Non-invasive assessment of direction of right atrial activation during atrial fibrillation using correlation function analysis

ECGs were recorded from three electrodes attached at the corners of an equilateral triangle positioned around the location of electrode V1. The atrial signal between QRST complexes was subjected to correlation function analysis to reveal differences in activation times between the electrode sites. The time differences found were used to calculate the direction of activation across the body surface. Twenty-three subjects were studied during sinus rhythm (SR), intraoperatively confirmed typical and reverse typical atrial flutter, or during paroxysmal or permanent atrial fibrillation (AF). Subjects studied during SR and patients with typical atrial flutter exhibited a uniform direction of activation, with the main vector pointing downwards. The propagation of atrial activation during permanent AF did not show a consistent direction, while patients with paroxysmal AF exhibited more uniform activation vectors, corresponding to the direction observed in patients with atrial flutter.