Statistical Analysis
We compared demographic, clinical, and laboratory data between the two groups using t-tests for continuous variables and Fisher’s exact tests for categorical variables. LA strain was divided into three components—LA reservoir, conduit, and contractile—to determine the association of each phase of atrial function with stroke subtypes. Multivariable logistic regression analysis adjusting for covariates was performed. The first model was adjusted for age and sex. The second model was adjusted for covariates in model 1 plus systolic blood pressure, history of congestive heart failure defined as heart failure with mid-range and preserved ejection fraction according to the guidelines from the Heart Failure Society of America25, and NIHSS. LA strain components (reservoir, conduit, and contractile) were assessed both as linear and tertile categorical variables to simplify the analysis for easier interpretation and to study the trend within the LA strain dataset. All ESUS patients were give a prescription of cardiac event monitor (CEM). Those with negative CEM were given implantable loop recorders (ILR). The presence of AF was defined as identification of AF for more than 30 seconds on monitoring.
We compared three phases of LA strain between all ESUS patients with and without AF detection using t-tests. The association between LA strain and detection of AF was assessed using logistic regression analysis. Sensitivity analyses were performed adjusting for age, focusing only on ESUS patients who received cardiac monitoring, and focusing only on ESUS patients found to have AF on cardiac monitoring to compare differences in LA strain between those with an AF burden of less than 24 hours versus greater than or equal to 24 hours. Analysis was performed using STATA SE v17 with a p-value < 0.05 as statistically significant.