Left Atrial Strain Impairment in Embolic Stroke of Undetermined Source: A Systematic Review and Meta-Analysis.

Embolic stroke of undetermined source (ESUS) accounts for approximately one-third of all ischemic strokes. Atrial cardiomyopathy, independent of paroxysmal atrial fibrillation, is an increasingly recognized embolic substrate. Left atrial (LA) strain assessed by speckle-tracking echocardiography or cardiac magnetic resonance provides a sensitive, noninvasive measure of subclinical atrial mechanical dysfunction that precedes chamber enlargement. This systematic review and meta-analysis synthesizes evidence on all 3 LA strain phases in ESUS through July 2026. Seven studies met the inclusion criteria; 5 provided extractable quantitative data for meta-analysis (n = 656, n = 40, n = 56, n = 82, and n = 459; total N = 1293). ESUS patients demonstrated significantly reduced LA reservoir strain [mean difference (MD) = -4.43%, 95% confidence interval (CI), -6.77 to -2.09; I2 = 82.25%; P = 0.0002], LA conduit strain (LAScd) (MD = -1.69%, 95% CI, -2.20 to -1.18; I2 = 0.00%; P < 0.0001), and LA contractile strain (MD = -2.24%, 95% CI, -3.34 to -1.14; I2 = 69.92%; P < 0.0001). LAScd I2 = 0.00% indicates remarkably consistent conduit impairment across all 5 studies. All 5 meta-analytic studies achieved a Newcastle-Ottawa Scale score of ≥7. All 3 LA strain phases are consistently and significantly impaired in ESUS patients versus controls. Near-zero LAScd heterogeneity identifies conduit strain as the most reproducible marker of atrial cardiomyopathy in ESUS. These findings support subclinical atrial cardiomyopathy as an embolic substrate independent of atrial fibrillation. Large, prospective, standardized multicenter studies are required before clinical translation.