Automated rhythm-based control of radiofrequency ablation close to the atrioventricular node: pre-clinical, animal and first-in-human testing.

Background Risk of heart block during radiofrequency ablation of AVNRT and septal accessory pathways is minimized by rapidly ceasing ablation in response to markers of risk, such as atrio-ventricular dissociation, fast junctional rhythm, PR interval prolongation, or two consecutive atrial or ventricular depolarisations. Currently this is done manually. Objective To build and test a control system able to monitor cardiac rhythm and automatically terminate ablation energy when required. Methods The device was built from off-shelf componentry. Pre-clinical testing involved real-time input of EGM/ECG data from 209 ablations (20 patients) over slow (n=19) and fast (n=1) AV nodal pathways. Device response speed was compared to human response. The device's ability to prevent heart block was tested in 5 sheep. First-in-human testing was then performed in 12 patients undergoing AVNRT ablation. Results Risk conditions necessitating shut-off of ablation (200 total; 111 pre-clinical, 89 first-in-human) were detected by the device with 100% sensitivity, and 94% specificity, automatically terminating ablation while still allowing successful ablation in all patients. Device shut-off of ablation was always faster than human response (median difference 1.24s). In each of five sheep, 40 consecutive attempts to cause heart block by ablating over the His bundle were unsuccessful due to automatic shut-off in response to rhythm change. Conclusions Automated shut-off of ablation close to the AV node in response to markers of risk for heart block is feasible with high accuracy, and faster response than human. The system may increase safety of ablation near the AV node by preventing heart block.