Measures of Cardioautonomic Dysfunction as Markers of Sport Related Concussion

Abstract

The field of concussion research is vast but lacking in uniformity when implementing or recommending evaluative protocols. Of the pathological characteristics associated with concussion, autonomic dysfunction includes but is not limited to a dysregulation of autonomic afferent and efferent pathways in both cortical and medullary regions, resulting in impaired intrinsic autoregulatory function influencing inotropic and chronotropic aspects of myocardial contractility, as well as vascular smooth muscle regulation (1,2). Popular methods of assessing autonomic function in the wake of a concussion include heart rate variability (HRV) analysis, blood pressure variability analysis (BPV), and spontaneous baroreceptor sensitivity (SBRS). This project aims to examine the impact of concussive trauma on cardioautonomic functioning and multilevel cardioautonomic integration across two studies in 65 otherwise healthy college-aged athletes, with a focus on heart rate variability, blood pressure variability, and the multilevel autonomic integration required for cardiac baroreflex functioning across six time epochs (baseline, days 1-3, days 4-7, days 8-11, days 12-15, and days 16+) using rest and rhythmic breathing portions (0.1 Hz) of the Neary Protocol. Two within-subject repeated-measures multilevel modelling approaches were used for statistical analysis to address non-equidistant sampling intervals present in the data set, with a Sidak post-hoc test for pairwise comparisons with alpha set at p<0.05. I conclude that rhythmic breathing is the preferred methodology to assess cardioautonomic dysfunction in the wake of a concussion, integrate heart rate variability and baroreceptor sensitivity values, and speculate about a potential mechanism responsible for patterns of cardioautonomic dysfunction to paint a picture of the multilevel autonomic integration that can be readily evaluated to diagnose concussion.