PO-02-172 CONDUCTION VELOCITY AND CONDUCTION VELOCITY DYNAMICS IN THE LEFT ATRIUM ARE IMPACTED BY STRUCTURAL AND AUTONOMIC MODULATION AND SITES OF CONDUCTION VELOCITY HETEROGENEITY CORRELATE TO RE-ENTRY ACTIVITY IN ATRIAL FIBRILLATION

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Structural and autonomic remodelling is proposed to drive atrial fibrillation (AF). Conduction velocity (CV) heterogeneity predisposes cardiac tissue to re-entry mechanisms. The impact of structural and autonomic remodelling on CV dynamics and re-entry formation is unclear. Evaluate the impact structural and autonomic modulation has on CV dynamics and re-entry activity in AF. Local activation times (LATs), voltage and geometry data were obtained from 20 patients undergoing catheter ablation for persistent AF. LATs were obtained at 3 pacing intervals (PI) (600, 400 and 250ms) with pacing from two pacing sites. LATs were used to determine CV dynamics and their relationship to voltage using an automated algorithm. Relationship between sites of enhanced CV heterogeneity defined as rate dependent CV slowing (RDCV) sites (sites exhibiting CV difference (CVd) between PI=600ms and PI=250ms of ≥20% of the mean CVd seen between these PIs for that voltage zone) and re-entry activity in AF was evaluated. Re-entry activity was identified using an automated algorithm and defined as ≥1.5 rotations of 360 degrees. The impact of autonomic modulation on CV dynamics both pharmacologically and with ganglionated plexi stimulation was assessed. A total of 512,082 LAT and voltage points were analysed. Voltage impacts CV (1.36±0.98 nLVZ ≥0.5mV, 1.05±1.03 LVZ 0.2-0.49mV and 0.58±0.37 vLVZ <0.2mV) (Figure 1A-B) and CV dynamics, whereby at nLVZ the curves are steeper (0.03±0.02ms CVd PI 600-400ms, 0.54±1.1ms CVd PI 400-250ms), broader at LVZ (0.16±0.09ms CVd PI 600-400ms, 0.23±1.1ms CVd PI 400-250ms) and flat at vLVZ (0.04±0.01ms CVd PI 600-400ms, 0.05±0.02ms CVd PI 400-250ms) (Figure 1C). Per patient, 5.6±1.1 RDCV sites and 3.4±1.3 sites of re-entry activity were identified. Of the RDCV sites, 72.3% (81/112) correlated to 94.1% (64/68) of re-entry activity sites which were mainly confined to LVZs (59/68, 86.8%). Autonomic modulation affected the CV dynamic curves through increasing rate dependency slowing (Figure 1D). The number of RDCV sites identified were enhanced following autonomic modulation (3.4±1.2 increase per patient). CVs and CV dynamics are impacted by structural remodelling and are influenced by autonomic modulation which enhances CV heterogeneity. CV heterogeneity sites correlate to re-entry activity in AF. Assessment of CV dynamics and heterogenity may help to determine the mechanistic importance of LVZs.