Localizing circuits of atrial macroreentry using electrocardiographic planes of coherent atrial activation.

BACKGROUND: The complexity of ablation for atrial macroreentry atrial flutter (AFL) varies significantly depending on the circuit location. Presently, surface electrocardiogram (ECG) analysis poorly separates left from right atypical AFL and from some cases of typical AFL, which delays diagnosis until invasive study.

OBJECTIVE: The purpose of this study was to differentiate and localize the intra-atrial circuits of left atypical AFL, right atypical, and typical AFL using quantitative ECG analysis.

METHODS: We studied 66 patients (54 men, age 59 +/- 14 years) with typical (n = 35), reverse typical (n = 4), and atypical (n = 27) AFL. For each, we generated filtered atrial waveforms from ECG leads V5 (X-axis), aVF (Y-axis), and V1 (Z-axis) by correlating a 120-ms F-wave sample to successive ECG regions. Atrial spatial loops were plotted for three orthogonal planes (frontal, XY = V5/aVF; sagittal, YZ = aVF/V1; axial, XZ = V5/V1) and then cross-correlated to measure spatial regularity (i.e., coherence; range -1 to 1).

RESULTS: Mean coherence was greatest in the XY plane (P <10(-3) vs. XZ or YZ). Atypical AFL showed lower coherence than typical AFL in the XY (P <10(-3)), YZ (P <10(-6)), and XZ (P <10(-5)) planes. Atypical left AFL could be separated from atypical right AFL by lower XY coherence (P = .02); for this plane, coherence <0.69 detected atypical left AFL with 84% specificity and 75% sensitivity. F-wave amplitude alone did not separate typical, atypical right, or atypical left AFL (P = NS).

CONCLUSIONS: Atypical AFL shows lower spatial coherence than typical AFL, particularly in the sagittal and axial planes. Coherence in the Cartesian frontal plane separated left and right atypical AFL. Such analyses may be used to plan ablation strategy from the bedside.