Vasovagal syncope is sudden fainting caused by a drop in heart rate and blood pressure when your body overreacts to certain emotional or neurologic triggers.
What is vasovagal syncope?
Vasovagal syncope is sudden fainting caused by a sudden drop in heart rate and blood pressure when your body overreacts to certain emotional or neurologic triggers. A loss of consciousness occurs due to reduced blood flow to the brain.
Those with vasovagal syncope will also experience certain skin, vision, circulatory, and other associated symptoms. These may include pale skin or the sensation of breaking out in a cold sweat, dilated pupils, tunnel vision or blurred vision, a slow or weak pulse, lightheadedness, frequent yawning, headache, nausea, and feeling hot or overheated with no clear cause.
Vasovagal syncope is not usually harmful or indicative of a more serious condition. Treatments include rest, the implant of a pacemaker, dietary changes, avoiding triggers, and maintaining good circulation in the lower body.
You do not need immediate treatment for this condition, as it is normal and not a cause for concern. However, since it has been going on for a while, you may want to discuss the fainting episodes with your doctor over the phone to discuss if any intervention is needed. You may require medical attention if during the fainting episode you fell and injured a body part.
Vasovagal syncope symptoms
Before fainting occurs, the following indicators of vasovagal syncope may be present, which can be defined by skin, vision, and circulation-related symptoms as well as a few others.
Skin-related symptoms that may occur include:
- Appearing pale, gray, or ashen
- Breaking out in a cold sweat
Vision-related symptoms of vasovagal syncope include:
- Dilated pupils
- Blurred vision
- Fading vision: This phenomenon is also called "graying out," meaning that vision fades away except for a small area directly in front of you. This is also called "tunnel vision."
Some circulatory symptoms may occur, including:
- Slow, weak pulse: Your pulse may be difficult to detect.
- Feeling lightheaded or dizzy: This is from the drop in blood pressure.
- Yawning: This is due to the lack of oxygen in the blood.
Other symptoms may include:
- Feeling hot or overheated: This may occur even in a cool place.
Causes of vasovagal syncope
Vasovagal syncope can be caused by emotional distress, bodily stress or sudden changes, other forms of stress, or heart conditions that can take a toll on the body.
Experiencing emotional shock and distress can cause an overreaction of the vagus nerve function and lead to fainting. Research has been completed to suggest the origin of this condition from an evolutionary standpoint. Examples include:
- Receiving tragic news
- Witnessing something gory or terrifying
- Seeing blood or having blood drawn
Bodily stress or sudden changes
Certain stressors that directly affect the body or sudden outside changes that can cause syncope include:
- General bodily stress: Sometimes the body can be so overwhelmed by physical stress that fainting results.
- Heat exhaustion: Heat exhaustion is another cause of dilated blood vessels and slow pulse.
- Dehydration: Dehydration causes a drop in blood pressure due to the loss of blood volume.
- Low blood sugar: This can induce vasovagal syncope due to a lack of energy for brain function.
- Rapid environmental changes: Going straight to a cold room, immediately sitting down, or even standing still can bring on syncope. The body simply cannot adjust to so many sudden changes in rapid succession.
Other forms of stress
Other forms of stress that can affect the body include:
- Standing for long periods of time: This can result in blood pooling in the feet and lower legs and not getting to the brain.
- Severe pain: This usually involves significant physical and emotional stress all at once.
- Urination/bowel movement: More rarely, vasovagal syncope can occur after urinating or having a bowel movement.
Due to poor circulation, heart conditions can result in insufficient blood supply to the brain and can cause syncope. Heart conditions that may cause syncope include:
- Bradycardia: An abnormally slow pulse
- Tachycardia:An abnormally fast pulse
- Arrhythmia: An irregular pulse
- Blockage: Any blockage in the veins and arteries can be a cause
- Plaque buildup: This occurs within the blood vessels.
- A clot: These form in the blood vessels, and possibly those within the brain.
Who is most likely to be affected
Vasovagal syncope is most common in people who:
- Are men
- Are over age 60
- Have low blood pressure
- Have a heart condition
- Have circulatory disease
- Have a family history of heart disease: Or sudden cardiac death
How vasovagal syncope occurs
The nerve normally responsible for controlling and coordinating the heartbeat and the dilation of the blood vessels is called the vagus nerve. The vagus nerve is actually a complex bundle of nerves running from the brain down into the abdomen.
- Blood pressure drops: When blood vessels dilatethey become larger and more open. This causes the blood pressure to drop much like the way water pressure would drop if water was suddenly flowing through a larger hose.
- The pulse rate slows: Due to the disturbance in the vagus nerve control, the pulse rate slows. This combination of low blood pressure and low pulse rate causes the blood to pool in the legs instead of going to the brain.
- Fainting quickly results
Why vasovagal syncope occurs
Vasovagal syncope is the most common type of syncope. Sudden fainting can actually have a protective effect because there is no organ more important than the brain. No other part of the body can function without it.
- To prevent oxygen starvation: If there is a severe drop in blood pressure for any reason, the brain can be quickly starved of oxygen and nutrients and begin to die.
- To maintain the blood supply: The vasovagal reflex causes a brief loss of consciousness and forces you to fall to the ground. This gets the head down on the same level as the feet, which helps maintain the blood supply to the brain so that it will survive.
What is the vasovagal reflex?
The vasovagal reflex is a related cause, and means that something has affected the vagus nerve causing a fast drop in both heart rate and blood pressure. This results in a sudden loss of blood flow to the brain, which leads to equally sudden unconsciousness.
Treatment options and prevention for vasovagal syncope
Vasovagal syncope is usually an acute condition, meaning it is a one-time incident with no lasting effects. Although this a harmless condition in itself, associated harm that can occur due to sudden falls is cause for concern. Treatments include rest, a possible pacemaker, and the avoidance of certain triggers.
The following treatments are likely for vasovagal syncope.
- Rest: In most cases, the condition of vasovagal syncope can be treated simply with rest and by allowing at least an hour or so for recovery.
- Pacemaker: If the cause turns out to be an irregular heartbeat, a pacemaker can sometimes correct the heartbeat and prevent any further episodes of syncope.
You should try to avoid the things that commonly trigger fainting as much as possible, including:
- Heat exhaustion
- Low blood sugar
- Prolonged standing
- Severe emotional distress
Vasovagal syncope can possibly be prevented by following certain protocol, such as:
- Quickly getting more blood flow to the brain: If you feel that you might faint, you can try to prevent it by quickly getting more blood flow to the brain. If you are standing, tighten the muscles of the legs to help force the blood upward to the brain. You should also try to lie down with your feet resting higher than your head. If you cannot lie down, you can sit down and place your head low between your knees.
- Dietary changes and prescription medications: You should try to moderately consume more salt and electrolytes as well as drink more water to keep your blood volume up. You can also discuss medications with your medical provider.
- Keeping blood from pooling in the feet and lower legs: You should wear compression stockings and avoid standing for long periods of time. If you feel lightheaded, you can tighten the muscles of your legs.
A one-time occurrence of fainting should clear up very quickly. However, you should not try to stand for at least an hour or so after regaining consciousness. The body needs time to regain its normal state and you may faint again if you try to get up too quickly.
When to seek further consultation for vasovagal syncope
You should seek medical attention if your fainting becomes a frequent occurrence or if you lose consciousness for a prolonged period and there is no obvious cause.
If fainting occurs more than once
If this is not the first occurrence of fainting you should see your medical provider to rule out any illness involving the brain, heart, or circulatory system. These may include tumors, heart arrhythmias, or blockage of the arteries. Fainting or severe lightheadedness that happens during exercise can be a serious warning sign, especially if there is a family history of sudden cardiac death.
If you hit your head or lose consciousness
The primary hazard of fainting is the chance of striking your head against a wall, a piece of furniture, or other solid object as you fall. Contrary to what's seen in the movies, a fainting person does not usually sink gracefully to the floor but tends to topple like a falling tree. A brief loss of consciousness is not harmful in itself, but a blow to the head during an unconscious fall can be very dangerous.
If there is no obvious cause
An episode of fainting that has an obvious cause, such as heat exhaustion, is probably not serious as long as it does not happen again and there are no other symptoms of heart disease or circulatory illness. If there was no significant bodily stress or a key moment prior to fainting, you should consult your physician.
Questions your doctor may ask to determine vasovagal syncope
- How long were you unconscious?
- Were you confused and disoriented when you woke up?
- Place two fingers under your jaw, as shown in the image. How is the rhythm of the heartbeat?
- Do you sometimes stare off into space with no recollection of doing so?
- After you woke up, did your muscles feel weak?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
Janeen has worked over eight years as a full-time medical transcriptionist, specializing in pain management and gynecologic oncology. She later began transcribing reports for hospital emergency rooms and acute care admissions. This background gave her a strong medical vocabulary as well as a heart for making medical information accessible to the average person, leading her to work as a medical writer. She began as a pre-veterinary medicine major at Texas State University.
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