Post-Infarct Ventricular Tachycardia Substrate: Characterisation and Ablation of Conduction Channels using Ripple Mapping

Abstract Background Conduction channels have been demonstrated within the post-infarct scar and appear to be co-located with the isthmus of ventricular tachycardia (VT). Mapping the local scar potentials (SPs) that define the conduction channels is often hindered by large far-field electrograms generated by healthy myocardium. Objectives We sought to map conduction channel using Ripple Mapping to categorise SPs temporally and anatomically. We tested the hypothesis that ablation of early SPs would eliminate the latest SPs without direct ablation. Methods Ripple maps of post-infarct scar were collected using the Pentaray during normal rhythm. Maps were reviewed in reverse and clusters of SPs color-coded on the geometry, by timing, into early, intermediate, late and terminal. Ablation was delivered sequentially from clusters of early SPs, checking for loss of terminal SPs as the endpoint. Results The protocol was performed in 11pts. Mean mapping time was 65±23min, to collect a mean 3050±1839 points. SP timing ranged from 98.1±60.5ms to 214.8±89.8ms post QRS-peak. Earliest SPs were present at the border, occupying 16.4% of scar, whilst latest SPs occupied 4.8%, at the opposing border or core. Analysis took 15±10 min to locate channels and identify ablation targets. It was possible to eliminate latest SPs in all patients without direct ablation (mean ablation time 16.3 ± 11.1min). No VT recurrence was recorded; mean follow up 10.1 +/- 7.4months. Conclusion Conduction channels can be located using Ripple Mapping to analyse scar potentials. Ablation at channel entrances can eliminate the latest SPs and is associated with good medium-term results.