Background: The multiple wavelets and functional re‐entry hypotheses are
mechanistic theories to explain atrial fibrillation (AF). If valid, a chamber's ability to
support AF should depend upon the left atrial size, conduction velocity (CV), and
refractoriness. Measurement of these parameters could provide a new therapeutic
target for AF. We investigated the relationship between left atrial effective
conducting size (LAECS), a function of area, CV and refractoriness, and AF
vulnerability in patients undergoing AF ablation.
Methods and Results: Activation mapping was performed in patients with
paroxysmal (n = 21) and persistent AF (n = 18) undergoing pulmonary vein isolation.
Parameters used for calculating LAECS were: (a) left atrial body area (A); (b) effective
refractory period (ERP); and (c) total activation time (T). Global CV was estimated as
√A/T. Effective atrial conducting size was calculated as LAECS = A/(CV × ERP). Post
ablation, AF inducibility testing was performed. The critical LAECS required for
multiple wavelet termination was determined from computational modeling. LAECS
was greater in patients with persistent vs paroxysmal AF (4.4 ± 2.0 cm vs 3.2 ± 1.4 cm;
P = .049). AF was inducible in 14/39 patients. LAECS was greater in AF‐inducible
patients (4.4 ± 1.8 cm vs 3.3 ± 1.7 cm; P = .035, respectively). The difference in LAECS
between inducible and noninducible patients was significant in patients with
persistent (P = .0046) but not paroxysmal AF (P = .6359). Computational modeling
confirmed that LAECS > 4 cm was required for continuation of AF.
- atrial fibrillation vulnerability
- conduction velocity
- left atrial effective conducting size