Assessment of Left Atrial Fibrosis by Cardiac Magnetic Resonance Imaging in Ischemic Stroke Patients Without Atrial Fibrillation: A Systematic Review and Meta-Analysis.

Background: Left atrial (LA) fibrosis is a marker of atrial cardiomyopathy and has been reported to be associated with both atrial fibrillation and ischemic stroke. Elucidating this relationship is clinically important as LA fibrosis could serve as a surrogate biomarker of LA cardiomyopathy. The objective of this study is to investigate the association of LA fibrosis and embolic stroke of undetermined source (ESUS) using cardiac magnetic resonance imaging.

Methods And Results: Following an International Prospective Register of Systematic Reviews-registered protocol, 3 blinded reviewers performed a systematic review for studies that quantified the degree of LA fibrosis in patients with ESUS as compared with healthy patients from inception to February 2024. A meta-analysis was conducted in the mean difference. From 7 studies (705 patients), there was a significantly higher degree of LA fibrosis in patients with ESUS compared with healthy controls (MD, 5.71% [95% CI, 3.55%-7.87%], <0.01). The degree of LA fibrosis was significantly higher in patients with atrial fibrillation than healthy controls (MD, 8.22% [95% CI, 5.62%-10.83%], <0.01). A similar degree of LA fibrosis was observed in patients with ESUS compared with patients with atrial fibrillation (MD, -0.92% [95% CI, -2.29% to 0.44%], =0.35).

Conclusions: A significantly higher degree of LA fibrosis was found in patients with ESUS as compared with healthy controls. This suggests that LA fibrosis may play a significant role in the pathogenesis of ESUS. Further research is warranted to investigate LA fibrosis as a surrogate biomarker of atrial cardiomyopathy and recurrent stroke risk in patients with ESUS.