Introduction:
The slow conduction zone (SCZ) in the left atrium (LA) has attracted attention as an arrhythmia substrate of atrial fibrillation (AF). However, the occurrence mechanism of SCZ remains unclear.
Hypothesis:
The SCZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs in patients with AF.
Methods:
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 right atrial appendage pacing at a rate of 100 bpm after pulmonary vein isolation were constructed. Isochronal activation maps were created at 5-ms interval setting, and the SCZ was identified on the activation map by finding a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s (Figure). 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.
Results:
The SCZ was distributed linearly (Figure), and observed in 95 of 100 patients (95%). The SCZ was most frequently observed in the anterior wall region (77%). A longer SCZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2±36.2% of SCZ overlapped with mild LVA, 32.9±32.8% of SCZ with moderate LVA, and 14.6±22.0% of SCZ with severe LVA. In contrast, only 25.6±28.0 % of SCZ matched with the CoAs.
Conclusion:
The slow conduction zone reflects LA electrical remodeling and may be a precursor finding of the low voltage zone, not LA contact areas in patients with atrial fibrillation.
Adenosine-sensitive atrial tachycardia originating from the para-Hisian region with a slow conduction zone in the anteroseptal left atrium