Abstract WP153: Relative Risk of Atrial Fibrillation Detection with Prolonged External Cardiac Monitoring and MRI Infarct Patterns.

Background and Aim: Current guidelines recommend prolonged rhythm monitoring for up to 30 days in patients with cryptogenic stroke/embolic stroke of undetermined source (ESUS). The role of monitoring in patients with lacunar infarcts, is unknown. We conducted a multicenter retrospective cohort study aimed at determining the atrial fibrillation (AF) detection yield in patients with MRI defined infarct patterns. Methods: An ECM database was used to identify patients from stroke units across a single state. Patients were included if an MRI with Diffusion-Weighted Imaging (DWI) sequences was obtained and ECM was initiated within 30 days of stroke. Image analysis included DWI lesion diameter, planimetric volume measurement and Fazekas scale scoring. Infarcts were classified as embolic/lacunar (isolated subcortical DWI lesions, diameter <20mm)/none, and the rate of AF detection in each group was determined from the ECM. Results: A total of 1,924 patients underwent ECM between July 2017 and December 2021, of whom 1438 (74.7%) had MRI. The mean±SD age was 65±16 and 40.1% were women. The overall rate of AF was 68/1438 (4.7%). AF frequency differed between infarct pattern groups (48/679, 7.1% embolic pattern, 7/214, 3.3% lacunar infarcts, and 13/545, 2.4% with TIA (p<0.001). The risk ratio [95% CI] of AF was higher patients with an embolic infarct than those with a TIA (RR 2.96, [1.62, 5.41], p<0.001). Although numerically more common in embolic infarction, the risk of AF was not significantly greater than those with lacunar infarcts (RR 2.16, [0.99,4.70], p=0.0495). A Poisson regression analysis adjusting for age/sex indicated that multiple vascular territory involvement was not associated with AF detection (RR 1.68, [0.93,3.04], p=0.121). There was a borderline association with bilateral infarction (RR 1.94, [1.03,3.63], p=0.048). Infarct volume was not independently associated with AF (RR 0.92 per 10 ml increase, [0.75,1.13], p=0.44). Lacunar infarction was associated with higher Fazekas scores (adjusted mean difference cf. embolic pattern +0.26, [0.13, 0.40], p<0.001). Fazekas scores (2–3 vs 0–1) were not associated with AF (RR 1.16, [0.59,2.30], p=0.66). Conclusions: Paroxysmal AF is common after both embolic and lacunar infarction. Although the absolute yield is lower, prolonged ECM has utility in patients with lacunar infarcts, irrespective of small vessel disease markers.