About Careers MedBlog Contact us

What are the Causes of Fainting / Syncope

Last Updated on Aug 14, 2014
Font : A-A+

Causes of Fainting / Syncope

Causes of fainting could be reflex-mediated, cardiac, orthostatic or cerebrovascular.

Causes of syncope include:

  • Reflex-mediated Causes: Reflex-mediated syncope often occurs due to a failure with the normal reflexes to maintain blood supply to the brain with a change in posture. Types of reflex-mediated syncope are:
  • Vasovagal syncope: Vasovagal syncope is the common faint observed in many individuals. It is usually preceded by conditions like emotional stress, trauma, pain, sight of blood or prolonged standing. Initially, the patient experiences a prodrome phase. During this phase, the patient suffers from symptoms like excessive salivation, nausea and discomfort in the stomach, sudden tiredness, dizziness and yawning, which lasts for seconds to a few minutes. This is followed by the patient falling down. Following the syncope, the patient may experience confusion, disorientation and a feeling of being unwell.
  • Carotid sinus syncope: The carotid sinus is a bulb-like enlargement on the carotid artery, an artery that supplies to the brain. Stimulation of the carotid sinus with turning of the head, while shaving or wearing a tight collar, can result in syncope.
  • Situational syncope: Situational syncope is syncope that arises during certain situations like while passing urine, defecating or coughing.
  • Glossopharyngeal and trigeminal neuralgia: Inflammation affecting the Vth (trigeminal) and IX (glossopharyngeal) facial nerves can result in reflex-mediated syncope when these nerves are stimulated. These conditions are commonly associated with pain in the regions supplied by these nerves.
  • Cardiac Causes: Any condition affecting the heart could result in a decrease in blood supply to the brain, resulting in a syncopal attack. Some of the cardiac causes that could result in syncope are:
  • Mechanical or structural causes: Any condition that could affect the structure of the heart muscles, heart valves, pericardium or major arteries can result in syncope. Some of these conditions include valvular heart disease, heart attack, hypertension and congestive heart failure. The presence of these conditions may be known to the patient or may be diagnosed with ECG and other cardiac tests.
  • Arrhythmia: An arrhythmia is an abnormal heart rhythm, which could result in a disturbance in blood flow to the brain and thereby cause syncope. Drugs used to treat arrhythmia can also sometimes result in arrhythmias. Arrhythmias can be diagnosed on physical examination or continuous ECG monitoring.
  • Orthostatic Causes: Orthostatic syncope is a type of syncope that occurs due to sudden fall in blood pressure with change of position from lying or sitting to standing. It may be due to:
  • Primary causes: Neurological conditions like autonomic failure and Parkinsonís disease result in orthostatic syncope because of a failure of the nerves to adjust the blood pressure with standing position.
  • Secondary causes: Some underlying conditions can also result in orthostatic syncope. These include:
    • Reduced blood volume: Reduced blood volume due to dehydration or other conditions can result in orthostatic syncope. The heart rate is usually more than 100 beats per minute in these patients.
    • Medications and drugs: Some medications like those used for hypertension, depression and diuretics can result in orthostatic syncope. Illegal drugs as well as alcohol can also interfere with nerve function resulting in syncope.
    • Diabetes: Patients with diabetes may have abnormal nerve function, making them more prone to syncope.
  • Cerebrovascular Causes: Conditions interfering with the normal blood supply to the brain can result in fainting. Some of these conditions are:
  • Vertebrobasilar syncope: Reduced blood supply via the vertebrobasilar arteries to the brain can result in transient ischemic attacks and syncope. The patient may suffer from other symptoms like vertigo, headache, swaying while walking, difficulty with speech, double vision and sensory disturbances. Headache and dizziness during the recovery stage of a syncope should suggest vertebrobasilar insufficiency.
  • Vascular steal syndrome: Vascular steal syndrome like the subclavian steal syndrome is a consequence of reduced blood supply to the brain due to an obstruction or narrowing in a major artery like the subclavian artery. It may be diagnosed with arteriography or Doppler ultrasound.
  1. Miller TH, Kruse JE. Evaluation of Syncope. Am Fam Physician 2005;72:1492-500
  2. Benditt DG and Goldstein M. Fainting. Circulation. 2002;106:1048-1050

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Dr. Simi Paknikar. (2014, August 14). What are the Causes of Fainting / Syncope. Medindia. Retrieved on Feb 02, 2023 from https://www.medindia.net/symptoms/what-are-the-causes-of-fainting.htm.

  • MLA

    Dr. Simi Paknikar. "What are the Causes of Fainting / Syncope". Medindia. Feb 02, 2023. <https://www.medindia.net/symptoms/what-are-the-causes-of-fainting.htm>.

  • Chicago

    Dr. Simi Paknikar. "What are the Causes of Fainting / Syncope". Medindia. https://www.medindia.net/symptoms/what-are-the-causes-of-fainting.htm. (accessed Feb 02, 2023).

  • Harvard

    Dr. Simi Paknikar. 2021. What are the Causes of Fainting / Syncope. Medindia, viewed Feb 02, 2023, https://www.medindia.net/symptoms/what-are-the-causes-of-fainting.htm.

Post a Comment

Comments should be on the topic and should not be abusive. The editorial team reserves the right to review and moderate the comments posted on the site.

Recommended Reading
Health Topics A - Z
What's New on Medindia
How to Treat Hungover Skin
Blue Man Syndrome and Amiodarone
Quiz on Yeast Infection
View all

Medindia Newsletters Subscribe to our Free Newsletters!
Terms & Conditions and Privacy Policy.
This site uses cookies to deliver our services.By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Use  Ok, Got it. Close