Advertisement

CE-520-01 PULMONARY VEIN MYOCARDIAL SLEEVES ACT AS AMPLIFIER SITES DURING PERSISTENT ATRIAL FIBRILLATION: A HIGH DENSITY PHASE MAPPING STUDY

      Background

      The mechanisms underlying persistent AF (PeAF) remain poorly defined. Although the substrate is not limited to the pulmonary veins (PVs), PV isolation (PVI) remains the best ablation strategy in PeAF.

      Objective

      To characterise the mechanisms of electrical activity originating in the PV sleeves during PeAF.

      Methods

      Eleven patients presenting for first time ablation for PeAF were recruited (63.1 ± 10.9 years, 91% males). Prior to PVI, a 64 electrode catheter (ConstellationTM; 38 mm) was introduced into the left atrium (LA) via trans septal access and positioned within the PV including the antral region under fluoroscopic guidance. A robust inverse mapping technique was used to reconstruct unipolar atrial EGMs on the PV surface and the resulting phase maps were used to identify incoming and outgoing wavefronts (WF) at the PV junction (reentry), and focal and rotor activity originating within the PV sleeves. These events were overlaid on phase entropy-time plots that reflect activation and repolarization heterogeneity across the PV surface. Data were analysed over 10 secs periods and are presented as median [LQ; UQ] or mean+SD, if normally distributed.

      Results

      During PeAF, the PVs gave rise to outgoing WF with frequency 3.7Hz [3.4; 5.4]. The most common mechanism generating outgoing WF was circuitous macroscopic reentry where an incoming WF generated one or more outgoing WF (frequency of reentry 2.7Hz [1.9; 3.3] compared with focal activity 1.4Hz [1.05; 1.5] (p<0.001). Rotors within the PV sleeve were rarely observed. Reentrant delay (time from wave-front entering to time of reentrant exit from the PV sleeve) was remarkably consistent between patients (125+46ms, range 30-260 ms, n=282). Higher outgoing frequencies were associated with repeated cycles of reentry (1 incoming wave generating 2 or more reentrant outgoing WF) and elevated phase entropy (R2 = 0.94 and 0.93, respectively, p<0.001). The median ratio of incoming to outgoing PV activity was 1.14 (LQ=0.84, UQ=1.88). In 6/11 PVs (55%) the R was >1 (Mean 1.77±0.54, maximum 2.68).

      Conclusion

      Electrical activity generated by PV sleeves during PeAF is due mainly to macroscopic reentry initiated by incoming waves, frequently with a ratio>1. That is, the PVs act less as AF drivers than as “echo chambers” which sustain and amplify fibrillatory activity.