Geometrically accurate activation mapping of the atrioventricular node region during surgery

A novel method has been developed to map activation in the triangle of Koch during surgery for cardiac arrhythmias and relate the map to anatomic landmarks. It uses a hand-held electrode mounted in a freely moving linkage that has three degrees of mechanical freedom. The movements of the linkage are sensed by a computer that continuously calculates the coordinates of the electrode. The surgeon clamps the device over the triangle of Koch after the right atrium has been opened and uses the electrode to trace the anatomic landmarks of the region that are displayed on the computer screen. The position of the electrode is displayed continuously relative to these landmarks and electrograms are recorded at known positions to generate a map. The activation sequences during sinus rhythm, atrioventricular node reentrant tachycardia, "common" and "uncommon" atrial flutter, long RP' tachycardia and retrograde conduction through paranodal pathways are presented. It is concluded that 1) the high spatial resolution reveals physiologically important areas in the maps that are 8 mm long and 3 mm wide and that these areas can be related to specific anatomic landmarks; 2) there are complex electrograms in the region that may reflect the activation of different myocardial layers; and 3) there are marked changes in conduction velocity and direction within the region.