Blackouts (Syncope): Causes and Diagnostic Tests and When to See a Doctor

Blackout, medically called syncope, affects many people and about half of the population in the UK experience at least one blackout in their lifetime. In most cases, blackouts do not result from harmful causes and occur once. However, some people experiencing blackouts need further tests as some causes of blackouts are harmful.

What is a blackout (syncope)?

Syncope is a short episode where a person becomes unconscious for no more than a few minutes and recovers fully.

Possible causes of syncope unrelated to the heart

A common cause of a blackout is a fainting episode, also called vasovagal episodes. This occurs when the pulse or blood pressure falls for a short while as a kind of reflex. This usually happens:

• When you’ve been standing for an extended time on a hot day, or you are dehydrated
• As a reaction to fear or pain. It is more common during blood sample collection for blood tests

Causes of syncope related to the heart

About 15%of blackout cases result from a heart problem. Possible heart issues related to syncope include:

• Increased and abnormal heart rate (arrhythmia)
• Slow heart rate (heart block or bradycardia)
• Structural heart problems such as a narrowed heart valve

When does a blackout require emergency attention?

If a blackout results from an underlying heart issue such as slowed, increased or abnormal heart rate, it requires immediate attention. If you have a blackout episode, ensure you visit your doctor to seek medical care and advice.

Your health specialist will assess the chances of the blackout resulting from a severe medical issue and determine whether you need further investigation and treatment.

Diagnostic tests

The following are common diagnostic tests for blackouts;

• Echocardiogram

An echocardiogram is a heart ultrasound scan checking the heart’s function and structure. It helps determine if there is a problem with the valves in the heart.

• More advanced tests

Some people may need more advanced tests, such as loop recorder implants to diagnose the cause of blackouts. A loop recorder is a small device inserted under the skin in the chest area to monitor the heart rate for a few weeks or years. This extended heart monitoring allows the detection of heart rhythm irregularities that an echocardiogram or electrocardiogram may miss.

The tilt test is also an advanced test for diagnosing the cause of blackouts. You will lie on a table that gradually moves your body from a horizontal to a vertical position during the tilt test. This test aims at simulating the feeling of standing up and checking if the brain sends unusual signals that cause blackouts.

Blackout treatments

If the cause of your blackouts is simple faints (vasovagal episodes), the following simple measures can prevent the blackouts;

Lying or sitting down when you feel you are about to have an episode to avoid collapsing

Increasing intake of fluids ensures you remain hydrated, especially on hot days or when you stand for long periods

Clenching your muscles if you feel a blackout episode coming on can increase your blood pressure to prevent the attack from occurring

If your blackouts occur due to an underlying heart condition, you need to visit your healthcare provider to treat the disease. If the blackouts are due to bradycardia or slow heart rhythm, you may need a pacemaker implant. Blackouts resulting from a slow heart rhythm is rare in people below 50 years, but the risk increases with age.

If you have frequent blackouts, ensure you see a private doctor near you for diagnosis and treatment if necessary.