Prospective comparison of lesions created using a multipolar microcatheter ablation system with those created using a pullback approach with standard radiofrequency ablation in the canine atrium

The aim of this study was to compare the lesions created using a multipolar microcatheter (MICRO) ablation system in the right canine atrium to a pullback approach with a standard radiofrequency (STND RF) ablation and to determine the value of electrogram amplitude and pacing threshold in predicting transmurality of lesions. Ten dogs underwent right atrial ablation using a MICRO (6 dogs) or STND RF (4 dogs) ablation system in each animal. Attempts were made to create linear RF lesions at four predetermined atrial sites. RF energy was delivered for 60 seconds using closed-loop temperature control to achieve a target temperature of 60°C for STND RF and 50°C for MICRO. Unipolar atrial electrogram amplitude and atrial pacing threshold were obtained before and after ablation. Pathological analysis was determined at 4 weeks after ablation. Lesions created with MICRO were narrower, more likely to be continuous, and more likely to be anchored to an anatomic structure than those lesions which were created using a STND RF. No difference was observed in overall lesion length or in the proportion of lesions that were transmural over at least 50% of their length. Of lesions created using MICRO, a significant relation was observed between transmurality of lesion and unipolar electrogram amplitude as well as pacing threshold. Further studies are needed to determine if this type of ablation technique and parameters during ablation may facilitate a successful catheter-based MAZE procedure.