Syncope, commonly known as fainting, refers to a sudden loss of consciousness, followed by a rapid and complete recovery. If dizziness or lightheadedness takes place without fainting, this is called presyncope.

A person with syncope recovers quickly, almost always without treatment. However, injuries occur in about 35 per cent of cases. Elderly people are more likely to be injured during a fainting attack.

Syncope is common; about one-third of people have a fainting event at some point in their life. In most cases, it is not a sign of a life-threatening problem, although in some patients, especially those with underlying cardiac disease, it could portend a risk of sudden death.

Syncope cause

To remain conscious, a supply of oxygen-rich blood must be pumped to the brain without interruption. If the brain is deprived of this blood supply, even for a brief period, passing out will occur.

Vasovagal syncope, or “common fainting”, is the most common type of syncope. A variety of conditions can trigger it, including physical or psychological stress (pain, fear, panic attack ...), prolonged standing or dehydration. In those instances, and in response to a heightened vagal nerve input and not to a heart problem in itself as the heart is usually normal in that case, heart rate slows dramatically and blood vessels expand causing blood pooling in the legs; both features result in low flow to the brain.

In other cases, vasovagal syncope is caused by an abnormal vagal response to activities such as urinating, having a bowel movement, swallowing or coughing. In still other cases, no trigger is identified.

In most cases of vasovagal syncope, you have some warning that you are near fainting, like dizziness, nausea, pale skin, “tunnel-like” vision and profuse sweating. After the event, some people feel very tired.

Orthostatic hypotension refers to low blood pressure that occurs when a person sits or stands up. Here, no heart slowing or excessive vessel dilatation occurs as in vasovagal spells. Causes include:

• Blood or fluid loss – reducing the amount of circulating blood, including to the brain.

• Alcohol and certain medications that can make the vessels “lazy” and not constrict in response to a change in body position, as normal. Example: blood pressure pills, psychiatry drugs and opiates.

• Illnesses that affect the nerves controlling vessels’ tone – Parkinson disease, diabetes mellitus ...

Heart rhythm problems

A number of disturbances in the rate and/or rhythm of the heart can cause syncope. These disturbances could result in a very slow or extremely fast heart beat.

Blockage of blood flow from the heart

The two most common causes are:

• Hypertrophic cardiomyopathy: an inherited condition in which areas of the heart muscle are thickened and cardiac chambers are “narrowed”. This interferes with blood flowing in and out of the heart, and could cause syncope.

• Severe aortic stenosis: the heart normally pumps blood through the aortic valve into the body’s largest artery or aorta, in order to supply blood to the brain and body. If the valve is tight (or “stenotic”), the flow to the brain is compromised, especially with effort, and fainting ensues.

Other causes

Less common causes of syncope include a heart attack, cardiac tumour, or blood clot in the lung arteries [“pulmonary embolism”].

Syncope diagnosis

It includes medical history, physical examination, and cardiac/neurological testing. Your doctor would decide which test(s) to run depending on the cause of syncope he/she suspects.

Syncope treatments

Vasovagal syncope treatment involves taking precautions to avoid potential triggers and minimise risk of harm. Example: if you faint while blood is being drawn, you may need to lie down during the procedure. Orthostatic syncope treatment:

• Use of elastic compression stockings

• Learning to stand slowly and in stages

• Regular exercises to keep muscles and vessels in tone

• Less alcohol and culprit medications

Medications, surgery, pacemakers and defibrillators are used to control syncope related to the other causes, mainly cardiac, mentioned above.

Safety issues

Passing out while driving can potentially harm both the patient and those around him/her. As a result, driving restrictions are sometimes recommended.

Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women’s Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients’ care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article.