Usefulness of pace mapping in catheter ablation of left ventricular papillary muscle ventricular arrhythmias with a preferential conduction.

INTRODUCTION: Preferential conduction from an origin to breakout sites can occur during ventricular arrhythmias (VAs) originating from the left ventricular papillary muscles (LVPMs). The purpose of this study was to investigate the incidence, electrophysiological characteristics, and relevance to radiofrequency catheter ablation (RFCA) of such a preferential conduction demonstrated by pace mapping. METHODS AND
RESULTS: We studied 34 consecutive patients undergoing RFCA of 40 LVPM VAs. Among 78 QRS morphologies during these VAs, pace mapping was performed for 67 QRS morphologies during 37 VAs, and revealed VA-matched pace maps (M-PMs) with a latency for 14 QRS morphologies during 11 VAs (30%). Among 47 QRS morphologies with activation mapping, RFCA at the earliest activation site (EAS) was successful in 39, but not successful in 8 despite M-PMs with no latency. In these cases, RFCA was successful at remote sites of the M-PMs with latency (n = 6) and a site located between the EAS and site of that with latency (n = 1). Among the remaining 31 QRS morphologies with pace mapping only, RFCA was successful at M-PM sites with no latency in 17, and at M-PMs sites with latency in 7. In 3 of those 7 QRS morphologies, M-PMs were recorded at multiple remote sites, and RFCA was not successful at M-PM sites with no latency (n = 2) or a shorter latency (n = 1).
CONCLUSIONS: When an M-PM with latency was recorded in LVPM VAs, RFCA at that site was highly successful. Attention should be paid to latency as well as the score during pace mapping of LVPM VAs.