Attenuation of Spontaneous Baroreceptor Sensitivity following Concussion

Introduction Cardiovascular autonomic nervous system (CV-ANS) function is negatively impacted after concussion. The arterial baroreflex buffers pressor and depressor challenges through efferent modulation of cardiac chrono- and inotropism, and peripheral vascular tone. Baroreceptor sensitivity (BRS) reflects the capacity of the CV-ANS to accommodate dynamic metabolic demands in the periphery. The impact of concussion on BRS has yet to be defined. Methods CV-ANS assessment (e.g., electrocardiogram and beat-to-beat SBP) was performed the seated upright position at rest within 48 hours (V1) of concussion and 1 week later (V2) in 10 intercollegiate male athletes with concussion and 10 non-injured male athletes. Changes in heart rate (HR), SBP, high and low frequency HR variability (HF- and LF-HRV, respectively), LF-SBP variability and BRS for increasing (BRSn-Up) and decreasing (BRSn-Dn) SBP excursions, and overall BRS (BRSn-Avg) were assessed for differences at V1 and V2. Results The concussion (age: 20±1 years; height: 1.79±0.14 meters; weight: 83±10 kilograms) and control (age: 20±1 years; height: 1.78±0.10 meters; weight: 79±13 kilograms) groups were matched for demographics. Concussed athletes had a significantly reduced BRSn-Up, BRSn-Dn, and BRSn-Avg compared to controls at V1 or V2; these changes occurred without differences in conventional markers of CV-ANS function (e.g., HF-HRV, LF-HRV, LF-SBP), HR or SBP at either visit. Conclusions Reduced BRS is a post-concussive consequence of CV-ANS dysfunction during the first post-injury week. Because SBP was similar between groups, it may be speculated that reduced BRS was not afferent in origin, but represents a post-injury consequence of the central nervous system after injury. Address for Correspondence and Reprints: Michael F. La Fountaine, Ed.D., ATC, FACSM, Seton Hall University, Interprofessional Health Sciences (IHS) Campus, Building 123, 340 Kingsland Street, Nutley, NJ 07110. Phone: (973) 275-2918. Fax: (973) 275-2370. E-mail address: lafounmi@shu.edu Preparation of this manuscript was partially supported by the New Jersey Commission for Brain Injury Research Individual Research Grant #CBIR16IRG025. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by the ACSM. Conflicts of Interest: None to declare Accepted for publication October 2018. © 2018 American College of Sports Medicine

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