Improved detection of accessory pathways that bridge posterior septal and left posterior regions in the Wolff-Parkinson-White syndrome.

To improve the detection of accessory pathways that bridge the posterior septum and left posterior free wall, catheter maps of the coronary sinus from 21 patients (group I) who needed dissection of both these anatomic regions were compared with data from 23 (group II) with pathways confined to the posterior septum and from 9 (group III) with left posterior pathways. A decapolar catheter was used to map the coronary sinus in 0.5 to 1 cm steps. Intraoperative mapping was performed with a 16-electrode band. Catheter maps during atrial pacing and orthodromic supraventricular tachycardia were analyzed for the site of earliest activation and for differences in a new directional measure of conduction time between adjacent mapping sites. The site of earliest activation alone did not distinguish accessory pathways that bridged both anatomic regions, because 14 of 21 patients (66%) in group I would have been misclassified to either group II or III. In contrast, anterograde and retrograde directional conduction times distinguished patients in group I from those in groups II (p less than 0.01 to less than 0.0003) and III (p less than 0.04 to less than 0.0001). A multivariate model that incorporated the observed differences in directional interelectrode conduction times improved the identification of group I patients, with a sensitivity of 87% and a specificity of 90%. The results define new features in activation patterns measurable during catheter mapping that identify accessory pathways that bridge the posterior septum and left posterior free wall.