Abstract Body: Introduction: Heart rate variability (HRV), which represents fluctuations in heart rate, provides critical insights into autonomic regulation and cardiovascular function. This study aims to evaluate how HRV metrics change before, during, and after an ischemic stroke in a rat model, with a focus on understanding the impact of stroke and subsequent reperfusion on autonomic control.

Methods: We employed the standard intraluminal suture middle cerebral artery (MCA) occlusion model to induce ischemic stroke in anesthetized adult male and female Sprague Dawley rats (n=11, 2-3 months old, average body weight: 296 ± 47 g, 27% female). The procedure involved temporary occlusion of the common carotid artery (CCA) while advancing a suture into the internal carotid artery to occlude the MCA for 1 hour, followed by 3 hours of reperfusion (Fig. 1). Electrocardiogram (ECG) signals were continuously recorded throughout the procedure. Post-surgery, cerebral infarction was confirmed via the triphenyl tetrazolium chloride (TTC) staining technique. HRV metrics were analyzed from 1-minute ECG recordings taken at three time points: baseline, 1 hour post-MCA occlusion (pre-reperfusion), and 3 hours post-reperfusion.

Results and Conclusions: Significant alterations in HRV metrics were observed between baseline and 3 hours after reperfusion (p<0.05; Fig. 2; see figure’s caption for the metric descriptions). Specifically, high-frequency relative power percentage (HF%) and the SD1/SD2 ratio decreased significantly, while low-frequency relative power percentage (LF%) and the LF/HF ratio increased significantly. Additionally, the LF/HF power ratio showed a notable increase from baseline to 1 hour post-MCA occlusion. Our findings reveal distinct HRV metric changes associated with the ischemic stroke. The observed alterations reflect a shift of autonomic regulation towards sympathetic dominance, which intensifies after reperfusion, supporting other preclinical and clinical findings. These results suggest the potential for developing non-invasive, HRV-based techniques for real-time detection and monitoring of ischemic stroke. Further research could enhance these techniques' applicability in clinical settings.