain electrocardiogram (ECG) leads and it is regarded as a predictor of ablation therapy outcome for atrial fibrillation (AF). This study aims at assessing the temporal stability of f-wave amplitude measures throughout the recording and determining the minimum signal length necessary to characterize them accurately in ECG leads. In a set of standard ECGs acquired in 34 persistent AF patients, we determined the minimum temporal window length W such that the related amplitude value accurately correlated with that from the whole atrial activity (AA) signal in leads I, II, V₁-V₆ (threshold Pearson´s correlation coefficient R = 0.9). Subsequently, we tested intrarecording correlation between amplitude values obtained in two distinct W -second AA signal excerpts. This procedure was performed both on the original AA signal and on its principal component analysis (PCA) rank-1 approximation. The first experimental step yielded W = 5 seconds. Amplitude intrarecording correlation was generally accurate in all leads for W = 5 seconds (R_min = 0.799, V₁; R_max = 0.999, V₃). Interestingly, PCA revealed that amplitude measures are more stable in proximity to LA (R(V₁) = 0.975; R(V₂) = 0.993; R(V₃) = 0.989). Our findings confirm the temporal stability off-wave amplitude measures and their robustness to signal duration. Moreover, a preprocessing stage based on PCA improves the stability of this parameter in leads closer to LA.