HETEROGENEITY OF RETROGRADE FAST-PATHWAY CONDUCTION PATTERN IN PATIENTS WITH ATRIOVENTRICULAR NODAL REENTRY TACHYCARDIA - OBSERVATIONS BY USE OF SIMULTANEOUS MULTISITE CATHETER MAPPING OF KOCHS TRIANGLE

Background Selective ablation of either the fast or the slow pathway r esulting in cure of AV nodal reentry tachycardia (AVNRT) has led to th e concept that these pathways are discrete, anatomically defined struc tures. We hypothesized that if a discrete retrograde fast pathway exis ts, it should be possible to record a single focus of early atrial act ivation near the apex of Koch's triangle, with sequential spread of de polarization to the rest of the atria. Methods and Results We evaluate d 46 patients (33 women, 13 men; mean age, 45+/-43 years) undergoing e lectrophysiology study and catheter ablation for typical AVNRT. Retrog rade atrial activation during AVNRT (337+/-43 ms) and ventricular paci ng at a similar cycle length (352+/-51 ms) was recorded in the region of Koch's triangle with a decapolar catheter in the His bundle positio n, a multipolar catheter in the coronary sinus, and a deflectable quad ripolar catheter along the tricuspid annulus anterior to the coronary sinus ostium. Earliest atrial activation was recorded at the apex oil the triangle of Koch in 38 patients during ventricular pacing and in 4 3 patients during AVNRT. A broad wave front of atrial activation was r ecorded in 17 patients during ventricular pacing and in 26 patients du ring AVNRT. During AVNRT, only 2 patients had a single early site with focal and sequential activation along the tendon of Todaro, There was concordance in the pattern of atrial activation between ventricular p acing and AVNRT in only 21 of 46 patients. Conclusions Retrograde atri al activation over the fast pathway is heterogeneous within Koch's tri angle and the coronary sinus, both for the entire population and for i ndividual patients during different modes of activation. These data do not support the concept of an anatomically discrete retrograde fast p athway.