901-61 Localization of the Return Pathway in Ischemic Ventricular Tachycardia by Diastolic Potential Mapping

Successful treatment of ischemic VT, including by catheter ablation, requires accurate interpretation of the local electrograms. Diastolic potentials may be recorded over a wide area of the endocardium. This study investigated the relationship of the return pathway in VT to the area displaying diastolic activity. 78 VTs in 30 patients were mapped endocardially at time of surgery. Complete return pathways were seen in 17 VTs of 10 patients. The return pathway was defined by tracking diastolic potentials from the earliest diastolic signal towards the site of VT origin. Conduction time over the return pathway represented the diastolic interval. The area of diastolic activity was determined by calculating the area enclosed by electrodes showing diastolic potentials from an inflated endocardial balloon.ResultThe mean return pathway conduction time was 90±31 ms (range 40-140 ms). Mean diastolic interval was 64±23 ms Irange 30-115 ms). The mean area over which diastolic activity could be seen was 317±255 mm2(range 28-920 mm2). In all 17 VTs, diastolic activity was seen within 15 mm of site of origin, and this represented an area of 98±65 mm2(range 28-170 mm2). 62% local electrograms within 15 mm of site of origin showed a diastolic potential to QRS interval<70 ms. All patients with such a pattern were cured by surgery, but 2 of 4 patients with diastolic potential to QRS interval≥70 ms had VT recurrence. VT cycle length correlated with the conduction time of return pathway (R=0.765, p=0.0002), but not with the area of the return pathway.Implication1) Region exhibiting diastolic potentials was far greater than the return pathway per se. 2) Characterization of the timing of diastolic potentials relative to the QRS complex helps to identify critical portions of the return pathway close to the VT site of origin. 3) Such analysis may differentiate critical areas of the return pathway from bystander regions. 4) These observations may help direct radio-frequency ablation in the catheter laboratory