Common causes also include dehydration, standing too long, or intense pain.
Avasovagalresponse involves stimulation of the vagal nerve.
If stimulated, it can cause a sudden drop in heart rate, blood pressure, and other symptoms.
Illustration by Jessica Olah for Verywell Health
The vasovagal reflex is not necessarily abnormal, and the nerve pathways involved are most likely present in everyone.
However, finding no specific cause for the episode is not uncommon.
How It Works
The vasovagal response is also referred to as vasovagal syncope.
During an episode, the vasovagal nerve is overstimulated.
Overstimulation can occur due to fear (e.g., when donating blood), dehydration, or other causes.
Once stimulated, heart rate and cardiac output decrease.
Additionally, blood vessels may also widen in a process known as vasodilation.
This decreases blood pressure and reduces blood flow to the brain, causing feelings of lightheadedness or syncope.
There’s increasing evidence for the vagus nerve’s role in digestion and connections with the brain and heart.
Vasovagal syncope is sometimes called a neurocardiogenic response.
If the vagus nerve is suddenly stimulated, the reflex response is automatic.
Immediate messages are sent to the brain, affecting central and peripheralnervous systemsand thecardiovascular system.
The most common symptom of a vasovagal response is dizziness and lightheadedness without losing consciousness.
If you do lose consciousness, you usually recover quickly.
Vasovagal symptoms can sometimes be because of another health condition.
Tell your healthcare provider if you experience them so you’re free to get a proper evaluation.
Cardiac pacing is invasive and reserved for patients whose quality of life is severely negatively impacted by fainting episodes.
Aganglionablation is less invasive and can help reduce the body’sbradycardiaresponse (slow heart rate).
Most cases of vasovagal reflex and syncope are benign.
The biggest risk is falling.
If you experience an injury from falling, seek medical care.
Prevention
When you begin experiencing the signs of syncope, you might take several measures.
If stress is a trigger, keep yourself as calm as possible.
Check for injuries and see a healthcare provider if needed.
When to See a Healthcare Practitioner
Fainting usually isn’t an emergency.
Summary
The vasovagal response is a common cause of fainting.
The vagus nerve is connected to the heart and blood vessels.
If it is triggered, it can lower your blood pressure and heart rate and make you feel faint.
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