Direct visualization of the slow pathway using voltage gradient mapping: a novel approach for successful ablation of atrioventricular nodal reentry tachycardia

Aims Ablation of atrioventricular nodal reentry tachycardia (AVNRT) has become treatment of choice because of a high success and low complication rate. Most ablations are successful in utilizing an anatomic approach, but anatomic variance, unusual pathway locations, or multiple pathways may complicate the procedure. Visualization of the slow pathway could expedite ablation success and enhance safety. Our purpose is to determine whether voltage gradient mapping can directly image the slow pathway and aid successful ablation of AVNRT. Methods and results Three-dimensional voltage maps of the right atrial septum were constructed from intracardiac recordings obtained by contact mapping. Voltage values were adjusted until low-voltage bridging was observed within the Triangle of Koch. Forty-eight consecutive patients undergoing ablation for inducible AVNRT, underwent voltage gradient mapping. The slow pathway was identified in all 48 patients via its corresponding low-voltage bridge. Ablation of the slow pathway associated low-voltage bridges in 48 patients was successful in preventing reinduction following the first lesion in 43 of 48 patients. Five patients had multiple slow pathways and >1 lesion was required to prevent reinduction. Repeat mapping confirmed the absence of low-voltage connections previously observed in all 48 patients. Conclusion Voltage gradient mapping can assist in visualization of the slow pathway. Ablation of the associated low-voltage bridge results in loss of slow pathway function and significant changes in the post-ablation voltage map. We conclude that voltage gradient mapping offers the ability to target the slow pathway for successful ablation.