Measures of Heart‐Rate Variability Immediately Post Concussion
Authors: Iring Stephanie , Favre Michelle , Del La Cruz Leslie , Sammy Bishoy , Liu Jie , Serrador Jorge 
Published: April 2020

There 1.6 to 3.8 million sports‐related concussions reported annually. Despite the growing number of sports‐related concussions, there is a lack of evidence‐based methods to evaluate, treat, predict, and monitor recovery in affected athletes. The pathophysiology undermining the changes in the brain post injury remains unknown. Increasing studies have shown there is autonomic nervous system (ANS) dysfunction following brain injury. Heart rate variability can be used as a method to measure autonomic nervous system anomalies to aid in the detection of concussions. To obtain this data we have developed a mobile tent‐based laboratory that allows us to gather data on the field during a rugby match. Data were collected acutely post‐injury to provide a rapid assessment of concussion effects on the cerebrovascular physiology. The conditions are that athletes all played in a rugby match before enrolling in the study. If the athlete experienced an injury, they had to be assessed by a medical team who classified them as having a concussion. If they did not require any further medical treatment, they were given the option to participate in our study. To assess the autonomic effects of concussion we measured beat‐by‐beat blood pressure (Finometer), heart rate, common and internal carotid blood flow, and end‐tidal CO2 using a nasal cannula during rest, both in the seated and supine position. In a subgroup of 15 players collected last August (6 controls, 9 concussed, Mean age= 30, range= 19–66 yrs) out of our large study (195 players (88 with concussions) we had players perform a SCAT total number of symptoms as well as Symptom Severity Score. Concussed players had significantly higher SCAT total number of symptoms (8 ± 3 vs 4 ± 3, P=0.04) and trending towards a higher Symptom Severity Score (23± 14 vs 10 ± 9, P=0.08). Mean RR Interval in concussed players (seated: 685 ± 41 vs supine: 720 ± 61 ms) compared to controls (seated: 734 ± 90 vs supine: 786 ± 90 ms). Examining postural changes in heart rate variability we found that concussed players demonstrated significant changes in the Low Frequency (LF) ratio seated/supine (Concussed: 1.09 ± 0.47 v Controls: 0.46 ± 0.16) and no change in the High Frequency (HF) ratio seated/supine (Concussed: 0.61 ± 0.21 vs Controls: 0.77 ± 0.29, P=0.3). The SCAT total number of symptoms was significantly correlated to ratio of seated/supine in the LF range in concussed players (r=0.71, P=0.03) but not the HF ratio (r=.48, P=.18). This subset of data suggests that there are changes in heart rate variability immediately post‐concussion, which may be correlated with the number of symptoms following a hit to the head. This data also supports that measures are dependent on posture. The LF frequency increases in the seated position in concussed players suggesting an increase in sympathetic activity, compared to decreasing in controls. Future work is needed to examine how immediate measures of heart rate and brain blood flow in seated and supine are predictive of concussion outcomes.

Support or Funding Information

This work was supported by Dept. of Pharmacology, Physiology, and Neuroscience, Rutgers.