Exploring the Role of Left Atrial Fibrosis and Left Atrial Volume Index Through Cardiac Magnetic Resonance Imaging in Embolic Stroke of Undetermined Source: A Network Meta-Analysis.

Objectives: Left atrial fibrosis (LAF) and left atrial volume index (LAVI), assessed via cardiac magnetic resonance (CMR), are emerging biomarkers for atrial cardiomyopathy and stroke risk. Their roles in the embolic stroke of undetermined source (ESUS) remain unclear. This study evaluates LAF and LAVI in ESUS and explores whether age modifies these outcomes.

Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO CRD42024615479), we searched eight databases (inception-October 2024) for studies evaluating LAF or LAVI via CMR in ESUS, compared to atrial fibrillation (AF) without stroke, cardioembolic stroke (CES), non-cardioembolic stroke (NCE), and healthy controls. We performed a Bayesian network meta-analysis to estimate mean differences (MD) with 95% credible intervals (CrI). Node-splitting tested consistency, and a meta-regression examined the effect of age.

Results: Ten observational studies with 1,285 patients (mean age 65.1 ± 12.1 years) were included, demonstrating a generally low risk of bias. ESUS patients had significantly higher LAF than healthy controls (MD 9.86%, 95% CrI 3.05%-16.62%). No significant LAF differences were found between ESUS and AF without stroke, CES, or NCE. LAVI did not differ significantly between ESUS and any comparator groups. Node-splitting indicated no inconsistencies. Age was not significantly associated with LAF or LAVI.

Conclusion: ESUS patients show increased LAF compared to healthy individuals, suggesting a key role of LAF in ESUS pathogenesis. Nonetheless, the application of CMR-detected LAF as a prognostic biomarker requires prospective validation to confirm its clinical utility in predicting stroke recurrence.