QUANTITATIVE ASSESSMENT OF THE SPATIAL-ORGANIZATION OF ATRIAL-FIBRILLATION IN THE INTACT HUMAN HEART

Background Atrial activation during atrjal fibrillation (AF) is freque ntly described as random or chaotic. We propose that activation during AF is constrained by the principles of reentrant excitation; that the se constraints impart a measurable spatial organization to activation during AF; and that the distance over which activation sequences remai n well correlated can be readily measured and related both to the prop ensity of AF to sustain itself as well as to atrial tissue wavelength. Methods and Results We describe a novel signal-processing technique t hat quantifies the correlation in activation sequences recorded from f ive equally spaced sites in the right atrium in patients undergoing el ectrophysiology studies. In 20 patients in AF (12 with paroxysmal AF, 5 with chronic AF, and 3 withno clinical history of AF), the average c orrelation was 0.54+/-0.12 at 11 mm and 0.32+/-0.11 at 44 mm, compared with 0.95+/-.023 and 0.91+/-.023 in sinus rhythm. In AF, the correla tion versus distance relation was monotonically decreasing, well fit b y a decaying exponential function. The space constant of this exponent ial function, termed the activation space constant, provides a single objective metric of the spatial organization of activation during AF. The mean activation space constant for the group was 2.6+/-1.15 cm. Ch ronic AF had the lowest mean activation space constant (1.84+/-0.36 cm ) and AF in patients with no prior history of AF had the highest (3.06 +/-0.40 cm) (P<.05), with paroxysmal AF characterized by intermediate values (2.80+/-1.4 cm). Conclusions Using a novel method to measure th e spatial organization of atrial activation during AF, we have demonst rated that AF in the intact human heart is organized over a length sca le consistent with reentrant excitation. Preliminary results suggest a relationship between measured spatial organization and the clinical c ourse of the arrhythmia. Further work is needed to determine whether m easurement of spatial organization may be useful in prospective patien t-specific selection of therapeutic options.