Types of syncope and the triggers

Written by: Dr Mashkur Khan
Published: | Updated: 19/11/2020
Edited by: Robert Smith

Syncope is a medical term used to describe a faint or blackout that is due to a sudden drop in the supply of blood to the brain, leading to a short-term loss of consciousness.

man with syncope

Dr Mashkur Khan is a leading specialist in general internal medicine. We got in contact with him recently to find out about the different types of syncope, what their main triggers are and how the condition is diagnosed.


What are the four types of syncope?

The four major types of syncope are the following:

  • Neurocardiogenic
  • Situational
  • Postural / orthostatic hypotension
  • Neurogenic

There are two other classifications based on the result of investigations:

Vasodepressor – when the blood pressure drops.

Cardioinhibitory – when the cardio drops down.

What are some of the main triggers of syncope?

Syncope is very sudden and unexpected it often occurs where the person is completely unaware. Common triggers can include:

  • Dehydration.
  • Sudden loss of consciousness from global cerebral hypoperfusion is a trigger. It’s a protective mechanism.
  • Medication, drug interaction - drugs that lower blood pressure, anti-hypertensive, drips for angina, any drugs that lower blood pressure.
  • Cardiovascular effects from giving blood, seeing something unsightly, sudden stress or anxiety, bad news.
  • Heart rhythm problems whether too fast or too slow, bradycardia, super trinocular cardiacia (when the heart rate goes up really rapidly).
  • Blood pressure dropping or changes
  • Valve disease, syncope, hypertrophic.
  • Certain change in posture, if you get up after an hour or two.
  • Alcohol consumption, it can make you dehydrated and it causes changes in body physiology, because of that it can make you more vulnerable to syncope.
  • Fractures or intense pain
  • Levels of carbohydrates
  • If you don’t have enough sugar it’s hypoglycaemia, that’s another cause.
  • If you wear a tight collar, collar, constrictions of receptors in neck, after coughing fits, chest infections, cannot stop coughing.
  • Constipation or straining in the bathroom.

How is syncope diagnosed?

More often than not syncope can be diagnosed through basic tests and specialist tests aren’t needed so much.

I do blood tests for anaemia, electrolyte imbalance, low sodium, low potassium, thyroid function and underactive thyroid as these can cause it.

If the heartbeat test is normal then you can rule out heart disease. Then of course we need to do a simple echocardiogram test to check for valve disease.

We would check for blood pressure, it’s a basic test but very important and it is done when a patient is laying and standing up. If you have postural syncope, this is extremely useful, a simple test can change the diagnosis. You lie the patient flat for 20 mins, then ask the patient to stand. Then we would check after two minutes, three minutes and then four minutes.

By the time patients see me, the GP would have done the basics and would have come to the conclusion that the patients have autonomic problems (difficulty walking) and/or blood pressure problems.

On patients, I perform the gold standard test. It’s is a head up tilt table test. We put the patient flat, then at 70 degrees. If the lower legs don’t work effectively use we would put your upper body to stay upright, that’s when you should check what happens to the blood pressure and pulse. 45-minute test will show slowing of heart of blood pressure changing.

If they don’t have that issue you induce a faint with a spray and then you can see what happens if blood pressure or blood beat changes.

Low risk group – they faint, the outlook is good, they can get on with their life.

Intermediate group – sudden change in physiology.

High risk – could happen anytime, you’re sitting, out shopping, when visiting family. Those are the people we should be careful about and who need treatment.

We also do prolonged heart rate monitoring, 72-hour tapes, a monitor for about 3 to 4 weeks to check the rhythm of the heart.

In Dr Mashkur Khan ’s next article, we will discuss treatment options. To have syncope treated effectively, we recommend getting in touch with him. Visit his Top Doctors profile today for information on appointment availability.

By Dr Mashkur Khan
Internal medicine

Dr Mashkur Khan is a leading London-based consultant physician, with a special interest in geriatric medicine and diseases common in the elderly population, such as dementia, Parkinson's disease and syncope.

From his main base at Nuffield Health Guildford Hospital, and his private clinics across Epsom, Weybridge, Guildford and New Malden, he provides clinical excellence in all aspects of general medicine. He is also the Dementia Lead at Epsom and St Helier University Hospitals NHS Trust.

Dr Khan deals with multi-system pathology and has vast experience in multi-system diseases which affect the quality of life of the patient, such as complex fainting and blackouts. He is also an expert in treating balance disorders and dizziness. 

Dr Khan is also considerably experienced in treating patients who present with an acute crisis, diagnostic dilemmas and atypical presentations. This could include unexplained weakness, weight loss or anaemia.

Alongside his clinical practice at the Nuffield Health Guildford Hospital, Dr Khan also devotes time to teaching and examining future doctors. He is an Honorary Senior Lecturer at St. George´s, University of London, as well as an examiner for the Membership of the Royal College of Physicians (MRCP) clinical examination, both in the UK and internationally.

Dr Khan has also been the District Tutor for the Royal Collge of Physicians at Epsom General Hospital, and a member of the Training Programme Board of the South West Sector London Deanery for Geriatric Medicine. He has given numerous lectures on syncope, and the possible causes of blackouts and loss of consciousness.  

He is an active member of a number of associations in his field, including the Royal Society of Medicine and the Movement Disorder Society, USA. He has previously held the position of Section President of the Royal Society of Medicine and currently sits on the Section Council.

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