EFFECT OF ELECTROPHYSIOLOGIC PROPERTIES AND LOCATION OF MANIFEST ACCESSORY PATHWAYS ON LOCAL ELECTROGRAM INTERVALS AT EFFECTIVE RADIOFREQUENCY ABLATION SITES

The purpose of this study was to determine if the electrophysiologic p roperties and the anatomic location of manifest accessory pathways aff ect the local electrogram intervals recorded at sites of successful ra diofrequency ablation. Accessory pathways in 149 consecutive patients were categorized according to their anatomic location on the basis of the site of successful ablation. Three anatomic groups comprised 90 le ft free wall, 28 right free wall, and 31 posteroseptal pathways. The a ccessory pathways were also categorized according to their electrophys iologic properties on the basis of a hierarchical classification of th e accessory pathway block cycle length. Four electrophysiologic groups (A, B, C, and D) comprised 54, 51, 28, and 16 accessory pathways, wit h mean accessory pathway block cycle lengths of 254 +/- 9, 288 +/- 10, 347 +/- 19, and 458 +/- 56 msec, respectively. The local atrial to ve ntricular (A-V) and atrial to accessory (A-K) pathway electrogram inte rvals recorded in sinus rhythm at the successful ablation site were si gnificantly affected by the electrophysiologic group and were longest in group D compared with groups A, B, and C (A-V interval F-(3,F-145) = 13.6 p < 0.001; A-K interval F-(3,F-88) = 12.6, p < 0.001). The loca l A-V interval was also affected by the anatomic group and was longer in posteroseptal compared with free wall accessory pathways (F-(2,F-14 6) = 75.0, p < 0.001). In contrast, the timing of the local ventricula r activation to the delta wave onset (delta-V) was not significantly a ffected by the electrophysiologic group or the anatomic location of th e accessory pathway. Thus the local A-V interval at the successful abl ation site may vary because it is affected by the electrophysiologic p roperties and location of the accessory pathway, whereas the delta-V i nterval remains unaffected. These effects should be taken into account when selecting ablation sites in patients with manifest accessory pat hways.