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If you have passed out without a clear reason on a number of occasions you may have a heart condition causing this.  The commonest reason for someone passing out is a simple faint (also called a vaso-vagal syncope).  However other heart conditions can also cause fainting.  You may have a heart rate that becomes excessively slow, or excessively fast. 


Conditions that can cause fainting or blackout are:

  • Vaso-vagal syncope – another term for a simple faint this is the commonest reason for passing out and occurs due to a sudden drop in heart rate, blood pressure or a combination of the two.  Usually there is nothing wrong with your heart but it may be important to rule out a heart problem by having a number of tests for reassurance.

  • Bradycardia – this is the medical term for a slow pulse and can cause you to pass out.  Tablets such as beta-blockers can cause this but other heart conditions can also be responsible.  If you do have a number of blackouts due to a persistently slow pulse you may need a pacemaker to treat this.

  • Arrhythmia – very rarely heart rhythm problems causing a very rapid heart beat can also cause people to pass out. These conditions only usually occur in patients with pre-existing heart problems.


A number of tests can be undertaken to assess patients with fainting.

  • ECG – a simple 12 lead ECG is a heart tracing that can provide an indication of an underlying heart rhythm problem. It is a simple test that can be conducted in outpatients with the results available immediately. If the ECG is normal a heart problem may still be present but it is a simple and cheap test that can provide a lot of useful information.

  • Echocardiogram – an echocardiogram is also called a heart ultrasound test and is used to directly visualise the heart muscle and heart valves. It involves using a probe and some gel on the chest wall to view the heart on a screen. It is completely painless and helps determine how efficiently the heart is working. It can also provide information on the heart valves. The results are available immediately and this test is very useful to provide a quick diagnosis. It can also be useful in other conditions such as high blood pressure. The test is also useful if you have a heart murmur.

  • Ambulatory ECG monitoring – This is a portable ECG that a patient can wear up to 7 days and allows continuous monitoring of the patient’s ECG. Patients also get a diary so they can record the times of their symptoms. The ECG monitor is small (about the size of a mobile phone) with an activator button to press if the patient has symptoms. The ECG can then be analyzed and matched to the times in the diary to see if the symptoms (such as chest pains or palpitations) match any changes in the ECG pattern.

  • Implantable loop recorder procedure–  This is a small device that can be implanted under the skin in a minor surgical procedure. The device has the ability to monitor the heart rhythm continuously over a 3- year period. A patient with this device implanted will have a separate recording device to record their ECG when they have symptoms and download them to the hospital for their doctor to review. It offers an advantage over standard portable ECG monitoring in that it means the next time the patient has an episode of palpitations or fainting it can be monitored because the device is implanted into the patient.

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