Impact of heart rhythm status on registration accuracy of the left atrium for catheter ablation of atrial fibrillation.

INTRODUCTION: Registration accuracy is of crucial importance to the successful use of image integration technique to facilitate atrial fibrillation (AF) ablation. It is well known that a patient's heart rhythm can switch from sinus rhythm (SR) to AF or vice versa during an AF ablation procedure. However, the impact of the heart rhythm change on the accuracy of left atrium (LA) registration has not been studied.
METHODS: This study included 10 patients who underwent AF ablation. Prior to the ablation procedure, the patients had contrast-enhanced cardiac CT scan obtained during SR (n = 7) or AF (n = 3). Using an image integration system (CartoMerge, Biosense Webster Inc.), LA CT surface reconstruction was registered to the real-time mapping space represented by the LA electroanatomic map. To determine the effect of rhythm change on registration accuracy, LA registration was performed during both SR and AF in each study subject. The distance between the surface of the registered LA CT reconstruction and multiple real-time LA electroanatomic map points (surface-to-point distance) was used as an index for LA registration error. The position error after rhythm change was defined as the surface-to-point distance between the surface of the LA CT reconstruction registered in the initial rhythm and the LA electroanatomic map points sampled during the second rhythm.
RESULTS: A total of 90 +/- 12 and 92 +/- 9.5 LA electroanatomic map points were sampled for registration during SR and AF, respectively. No significant difference was found in surface-to-point distance when comparing SR with AF as the underlying rhythm during registration (1.91 +/- 0.24 vs 1.84 +/- 0.38 mm, P = 0.60). The position error after rhythm change was not different from the surface-to-point distance of LA registration conducted during the initial rhythm (2.05 +/- 0.39 vs 1.96 +/- 0.29 mm, P = 0.4). The surface-to-point distance did not differ when comparing LA registration conducted during the same versus different rhythm from that during CT imaging (1.96 +/- 0.29 vs 1.79 +/- 0.32 mm, P = 0.13).
CONCLUSIONS: Registration error did not differ between LA registrations conducted during the same versus different rhythm as was present during CT imaging. Rhythm changes between SR and AF did not introduce significant error to the LA registration process for catheter ablation of AF. These findings are reassuring and suggest that reregistration is not needed if a patient's rhythm changes from SR to AF or vice versa during an ablation procedure.