Electrically unexcitable scar mapping based on pacing threshold for identification of the reentry circuit isthmus: feasibility for guiding XXXX .

@entity1 @entity1188 @entity1165
BACKGROUND: We hypothesized that delineating electrically unexcitable scar (EUS) within low-voltage @entity1188 regions will locate reentry circuit isthmuses by defining their borders. The pacing threshold and electrogram amplitude that best determines EUS is unknown. METHODS AND RESULTS: The change in dimension of the virtual electrode was estimated in 11 @entity1 and observed to increase by 4.4+/-2.5 mm as stimulus strength increases from threshold (2.9+/-1.8 mA) to 10 mA. EUS was defined as a threshold >10 mA. In 14 consecutive @entity1 , mapping and ablation of @entity1165 ( @entity1165 ) were performed using an electroanatomic mapping system. During sinus rhythm, unipolar pacing was performed at sites with bipolar electrogram amplitude <1.5 mV. EUS regions were marked on the maps. Reentry circuit isthmuses were identified by entrainment mapping or pace mapping, and ablation was performed. EUS was identified in the @entity1188 in all 14 @entity1 (11.8+/-13.9 cm2). All 20 @entity1165 circuit isthmuses identified were adjacent to EUS. Although electrogram amplitude correlated with pacing threshold (r=0.64, P<0.0001), many isthmuses had very low-amplitude electrograms, and EUS could not be identified from electrogram amplitude alone. RF ablation lines connecting selected EUS regions abolished all inducible VTs in 10 @entity1 (71%); spontaneous @entity1165 was markedly reduced during follow-up (from 142+/-360 to 0.9+/-2.0 episodes per month, P=0.002). CONCLUSIONS: This new method of identifying EUS provides complimentary information to the electrogram amplitude in delineating potential reentry circuit paths, potentially facilitating ablation during sinus rhythm.
