Abstract Body (Do not enter title and authors here): Introduction: Fluctuations of heart rate, or heart rate variability (HRV), contain important information about autonomic functions and regulations of the cardiovascular system. Heart rate fragmentation (HRF) is an inter-beat interval dynamics approach (Front Physiol, 2017 PMID: 29184505) that enhances analysis of short-term HRV. HRF has shown consistency with breakdown of neuroautonomic-electrophysiologic control system of the sino-atrial node. Here, we evaluate alterations of HRF metrics prior to, during the ischemic stroke and after reperfusion.
Methods: We used the standard ischemic stroke model (intraluminal suture middle cerebral artery (MCA) occlusion) in adult male/female Sprague Dawley rats (n=11, 2-3 months old, weight: 296 ± 47 g, 27% female). The common carotid artery (CCA) was temporarily occluded while a suture was introduced to the internal carotid artery and advanced until it interrupted blood supply to MCA. We occluded the MCA for 1 hour followed by 3 hours of reperfusion (Fig.1). Electrocardiogram (ECG) was continuously measured throughout the surgeries. Post-surgery, the presence of cerebral infarction was confirmed by incubating brain slices in triphenyl tetrazolium chloride (TTC staining). HRF metrics were computed using 1-minute recordings of ECG at 3 time-points: a) baseline; b) 1 hour after MCA occlusion (pre-reperfusion); and c) 3 hours after reperfusion.
Results: Significant differences (p<0.05) were found between the baseline and 3 hours after reperfusion (Fig.2) for two HRF metrics: PIP% (percentage of inflection points i.e., changes in heart rate acceleration sign) and W1% (percentage of only 1 inflection point in sequences of five consecutive heart rate intervals).
Conclusions: Our results suggest that there are specific HRF metrics that alter significantly after ischemic stroke in rats. This study shows the possibility of developing noninvasive HRF-based techniques for detection or monitoring of ischemic stroke and treatment in future.