Voltage and propagation mapping: new tools to improve successful ablation of atrioventricular nodal reentry tachycardia

Abstract Funding Acknowledgements Type of funding sources: None. Background Ablation of atrioventricular nodal reentry tachycardia (AVNRT) has become the treatment of choice for AVNRT due to high success and low complication rate. A 3-D reconstruction of the atrial endocardial anatomy created by mapping system is useful because anatomic variances or unusual slow pathway locations may affect the effectiveness of classical anatomical approach. Voltage mapping is useful to identify a low voltage area in the Koch triangle (KT) called low-voltage-bridge (LVB); propagation mapping identifies the collision point (CP) of atrial wavefront convergence. These technique may be helpful to improve the localization of the slow pathway. Purpose Our purpose is to conduct a prospective study to evaluate the relationship of the propagation map to voltage mapping and successful site of ablation; moreover we would identify a cut-off value of LVB able to standardized the procedure. Methods Voltage maps of KT (at least 150 points) were obtained through the ablation catheter. Voltage values were adjusted until LVB was observed and classified in two types (Pic 1): Type I is a clear, large area; Type II is a narrow corridor or small areas. The collision point is the area in which the atrial wavefront during sinus rhythm collided on the propagation map indicating the area of slow pathway conduction. Ablation site was selected by LVB position or collision point, confirmed on anatomic position or AV ratio. Ablation of the slow pathway was performed using radio-frequency (RF) or cryotherapy. Results Eighteen consecutive patients were included; one patient was excluded because of inadequate voltage map. Ten patients were female. The median age was 51. In all patients inducible typical AVNRT was present. In 8 patients RF energy was used. Mean procedure time was 109 minutes; mean fluoroscopy time was 3,4 seconds (zero-fluoro procedure in 13 patients). Procedure success (no inducible AVNRT and no more than a single AV node echo beat) was achieved in all patient. No procedural complications were observed. No recurrence at 1 year follow up. The LVB was present in all patients; 9 patients had a type 1 LVB. Voltage map was created adjusting voltage high and low ranges in order to visualize LVB. Limited of LVB visualization is the leak of standard range of value for map creation. Post procedural evaluation identified standard cut-off of 0.3-1mv useful for LVB identification (only one patient had lower voltage range). The collision point was present in all patients. A correlation between LVB and CP was observed in 17/18 patients (Pic 2). In 16 patients successful ablation site was within 5mm of the wave collision. Conclusion In our prospective study, we found correlation between LVB and CP and the site of effective slow pathway ablation in most patients, and we identified a voltage range useful for standardized LVB identification during voltage mapping. Moreover, these techniques are useful to identify ablation site and minimize radiation exposure.