Prescyncope is when you feel as if you’re about to pass out, but you don’t actually faint. It’s sometimes referred to as near syncope. You may also feel lightheaded, sweaty, nauseous, warm, and weak, or have a fast heartbeat or blurry vision.
Presyncope can be caused by the same factors that cause syncope. Syncope is when you actually pass out and later regain consciousness. Some of these factors are harmless, but others can be dangerous or even life-threatening.
What Causes Presyncope?
Presyncope happens when your brain temporarily receives less blood than usual. Many medical conditions can cause presyncope. Presyncope can be one of the following types.
Vasovagal
This type of presyncope is caused by a drop in blood flow to your brain due to low blood pressure. This is the most common cause of syncope and presyncope. It’s usually caused by a combination of being dehydrated and standing or sitting up too quickly. Vasovagal presyncope can also have emotional triggers, such as:
- Getting a shot (an injection)
- Having blood drawn
- Seeing blood
- Standing up too quickly
- Standing for too long
- Unexpected trauma, pain, or stress
Situational presyncope is another type of vasovagal presyncope. This occurs when you have a reflex response to a specific trigger. Your heart may slow, or your blood vessels may widen. This causes a drop in your blood pressure, lessening blood flow to your brain. Some other situational triggers can include:
- Dehydration
- Fear
- Hunger
- Peeing (called post-micturition presyncope)
- Eating
- Lifting something heavy
Orthostatic hypotension
This is also a type of vasovagal syncope or presyncope. When you stand, your blood vessels narrow to keep blood from collecting in your legs. This doesn’t happen in people with orthostatic hypotension, causing a drop in blood pressure when they stand, which can cause presyncope.
Cardiac
If your heart beats too fast, this is called tachycardia. If it beats too slowly, this is called bradycardia. Both can cause presyncope or syncope. Other types of heart arrhythmias, or abnormal rhythms, can also cause presyncope.
Cardiac presyncope or syncope can be caused by problems with a pacemaker. They might also indicate a tear in the large artery that carries blood to the rest of your body. A narrowing of the valve between your aorta and heart might also cause you to feel faint.
Neurologic
Neurologic presyncope can be caused by conditions such as a stroke or seizure. It can also result from a transient ischemic attack (TIA), which is a brief stroke that only lasts a few minutes. Other, less common causes of neurologic presyncope include migraine and normal pressure hydrocephalus (NPH), which is a type of brain disorder.
Postural orthostatic tachycardia syndrome (POTS)
This is a rare disorder that affects your blood flow. It most commonly occurs in women between the ages of 13 and 50. It happens when your heart rate speeds up by at least 30 beats per minute when you stand. It causes other symptoms when you stand, such as presyncope and tiredness. POTS can also cause palpitations — when your heart feels like it’s beating too hard or too fast.
How Common Is Presyncope?
It’s hard to know how common presyncope is because information about it is not usually included in reports of syncope. Presyncope is likely more common than syncope. About 19% of people in the United States will experience an episode of syncope in their lifetime. Also:
- 58% of people who experience syncope are women.
- 3% of emergency department visits are for syncope.
- 6% of hospitalizations are from syncope.
- Most episodes of syncope occur either in early adulthood or after the age of 70.
One study that focused on presyncope showed that:
- The average age of patients was 56.
- 61% of patients were women.
- 49% of patients with presyncope were admitted to the hospital, compared with 69% of syncopal patients.
- 20% of patients required medical help or had an adverse outcome.
What Can I Expect if I Have Presyncope?
You’ll feel like you’re about to pass out, but you won’t lose consciousness, says Hem Bhardwaj, MD. She’s Vice-Chair for Operations and Quality for Cardiology at VCU Health Pauley Heart Center in Richmond, Virginia.
“People often describe it as lightheadedness, dizziness, or a feeling of weakness,” she says. “Presyncope may also be accompanied by nausea, sweating, or heart palpitations.”
Your health care provider will try to trace presyncope to an underlying cause, such as:
- Dehydration
- Low blood sugar
- Anemia
- Certain types of infections
- Reflex responses (such as vasovagal episodes)
- Certain medications
- Abnormal heart rhythms
- Heart valve disease
- Vascular disease affecting blood flow to the brain
How Is Presyncope Diagnosed?
It’s important to talk to your doctor if you have presyncope symptoms to rule out a serious condition. Your doctor will listen to your symptoms and do a physical exam. You may need other tests as well, which could include:
- Tilt table test, which measures your blood pressure and heart rate at various positions, from lying flat to upright on a special table
- EKG, which measures the electrical rhythm of your heart
- Exercise stress test, which is an EKG done while you’re doing intense exercise
- Echocardiogram, which is an ultrasound of the heart
- Electrophysiology study, which is a test used to diagnose problems with your heart’s rhythm
- Holter monitor, which is a vest that you wear that continuously records your heart rhythm over one to seven days
- Event monitor, which is an EKG device that you wear for one to two months
Can Presyncope Be Prevented?
The feeling of “I almost passed out” can be uncomfortable and scary, says Srihari Naidu, MD, professor of medicine at New York Medical College. Depending on the cause of presyncope, you might be able to prevent it from happening, though.
“If it’s due to a typical fainting spell, something we call vasovagal or neurocardiogenic syncope, then maintaining adequate hydration and avoiding standing for prolonged periods of time will usually avoid presyncope,” says Naidu. “However, if it’s due to arrhythmia, such as fast or slow heart rhythms, then it may not be able to be prevented without medications or procedures. And finally, the same thing goes for valve or heart muscle problems, in which usually fixing the valve is needed to prevent the presyncope.”
If blood pressure medications are causing presyncope, adjusting the dose may help, Bhardwaj notes. “In people with diabetes, episodes related to low blood sugar may improve with changes to meal timing or adjustments to their diabetes medications, or both.”
Your age also can be a factor. For example, vasovagal presyncope is more common in people younger than 40. Vasovagal presyncope “is a body reflex, and as with all reflexes, it is stronger in youth,” Naidu says. “So most people who faint by seeing blood, for example, usually grow out of it over time.”
When Should I See My Health Care Provider About Presyncope?
While you should always see a doctor if you have an episode of presyncope, if you have it frequently or can’t trace it to a simple cause, it’s a must.
“If you’ve experienced presyncope, it’s helpful to note the details surrounding the episode, such as what you were doing at the time, any warning symptoms, and whether it has happened before,” Bhardwaj says. “Sharing this information with your healthcare provider can help them make a more accurate diagnosis. Understanding why your presyncope occurred is especially important if symptoms return in the future, and can help you feel more confident managing those presyncope symptoms.”
What Questions Should I Ask My Doctor?
Helpful questions to ask your health care provider include:
- What caused the presyncope?
- Do I need any blood work or additional testing?
- Could my medications have contributed to the episode?
- Are there warning signs I should watch for in the future?
- What steps can I take to prevent this from happening again?
- Is it safe for me to work as usual, exercise, and/or drive?
- When should I follow up with you?
You also might ask about simple measures that can help prevent presyncope, such as compression stockings, hydration, and avoiding prolonged standing in one place, Naidu suggests.
What Are the Risk Factors for Presyncope?
Common risk factors for presyncope include:
- Dehydration
- Sudden changes in position (such as standing up quickly)
- Certain medications
- Heat exposure
- Low blood sugar
- Low blood counts
- Recent illness, such as infection or fever
- Skipping meals, which can cause a dip in blood sugar
- Stress, which can trigger a reflex response
- Heart conditions such as valvular disease or abnormal heart rhythms
- Vascular disease affecting blood flow to the brain
How Is Presyncope Treated?
The treatment for presyncope will depend on the cause and may include:
- Being careful when you stand up
- Raising the head of your bed while you’re sleeping
- Medications
- Stopping or changing existing medications
- Avoiding the situations that cause your presyncope
- Treating any heart conditions you may have
- A pacemaker, if needed
- Wearing compression stockings to help your circulation
- Changing your diet, which may mean consuming more salt or potassium, eating smaller meals more frequently, drinking more fluids, or avoiding caffeine and alcohol
Takeaways
Presyncope happens when you feel like you’re about to faint or pass out, but don’t.
The causes can widely vary – from standing up too fast, to a clash with meds you’re taking, to an abnormal heart rhythm. There are many ways to guard against it.
If you do have an episode of presyncope, even if you think it was triggered by something simple like dehydration, it’s a good idea to check in with your doctor. If it happens regularly, a visit to your health provider is a must.
Presyncope FAQs
What deficiencies cause presyncope?
Deficiencies that may contribute to presyncope include iron deficiency and electrolyte imbalances such as low potassium or low magnesium levels, says Bhardwaj. Low blood sugar (also called hypoglycemia), though not a vitamin deficiency, can also lead to presyncope.
What exercises are good for presyncope?
“In general, leg exercises to maintain good muscle strength, and cardiovascular exercise to maintain good reflexes, will assist in preventing presyncope and syncope,” says Naidu. The most important aspect of physical activity is maintaining proper hydration and avoiding dehydrating drinks with caffeine or alcohol.
Can anxiety cause syncope?
“In some cases, extreme anxiety can trigger the same reflexes that cause an abnormal drop in blood pressure, and therefore trigger the vasovagal presyncope or syncope,” Naidu says. “This is what happens when people see blood or some other trigger, and it sets off a cycle where the heart beats harder and faster, you feel warm, and then the blood pressure drops.
Because this happens slowly, he advises, pay attention to these warning signs. Lie down for about five minutes until it passes.
