If you suddenly felt light-headed and sweaty and then passed out while getting your blood drawn, you were experiencing what medical doctors call vasovagal syncope.
Vasovagal1 syncope is the most common reason for individuals to swoon or faint. It frequently happens in church or in response to severe emotional stress or pain. If you just felt very light-headed but didn’t lose consciousness completely, we call that near-syncope.
The skeptical cardiologist has seen lots of patients with vasovagal syncope (aka neurocardiogenic syncope) but surprisingly has never written about it for public consumption.
I recently saw a patient who had passed out in various situations, including blood-drawing. I provided her with the information on vasovagal syncope below, which, although generated by OpenEvidence is a great summary of the causes and symptoms, along with specific actions you can take if you start to feel light-headed to prevent completely passing out and long-term actions to prevent or minimize recurrence.
Vasovagal Syncope Instructions
Vasovagal syncope is a common cause of fainting. It happens when the body overreacts to certain triggers, causing the heart rate and blood pressure to drop suddenly. This can lead to a brief loss of consciousness. Vasovagal syncope is usually not dangerous, but it can cause falls or injuries, so it is important to know how to recognize and manage it.[1][2][3]
What are the symptoms?
– Warning signs (prodrome) may include:
– Lightheadedness or dizziness
– Nausea
– Sweating
– Feeling warm or flushed
– Blurred or tunnel vision
– Pale skin
– Weakness or fatigue after the event[1][4]
Common triggers:
– Standing for a long time
– Hot environments
– Emotional stress, pain, or the sight of blood
– Medical or dental procedures[1][2]
What should you do if you feel faint?
1.Get to a safe position: Sit or lie down right away. Lying down is best, with your legs raised if possible. This helps blood flow to the brain and can prevent a fall.[1][4]
2.Use physical counterpressure maneuvers (PCMs): If warning signs are present and you are able, try these techniques to help prevent fainting:
– Cross your legs and tense your leg, abdominal, and buttock muscles
– Squeeze a rubber ball or make a fist and tense your arm muscles
– Squat down if standing is unavoidable[1][5][4]
– These maneuvers can help raise blood pressure and may stop the faint from happening.
3.Stay down until you feel better: Do not try to stand up too quickly after an episode. Wait until you feel fully recovered.[1][4]
How can you prevent future episodes?
–Learn your triggers: Try to avoid situations that have caused fainting in the past, such as standing for long periods or being in hot places.[1][2]
–Stay hydrated: Drink plenty of fluids (about 2 to 3 liters per day, unless you have a medical reason not to). This helps keep blood pressure up.[2][5]
–Increase salt intake: If your doctor says it is safe, you may be advised to eat more salt (about 6 to 9 grams per day, or 1 to 2 teaspoons), unless you have high blood pressure, heart, or kidney problems.[2][5] (Adding electrolytes (like LMNT) to water or salt tablets can also boost sodium intake.)
–Compression stockings: Wearing compression stockings may help prevent blood from pooling in the legs.[2][6]
–Physical activity: Gentle exercise and certain yoga maneuvers (such as Tadasana) may help reduce episodes in some people.[6]
When to seek further help:2
– If fainting occurs often or causes injuries
– If fainting happens without warning or during exercise
– If there is chest pain, palpitations, or shortness of breath with fainting
– If there is a family history of heart problems
Medications:
– Most people do not need medication (or pacemakers3.) If lifestyle changes are not enough and episodes continue, medications such as midodrine or fludrocortisone may be considered. These are only used in select cases and require careful monitoring.[1][2][3]
– Beta blockers may be considered in adults over 40 with frequent episodes, but are not routinely recommended.[3][5]
Key points:
– Vasovagal syncope is usually benign and not a sign of a serious problem.
– Recognizing warning signs and acting quickly can prevent injury.
– Most people can manage their symptoms with education, trigger avoidance, hydration, and simple maneuvers.[1][2][3][4][6]
Prodromally Yours,
-ACP
N.B.
1 The cause of vasovagal syncope is a reflex-mediated process characterized by sympathetic inhibition and parasympathetic activation, leading to an acute fall in blood pressure and heart rate. This results in transient global cerebral hypoperfusion and subsequent loss of consciousness. The reflex can be triggered by emotional, sensory, or hemodynamic stimuli such as the sight of blood, pain, prolonged standing, or dehydration. The prodromal phase involves autonomic activation (e.g., pallor, diaphoresis, nausea), followed by abrupt sympathetic withdrawal and a surge in epinephrine at the time of syncope.
2 A good PCP can make the diagnosis of vasovagal syncope or near-syncope on the basis of a detailed history (confirming a scenario that is classic) and exam (confirming no cardiovascular abnormalities (murmurs, rubs, etc.) and normal resting and orthostatic BP and heart rate.) It is reasonable to do an ECG. Referral to a cardiologist is common and reasonable for the 4 reasons listed under “when to seek further help.” Once you have entered a cardiologist’s office the sky is the limit on what additional testing will be performed and will be determined by which of those 4 reasons is present, whether there are any features suggesting cardiac disease or arrhythmia, and unfortunately , testing available in the office. I’ll try to give a more complete guide to cardiac testing in the patient with syncope down the line.
3 If you are referred to an EP cardiologist for vasovagal syncope who recommends a pacemaker strongly consider a second opinion
References
- 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Shen WK, Sheldon RS, Benditt DG, et al. Heart Rhythm. 2017;14(8):e155-e217. doi:10.1016/j.hrthm.2017.03.004.
- Management of Vasovagal Syncope. Ballantyne BA, Letourneau-Shesaf S, Raj SR. Autonomic Neuroscience : Basic & Clinical. 2021;236:102904. doi:10.1016/j.autneu.2021.102904.
- 2015 Heart Rhythm Society Expert Consensus Statement on the Diagnosis and Treatment of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia, and Vasovagal Syncope. Sheldon RS, Grubb BP, Olshansky B, et al. Heart Rhythm. 2015;12(6):e41-63. doi:10.1016/j.hrthm.2015.03.029.
- 2019 American Heart Association and American Red Cross Focused Update for First Aid: Presyncope: An Update to the American Heart Association and American Red Cross Guidelines for First Aid. Charlton NP, Pellegrino JL, Kule A, et al. Circulation. 2019;140(24):e931-e938. doi:10.1161/CIR.0000000000000730.
- 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Shen WK, Sheldon RS, Benditt DG, et al. Journal of the American College of Cardiology. 2017;70(5):e39-e110. doi:10.1016/j.jacc.2017.03.003.
- Management of Patients With Reflex Vasovagal Syncope With a Protocol Involving a Yoga Maneuver Tadasana. Rao BH, Gowlikar V, Vooturi S, Raj JP, Surath M. International Journal of Cardiology. 2024;412:132302. doi:10.1016/j.ijcard.2024.132302.
3 thoughts on “Information for Patients on The Most Common Cardiac Cause of Fainting: Vasovagal Syncope”
I apparently don’t know how the comment section works. I did not finish my thought…
I was a 6’1″ 230+ lb Marine about 30 years ago (I am more than a Marine now, I’m a Marine plus 30 lbs or so…), and I was (still am) subject to Vasovagal Syncope.
I’d never heard the full medical term before today though; only the petite, female, Navy corpsman sighing loudly and stating to the Navy doctor standing over me saying, “He vagal’d himself, it’s always the big ones.”
This is precisely one of the topics I was going to ask about in my appointment next Monday with my electrophysiologist. Nothing worse than feeling light headed when I stand up, but still a bit of an inconvenience. Another topic I was going to bring up is related to a previous post on transesophageal echocardiography. I am fairly certain this was done before my first cardioversion less than a year ago. There were differences noted compared to my last echocardiogram. I really appreciate your contributions to my continuing medical education.
This happened to me many times in my younger years until I learned a helpful trick. Raising both my arms was often enough to avoid fainting until I could get somewhere to sit down. I learned this AFTER fainting at the gym urinal and woke up with my face in it (and a bloody lip from the impact.) Micturition syncope, a close cousin, is when you faint while urinating. Sometimes you can’t stop midstream to sit down, so this has saved me from repeating this embarrassing event. I also broke a friends toilet and a towel rack prior to learning this trick!!