HIGH-DENSITY MAPPING OF ELECTRICALLY-INDUCED ATRIAL-FIBRILLATION IN HUMANS

Background Mapping studies in animals have suggested that atrial fibri llation (AF) is based on multiple reentering wavelets. Little informat ion is available about the patterns of activation during AF in humans. The objective of the present study was to reconstruct and classify th e patterns of human right atrial (RA) activation during electrically i nduced AF. Methods and Results AF was induced by rapid atrial pacing i n 25 patients with Wolff-Parkinson-White syndrome undergoing surgery f or interruption of their accessory pathway(s). The free wall of the RA was mapped using a spoon-shaped electrode containing 244 unipolar ele ctrodes. The activation of the RA during AF showed large interindividu al differences. Based on the complexity of atrial activation, three ty pes of AF were defined. In type I (40% of patients), single broad wave fronts propagated uniformly across the RA. Type II (32%) was characte rized by one or two nonuniformly conducting wavelets, whereas in type III (28%), activation of the RA was highly fragmented and showed three or more different wavelets that frequently changed their direction of propagation as a result of numerous arcs of functional conduction blo ck. There were significant differences (P<.05) among the three types o f AF in median intervals (174+/-28, 150+/-14, and 136+/-16 millisecond s), variation in AF intervals (P-5-95) (54+/-25, 94+/-21, and 104+/-22 milliseconds), incidence of electrical inactivity (42+/-11%, 21+/-4%, and 8+/-4%) and reentry (3+/-7%, 36+/-28%, and 99+/-36%), and average conduction velocity during AF (61+/-6, 54+/-4, and 38+/-10 cm/s). Con clusions During pacing-induced AF in humans, the RA is activated by on e or multiple wavelets propagating in different directions. Three type s of RA activation during AF were identified. From type I to type III, the frequency and irregularity of AF increased, and the incidence of continuous electrical activity and reentry became higher. These variou s types of AF in humans appear to be characterized by different number s and dimensions of the intra-atrial reentrant circuits.