Delineation of the patterns of activation of the human left atrium during sinus rhythm using a non-contact mapping system

The pattern of left atrial (LA) activation during sinus rhythm (SR) in humans has not been delineated. The authors used a non-contact mapping system to analyze the patterns of left atrial (LA) activation during sinus rhythm and pacing. The system is capable of simultaneously reproducing more than 3,000 electrograms, which are superimposed on a virtual left atrial endocardium. Data were recorded in sinus rhythm and during pacing from the high right atrium, coronary sinus os, and right atrial septum. The authors demonstrate that during sinus rhythm, the LA activates mainly through posterior septal fibers, adjacent to the ostia of the right pulmonary veins. This suggests that, in humans, anterior interatrial connections including Bachmann´s bundle may be less important than previously recognized