Is the Abnormal Conduction Zone of the Left Atrium a Precursor to a Low
Voltage Area in Patients with Atrial Fibrillation?
Background: The abnormal conduction zone (ACZ) in the left atrium (LA)
has attracted attention as an arrhythmia source in atrial fibrillation
(AF). We investigated the hypothesis that the ACZ is related to the low
voltage area (LVA) or the LA anatomical contact areas (CoAs) with other
organs. Methods and Results: We studied 100 patients (49 non-paroxysmal
AF, 66 males, 67.9±9.9 years) who received catheter ablation for AF.
High-density LA mapping during high right atrial pacing was constructed.
Isochronal activation maps were created at 5-ms interval setting, and
the ACZ was identified on the activation map by locating a site with
isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s.
The LVA was defined as the following; mild (<1.3 mV), moderate
(<1.0 mV), and severe LVA (<0.5 mV). The CoAs
(ascending aorta-anterior LA, descending aorta-posterior LA, and
vertebrae-posterior LA) were assessed using computed tomography. The ACZ
was linearly distributed, and observed in 95 patients (95%). The ACZ
was most frequently observed in the anterior wall region (77%). A
longer ACZ was significantly associated with a larger LA size and a
prevalence of non-PAF. The 51.2±36.2% of ACZ overlapped with mild LVA,
32.9±32.8% of ACZ with moderate LVA, and 14.6±22.0% of ACZ with severe
LVA. In contrast, only 25.6±28.0 % of ACZ matched with the CoAs.
Conclusion: The abnormal conduction zone reflects LA electrical
remodeling and may be a precursor finding of the low voltage zone and
not the LA contact areas in patients with atrial fibrillation.