Segregating non-isthmus dependent atrial flutter from organized atrial fibrillation using spectral and spatial phase analysis of the electrocardiogram

Distinguishing atrial flutter (AFL) from ´organized´ atrial fibrillation (AF) from the ECG is important for optimal therapy, yet remains difficult. We hypothesized that analyzing the temporal and spatial regularity (phase) of ECG F-waves would separate AFL, even with F-wave variability, from AF. We studied ECGs in patients with isthmus (IDAFL; n = 19) and non-isthmus (NIDAFL; n = 11) dependent AFL, and AF (n=7). ECG atrial activity in AFL, represented as correlations of a template to successive ECG timepoints, showed a dominant spectral peak at a frequency corresponding to the measured atrial cycle length; no distinct spectral peak was seen in AF. F-wave spatial vector, measured as the relationship of atrial correlations between axes, was more consistent in IDAFL than NIDAFL, and inconsistent in AF. Temporal and spatial phase therefore separate NIDAFL with variable F-waves from AF, and from IDAFL. This technique may help to guide the approach to ablation.