Heart Rate Variability Dynamics as Predictors of Functional Recovery and Mortality After Acute Ischemic Stroke

Abstract

Background: Autonomic dysfunction is commonly encountered after acute ischemic stroke (AIS) and may influence both functional recovery and survival. Heart rate variability (HRV) provides a non-invasive measure of autonomic balance, but its temporal evolution and prognostic significance in AIS remain insufficiently evaluated. Methods: In this prospective observational study, 148 AIS patients (mean age of 65.93 ± 9.19 years) underwent HRV assessment at baseline, one month, and three months follow-up, between January 2022 and October 2024. Time and frequency domain parameters, including Standard Deviation of NN intervals (SDNN), Low-Frequency (LF) power, High-Frequency (HF) power, and LF/HF ratio, were analyzed. Functional outcome was assessed using the modified Rankin Scale (mRS), with a good outcome defined as mRS ≤ 2. Multivariable logistic regression identified independent predictors of poor outcome (mRS > 2) at each time point. Mortality was recorded at one and three months, and potential predictors were evaluated. Results: Over three months, SDNN increased by 34.84% (p < 0.001), HF power rose by 22.26% (p < 0.001), LF power decreased by 21.61% (p < 0.001), and LF/HF ratio declined by 35.41% (p < 0.001), indicating a shift toward parasympathetic predominance. Higher SDNN correlated strongly with better functional status and was an important predictor of favorable outcome at all time points (p < 0.001). Higher LF/HF ratio predicted poor outcome at baseline (p < 0.01) and three months (p < 0.001). At three months, mortality reached 12.2%, with significant predictors including coronary artery disease (CAD), heart failure (HF), chronic kidney disease (CKD), and altered HRV parameters. Conclusions: Post-stroke recovery is characterized by the progressive restoration of autonomic balance, with higher SDNN and lower LF/HF associated with improved functional recovery and survival. HRV analysis offers valuable prognostic insight and may aid in risk stratification after AIS.

Keywords: acute ischemic stroke; autonomic dysfunction; functional outcome; heart rate variability (HRV); modified Rankin Scale.

Figure 1

Flow diagram of study population selection.

Figure 2

SDNN progression over time. Boxplots show the median and interquartile range with whiskers representing the data spread; individual gray dots indicate patient values; the green line connects group means across time points. Reported p-values (p < 0.001 for all intervals) were obtained from LMMs after log transformation.

Figure 3

LF/HF progression over time. Boxplots show the median and interquartile range with whiskers representing the data spread; individual gray dots indicate patient values; the green line connects group means across time points. Reported p-values (p < 0.001 for all intervals) were obtained from LMMs after log transformation.

Figure 4

Survival probability over time. Red line represents the survival probability; grey area represents the confidence interval (95%).

Figure 5

Mortality predictors. Cells marked with * represent non-significant results with p values greater than 0.05.