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British Journal of Healthcare and Medical Research - Vol. 11, No. 5

Publication Date: October 25, 2024

DOI:10.14738/bjhmr.115.17614.

Avdeev, W. (2024). A Review of the Cardiovascular Consequences of Concussion and Mild Traumatic Brain Injury. British Journal of

Healthcare and Medical Research, Vol - 11(5). 65-68.

Services for Science and Education – United Kingdom

A Review of the Cardiovascular Consequences of Concussion and

Mild Traumatic Brain Injury

William Avdeev

Case Western Reserve University

ABSTRACT

Objection: During 2010-2016, approximately 2.7 million annual emergency

department visits for sport injuries were made by patients ages 5 to 24 years old.

Injuries in professional sports have been reported as high as 49.4 per 1000 athletes

in ice hockey, 64.7 in football, 19.3 in basketball and 3.61 in baseball. Sports-related

injuries, specifically concussions, have healthcare costs as well as long-term

physical and psychological implications. As the result, sports medicine

professionals and organizations have attempted to implement injury risk reduction

strategies and promote safe sport participation. Methods: This study examines

several existing studies of concussion injuries and their impact on cardio-vascular

health and draws conclusions and recommendations based on their review.

Literature search was conducted using ABI Business Periodicals Database. Three

studies were examined, and conclusions were drawn based on their findings. In

addition, based on the findings in the published studies, inferences were drawn for

further research and examination. Results: Athletes with concussion history display

suppressed cardiac autonomic recovery after moderate aerobic exercise, compared

to those who did not suffer any concussion injuries. Players with multiple previous

concussions displayed increased time to physiological recovery after moderate

exercise compared to athletes with only one or no concussions. Conclusion: This

paper will discuss the need to respond to these statistics. Further studies are

needed to examine the long-term effect of concussion injuries, where social and

economic impacts also cannot be overlooked.

INTRODUCTION

Immediate consequences on cognitive function are acknowledged as a harmful result of

concussion injuries. Historically, concussions were feared primarily due to their association

with direct psychological issues such as cognitive deficits or neurological symptoms like

headaches. However, new studies suggest that the ramifications of concussions are not

confined to neurological effects and can have severe cardiovascular implications through

disruptions in heart rate variability (HRV).

HRV is an important index of autonomic nervous system (ANS) function, which reflects the

variation in time intervals between heartbeats. This paper will further examine the complex

nature of concussion-related injury to both brain and cardiovascular health, with particular

emphasis on disruption in autonomic function, monitoring using HRV markers as biomarkers

during recovery, and their practical utility for implementation within a biofeedback

intervention during rehabilitation. The analysis presented in this article is based on the relevant

inferences and recommendations drawn from the relevant literature review.

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British Journal of Healthcare and Medical Research (BJHMR) Vol 11, Issue 05, October-2024

Services for Science and Education – United Kingdom

CONCUSSIONS AND AUTONOMIC DYSFUNCTION

Not only can a concussion result in profound autonomic dysfunction, but also this is classically

demonstrated by changes to HRV. A critical role of the autonomic nervous system, which

controls vital functions (i.e., heart rate, digestion, and respiratory rate), is impaired after a

concussion. The ANS comprises the sympathetic (fight or flight) and parasympathetic (rest and

digest) branches, of which HRV is a measure that dynamically balances these two branches.

Regarding concussive brain injury, many studies have shown a decrease in HRV, signifying

increased sympathetic tone and decreased parasympathetic action—a state of autonomic

dysregulation. This autonomic dysregulation is not only acutely induced after sports-related

concussion but may be prolonged even beyond the resolution of conventional markers for

sustained symptom clearance. HRV may serve as a valuable performance measure, improving

our understanding of recovery following mTBI/SPRTC injury. This reciprocal relationship

between the brain and cardiovascular system indicates that not only cognitive and neurological

symptoms but also cardiovascular regulation may be impaired by concussion. This suggests the

necessity of paying closer attention to HRV levels as a non-invasive tool for assessing autonomic

function in concussed individuals. Interesting research involving athletes suggests that even

after full return-to-play (RTP), autonomic dysfunction may be present, as indicated by changes

in HRV. This means HRV monitoring could be insightful in determining whether someone is

ready or has fully recovered, beyond when symptoms clear up. Central autonomic syndrome is

believed to be the pathophysiology underlying this dichotomous state of sympathetic and

parasympathetic neuropathy, an imbalance that could cause hyperactivity or hypoactivity at

any given time. These regions regulate autonomic balance, and their impairment can lead to

heightened sympathetic response with dampened parasympathetic activity. Similar alterations

are consistently observed in HRV parameters of concussed individuals and are linked to various

physiological and cognitive symptoms, emphasizing the need for comprehensive autonomic

analysis when managing concussions.

HRV AND ITS USE IN CONCUSSION MONITORING

HRV provides a novel, non-invasive approach to evaluate autonomic function and the healing

process of patients diagnosed with concussions. HRV has been widely studied as a monitoring

tool, particularly in the context of sports-related concussions. Concussion research commonly

focuses on athletes due to their increased risk of sustaining concussions through sports-related

activities. Research has shown that HRV changes significantly during the course of concussion

recovery. For example, during the acute symptomatic phase, concussed patients

characteristically exhibit increased low-frequency (LF) power—reflecting heightened

sympathetic activity—and decreased high-frequency (HF) power—reflecting reduced

parasympathetic activity. Importantly, these HRV alterations may last even after the patients

feel symptomatically better. One study investigated HRV during symptomatic, asymptomatic,

and one-week post-return-to-play (RTP) phases of recovery. The findings suggested a

prolonged period of autonomic imbalance after symptom resolution, with elevated LF power

and attenuated HF persisting through the later stages of recovery. This indicates HRV's

potential as an objective measure of autonomic alterations associated with the chronic effects

of concussion, aiding in a more personalized understanding and tracking of recovery. This is

especially significant as HRV could serve as a biomarker for concussion management, avoiding

the limitations that traditional symptom-based assessments often encounter. While symptoms

such as headaches, dizziness, and cognitive impairment are critical indicators of concussion,

they might not represent the full scope of autonomic dysfunction. Measuring HRV provides a

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Avdeev, W. (2024). A Review of the Cardiovascular Consequences of Concussion and Mild Traumatic Brain Injury. British Journal of Healthcare and

Medical Research, Vol - 11(5). 65-68.

URL: http://dx.doi.org/10.14738/bjhmr.115.17614.

more holistic method of monitoring and can reveal foundational changes in the autonomic

system, helping clinicians make better decisions about when an individual is ready to resume

physical activity.

HRV BIOFEEDBACK-BASED INTERVENTIONS

Because concussions disrupt HRV, biofeedback interventions targeting HRV have emerged as a

promising approach for restoring autonomic balance and enhancing cognitive function within

a rehabilitation setting. HRV biofeedback teaches patients how to voluntarily affect their own

HRV through techniques like breathing exercises, relaxation methods, and mindfulness

practices. HRV biofeedback helps achieve this by improving parasympathetic activity and

reducing sympathetic dominance—essential elements of health maintenance and recovery.

Promising research has been conducted on the effects of HRV biofeedback in individuals with a

history of concussions. For example, specific resonant frequency training biofeedback has been

shown to improve HRV and decrease symptoms of post-concussion syndrome (PCS). Some

protocols involve visual or auditory biofeedback to assist users in reaching desired HRV levels,

which are purportedly associated with improvements in neurocognitive function, emotional

regulation, and overall quality of life. Furthermore, case reports have shown that HRV

biofeedback can be beneficial as an adjunctive treatment in post-concussion recovery. In one

case, a patient with multiple PCS symptoms, common among concussed athletes, completed a

10-week HRV biofeedback protocol, resulting in improved HRV metrics, decreased frequency

and severity of post-concussion headaches, and improvement or resolution of many other PCS

symptoms. These results suggest HRV biofeedback may represent a useful, non-invasive, and

cost-effective technique to support the recovery of individuals with concussions.

IMPORTANCE OF STANDARDIZED MEASUREMENT PROTOCOLS

To fully realize the potential of HRV in monitoring concussion recovery, standardized protocols

are essential. HRV measures can be inconsistent over short periods, affected by factors such as

posture, respiratory patterns, timing of measurements, or environmental conditions. Without

adequate standardization, HRV assessments remain vulnerable to issues related to reliability

and validity, potentially introducing variability in findings across different laboratories.

Standardized protocols will not only improve the accuracy of HRV measurements but also allow

for better data comparison across studies. If HRV is measured consistently, findings would be

more generalizable, advancing the use of HRV monitoring in clinical practice. This, in turn, could

enhance the precision of concussion management strategies and enable clinicians to make

better decisions about the timing of return-to-play and other critical aspects of concussion care.

Because HRV is a complex, non-stationary signal affected by multiple physiological, emotional,

or environmental factors, the conditions under which an HRV assessment is performed should

always be controlled. For example, measurements should be taken at the same time of day, in a

standardized posture and environment, to minimize external influences. Standardization is

particularly important to ensure HRV data accurately reflect the individual's autonomic

function and are not confounded by external variables.

CONCLUSION

The effects of concussions extend well beyond the brain, with significant impacts on

cardiovascular health due to changes in autonomic function, as revealed by HRV. The use of

HRV as a tool to monitor recovery and guide rehabilitation offers an exciting avenue for

improving outcomes in individuals with concussions. HRV biofeedback interventions hold