title: Quantifying intracardiac organization of atrial arrhythmias using temporospatial phase of the electrocardiogram.
abstract: BACKGROUND
  Separating nonisthmus-dependent atrial flutter (AFL) from "organized" atrial fibrillation (AF), or isthmus-dependent AFL, may be difficult using ECG characteristics alone. We hypothesized that temporal and spatial phase analysis of ECG atrial waveforms could effectively separate these rhythms by quantifying subtle variations in ECG atrial activation during supraventricular tachycardias (SVT).
  
  
  RESULTS
  We studied 52 patients at electrophysiologic study (EPS) who demonstrated isthmus-dependent (n = 15) and nonisthmus-dependent (n = 9) AFL, atrial tachycardia (n = 6), AV nodal reentry (n = 9), orthodromic reciprocating tachycardia (n = 6), and AF (n = 7). Atrial activity was represented as a series of correlations of an atrial template to successive time samples of the arrhythmia ECG. Spatial phase was analyzed as a reproducible relationship of this atrial activity between leads over time; temporal regularity was measured from power spectra. Spatial phase was maintained (coherent) in lead planes V5/aVF (XY), V5/V1 (XZ), and aVF/V1 (YZ) in 15 of 15 cases of isthmus-dependent AFL, but in only 1 of 9 cases of nonisthmus-dependent AFL (P < 0.01; chi2). Temporally, all cases of AFL showed one dominant peak on correlation spectra (magnitude >6 dB), suggesting one activation wavefront, although this was smeared in nonisthmus-dependent cases. In contrast, AF showed inconsistent spatial phase in all planes and broad band spectra, consistent with multiple and/or variable activation paths. All other SVTs showed spatial coherence and one dominant spectral peak.
  
  
  CONCLUSIONS
  Coherence of temporal and spatial phase is a powerful approach to measure the spatial organization of intracardiac activation from the ECG that reveals a spectrum from SVT to isthmus-dependent and nonisthmus-dependent AFL, to AF.
authors.affiliation: Division of Cardiology, Department of Medicine, University of California-San Diego and Veterans Administration Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161, USA. snarayan@ucsd.edu
authors.forename: Sanjiv M
authors.initials: SM
authors.lastname: Narayan
authors.forename: Gregory K
authors.initials: GK
authors.lastname: Feld
authors.forename: Alborz
authors.initials: A
authors.lastname: Hassankhani
authors.forename: Valmik
authors.initials: V
authors.lastname: Bhargava
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001281:Atrial Fibrillation / Q000503:physiopathology; D001282:Atrial Flutter / Q000503:physiopathology; D016275:Atrial Function; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D015203:Reproducibility of Results; D013617:Tachycardia, Supraventricular / Q000503:physiopathology