ABSTRACT NUMBER: ESOC2026A1440 DISTINCT ISCHEMIC STROKE LESION PATTERNS ACROSS ATRIAL FIBRILLATION SUBGROUPS: A VOXEL-BASED LESION MAPPING STUDY

Abstract Background and aims Atrial fibrillation detected after stroke (AFDAS) by prolonged cardiac monitoring may reflect different pathophysiological mechanisms and embolic risk compared with AF newly detected on surface ECG (ECG-AF) and AF known before stroke (KAF). We hypothesized that ischemic stroke lesion topography differs across these AF subtypes. We compared voxel-wise lesion distributions among patients with KAF, ECG-AF, and AFDAS, and explored whether spatial differences could relate to embolic characteristics or involvement of brain regions associated with autonomic control. Methods We analyzed 351 consecutive ischemic stroke patients from a prospective registry: KAF (n=150), AFDAS (n=74), and ECG-AF (n=127). Acute diffusion-weighted imaging lesions were segmented and normalized to Montreal Neurological Institute space. Voxel-wise group comparisons were performed using probabilistic threshold-free cluster enhancement with family-wise error correction (p<0.05). Pairwise comparisons included KAF vs AFDAS, ECG-AF vs AFDAS, and KAF vs ECG-AF. Results Significant voxel-wise lesion pattern differences were observed between AFDAS and both KAF and ECG-AF groups. Compared with AFDAS, KAF patients showed a posterior cluster of 1,847 voxels predominantly involving the lingual gyrus and occipital pole. Similar posterior clusters were observed in ECG-AF vs AFDAS comparisons, mainly involving the lingual and occipital fusiform gyri. No statistically significant voxel-wise differences were identified between KAF and ECG-AF groups. Conclusions AFDAS is associated with distinct ischemic stroke lesion patterns compared with KAF and ECG-AF, characterized by relative sparing of posterior cerebral regions. These findings support biological heterogeneity within AF-related stroke and suggest that embolic properties and autonomic network involvement may differentially influence atrial arrhythmogenesis in AFDAS. Conflict of interest Sebastian Fridman: nothing to disclose. Luciano Sposato: nothing to disclose. Alonso Alvarado Bolaños: nothing to disclose. Maria Bres Bullrich: nothing to disclose. Diana Ayan: nothing to disclose. Figure 1 - belongs to Conclusions