Can spinal cord injury cause tachycardia?
Tachycardia is when you have a fast resting heart rate (over 100 beats per minute!).
While tachycardia is not very common amongst spinal cord injury patients, it can happen, and this article is going to explain why!
Tachycardia After Spinal Cord Injury
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Tachycardia is more common in people with spinal cord injury levels T6 and up.
Involuntary body functions like heart rate, body temperature regulation, and blood pressure are regulated by the autonomic nervous system.
The autonomic nervous system consists of 2 parts: the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system is responsible for your ‘fight or flight’ response. When activated, it increases functions like heart rate, alertness, and blood pressure.
In contrast, the parasympathetic nervous system is responsible for your ‘rest and digest’ response. When activated, it slows down your heart rate, stimulates digestion, and relaxes the blood vessels.
The sympathetic fibers that regulate heart rate are located around the T1-T5 levels of the spinal cord. The parasympathetic fibers align with the vagus nerve (which is not part of the spinal cord and branches off on its own).
When people have higher level spinal cord injuries, the sympathetic nervous system’s ability to regulate heart rate gets disrupted while the parasympathetic nervous system remains unaffected.
Why Tachycardia Occurs After Spinal Cord Injury
The majority of spinal cord injury patients actually experience bradycardia, which is when your heart rate is at or below 60 beats per minute.
When sympathetic response is disrupted, it cannot oppose parasympathetic response, and your heart rate drastically slows down.
So then what causes tachycardia after spinal cord injury? There are two possible reasons: 1) autonomic dysreflexia, and 2) as a complication when treating bradycardia.
The completeness of your spinal cord injury plays a significant role in determining how much your sympathetic nervous system is going to be affected.
The smaller the lesion, the fewer functions will be affected because there will be more spared neural pathways.
However, even the slightest lesion can disrupt communication between the brain and body, and signals between the brain and body can get miscommunicated.
Autonomic dysreflexia is when the autonomic nervous system overreacts when stimulated below your level of injury.
Rather than having heart rate slow down, your body may misunderstand and increase heart rate.
While bradycardia is a more characteristic side effect of autonomic dysreflexia, tachycardia can also occur.
Complications When Trying to Treat Bradycardia
Another way spinal cord injury patients can get tachycardia is as a complication of treating bradycardia.
Bradycardia treatment focuses on increasing heart rate. When the dose of that treatment is too high or your body acts adversely to it, your heart rate may increase too much, causing tachycardia.
The first line of treatment for bradycardia is usually atropine. It’s used to reduce vagal tone, which should lessen the harsh impact of the parasympathetic nervous system on heart rate.
Other treatments include the use of dopamine and epinephrine, which increase heart rate by stimulating the beta1 receptors in the heart.
Understanding Spinal Cord Injury and Tachycardia
If you’re experiencing tachycardia after spinal cord injury, it’s crucial to speak to your doctor and seek effective management.
Unmanaged tachycardia puts too much stress on the heart and significantly increases the chances of having a stroke or heart failure.
Symptoms of tachycardia include:
- Tightness in the chest
- Shortness of breath
Cardiac problems are a leading cause of death and other very serious complications after SCI, so don’t take tachycardia lightly.
Learning to identify and avoid things that can trigger autonomic dysreflexia like wearing tight clothes or having a full bladder can help you manage tachycardia.
Hopefully, this article helped you better understand why you might be experiencing tachycardia after spinal cord injury. Good luck!
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