Temporal morphological changes of the left atrial appendage after electrical isolation: implications for optimal timing of LAA occlusion

Background During atrial fibrillation ablation, the left atrial appendage (LAA) can be intentionally or unintentionally isolated electrically. Once isolated, the LAA loses its contractile function and becomes highly thrombogenic, for which left atrial appendage occlusion (LAAO) is recommended. However, the morphology of the LAA may change over time after isolation, and the optimal timing of LAAO following LAA isolation remains unclear. Objective This study aimed to compare morphological changes in the LAA between patients who underwent LAAO in the acute phase (≤90 days) and those in the chronic phase (>90 days) after electrical isolation, and to investigate the optimal timing for LAA closure. Methods Patients were divided into two groups based on the interval between LAA isolation and LAAO: an acute-phase group (≤90 days) and a chronic-phase group (>90 days).A total of 10 patients who underwent LAAO after LAA isolation were included (5 in each group). Transesophageal echocardiography was performed to measure the LAA ostial diameter, depth, area, and volume both before isolation and immediately before LAAO. Results The median interval between isolation and LAAO was 27 days [7–30] in the acute-phase group and 150 days [91–270] in the chronic-phase group. All patients continued appropriate doses of DOAC therapy until LAAO, and no thromboembolic or major bleeding events occurred during the waiting period. The changes in LAA ostial diameter were −0.56±2.93 mm vs. −1.86±0.55 mm (p=0.36), with corresponding percentage changes of −0.8±10.4% vs. −6.6±3.7%.LAA depth changes were +2.56±4.91 mm vs. −2.08±7.88 mm (p=0.30), with percentage changes of +10.7±19.2% vs. −6.7±21.9%. In contrast, LAA volume showed opposite trends between groups:+4.10±3.86 mL (+39.9±23.6%) in the acute phase and −3.78±4.04 mL (−19.8±23.4%) in the chronic phase, demonstrating a significant difference (p=0.034). Conclusion After electrical isolation, the LAA exhibits a biphasic morphological change—transient enlargement in the acute phase and gradual reduction in the chronic phase.Therefore, both device sizing and procedural timing for LAAO should take into account the temporal remodeling of the LAA according to the interval since isolation.Understanding this time-dependent remodeling process may contribute to the optimization of a safer and more rational strategy for left atrial appendage closure.