Clinical Electrophysiology -> Atrial Fibrillation & Atrial Flutter: -> Physiology D-PO01 - Featured Poster Session (ID 11) Poster

D-PO01-019 - Electrophysiological Characteristics Of Post-Ablation Peri-mitral Flutter (ID 882)


Background: Despite advances in high-density mapping of mitral flutter, ablation remains challenging. A more comprehensive understanding of the reentrant circuit of mitral flutter (MFL) may improve selection of sites for ablation.
Objective: In the current study, we characterized the electrophysiological properties of reentrant circuits of MFL by using high-resolution mapping technology.
Methods: 12 patients (age 66 ± 12, 9 males) undergoing redo AF ablation with MFL after pulmonary vein isolation with/without substrate modification were included. Activation mapping was performed using the Rhythmia mapping system (Boston Scientific). MFL was defined as a completely closed loop circulating along the mitral annulus with total conduction time equal to tachycardia cycle length (TCL). Conduction delay zone was identified qualitatively by narrowing of the isochronal line interval of >50% on color-coded isochronal map where each color represented 10% of TCL. The sites of ablation that directly terminated MFL were retrospectively reviewed.
Results: MFL (n=12, CL 256 ± 48 msec) included 7 clockwise and 5 counterclockwise. We identified two patterns of MFL activation: In Group I, 7 MFL had two reentrant circuits sharing a common pathway (Figure of 8) and in Group II, 5 had a solitary reentrant loop. Zones of slow conduction around mitral annulus were quantified: 7 patients had 2 zones and 5 a single zone. The locations of slow conduction zones around mitral annulus were as follows: 5 inferolateral, 5 anterior, 4 anterolateral, 3 septal, 1 lateral, 1 inferior. In Group I, the region with marked conduction slowing in the co-dominant loop of MFL was found at the area of left PVs (n=3), anterior wall (n=3), and RIPV (n=1). In 8 of 9, successful termination sites corresponded to conduction delay zones.
Conclusion: We found that 1) post-ablation MFL was almost evenly split between single and double loop reentry, 2) always had at least one distinct slow conduction zone along the mitral annulus, 3) the presence of a second loop is dependent on the presence of slow conduction zone outside primary mitral circuit, and 4) successful ablation sites were mostly seen in conduction delay area. Ablation targeting area of slow conduction may be preferred to standard anatomical mitral isthmus ablation.