SPATIAL-RESOLUTION AND ROLE OF PACEMAPPING DURING ABLATION OF ACCESSORY PATHWAYS

The objectives of this study were: (1) to evaluate quantitatively the spatial resolution of pacemapping; and (2) to assess the predictive va lue and role of pacemapping for the catheter ablation of overt APs. Si xty-three unipolar leads were used instead of the standard 12-lead ECC to acquire more information and assess the intrinsic accuracy of pace mapping. Spatial resolution was evaluated in 19 patients for whom 1 da ta were recorded during bipolar ventricular pacing near the AV ring us ing the three electrode pairs of a quadripolar ablation catheter with a 5-mm interelectrode spacing. The predictive value was assessed in 27 patients with overt APs who underwent RF ablation; their data were re corded during pacing at the site of successful ablation and at one or two sites where RF energy delivery was ineffective. Data from differen t beats were compared visually by using body surface potential maps an d quantitatively by computing average correlation coefficients (r). Re producibility was high for paced beats (r = 0.98 +/- 0.02). Displaceme nts of 5 mm of the pacing site could be detected with a sensitivity of 90% and a specificity of 87%. Correlation between pacing at successfu l ablation sites and preexcited sinus rhythm was low (r = 0.79 +/- 0.1 1) and the ablation outcome could be predicted with a negative predict ion accuracy of 87% and a positive prediction accuracy of 49%. Despite an excellent spatial resolution, pacemapping is of limited value for the identification of successful AP ablation sites, probably because A Ps can be interrupted at some distance from their ventricular insertio n point.