PT  - JOURNAL ARTICLE
AU  - Tomlinson, David
AU  - Myles, Madison
AU  - Stevens, Kara
AU  - Streeter, Adam J
TI  - Transmural unipolar electrogram morphology is achieved within 7s at the posterior left atrial wall during pulmonary vein isolation: VISITAG™ Module-based lesion assessment during radiofrequency ablation
DP  - 2017 Jan 01
TA  - bioRxiv
4099  - http://biorxiv.org/content/early/2017/12/15/234799.short
4100  - http://biorxiv.org/content/early/2017/12/15/234799.full
AB  - Aims: To assess the occurrence of a histologically validated measure of transmural (TM) atrial ablation - pure R unipolar electrogram (UE) morphology change - at first-ablated left atrial posterior wall (LAPW) sites during contact force (CF)-guided pulmonary vein isolation (PVI). Methods and results: Exported VISITAG™ Module and CARTOREPLAY™ (Biosense Webster Inc.) UE morphology data was retrospectively analysed in 23 consecutive patients undergoing PVI under general anaesthesia. PVI without spontaneous / dormant recovery was achieved in all, employing 16.3[3.2] minutes (mean [SD]) of temperature-controlled RF at 30W. All first-ablated LAPW sites demonstrated RS UE morphology pre-ablation, with RF-induced pure R UE morphology change in 98%. Time to pure R UE morphology was significantly shorter at left-sided LAPW sites (4.9[2.1] s versus 6.7[2.5] s; p=0.02), with significantly greater impedance drop (median 13.5Ω versus 9.9Ω; p=0.003). Importantly, neither the first-site RF duration (14.9 versus 15.0s) nor the maximum ablation catheter tip distance moved (during RF) were significantly different, yet the mean CF was significantly higher at right-sided sites (16.5g versus 11.2g; p=0.002). Concurrent impedance and objectively annotated bipolar electrogram (BE) data demonstrated 6-8Ω impedance drop and 30% BE decrease at the time of first pure R UE morphology change. Conclusion: Using objective ablation site annotation, TM UE morphology change was typically achieved within 7s at the LAPW, with significantly greater ablative effect evident at left-sided sites. The methodology described in this report represents a novel and scientifically more rigorous foundation towards future research into the biological effects of RF ablation in vivo.