DISCLAIMER: All information contained on these pages is intended for Canadian residents only and is NOT intended as specific medical advice for any individual with a medical condition similar to that described herein.


Syncope (Blackouts) Syncope (sink oh pee) is defined as a transient loss of consciousness with spontaneous resolution. The terms that are used most often to describe syncope are fainting, blackouts or dizziness. Pre-syncope is the feeling of imminent loss of consciousness. It often precedes loss of consciousness, or may occur on its own without frank syncope.

Blackouts have a host of different causes, which may be anything from cardiovascular causes to neurological causes to psychiatric causes. The vast majority of episodes have cardiovascular causes. The most frequent diagnosis is vasovagal syncope. If you have received a diagnosis of vasovagal syncope from your doctor, please refer to the Vasovagal Syncope section.

A doctor determines the cause of blackouts after a clinical assessment in conjunction with preliminary testing in 50% of patients. An additional 30% of patients will be diagnosed after further testing. In at least 20% of patients, no cause is ever determined because blackouts resolve. Most patients with a single blackout will not have a recurrent blackout. Having said this, many patients are referred to a cardiologist because they have had more than one blackout.

Cardiac testing that is performed in blackout patients often includes an echocardiogram to assess the structure of the heart, as well as various monitoring tests to assess the rhythm of the heart. When vasovagal syncope is considered, a tilt table test may be performed.

The challenge in diagnosing patients with unexplained syncope stems from the fact that the cause has resolved by the time the patient presents for medical attention. For this reason, the heart's rhythm and the blood pressure and the brain's function is often restored to normal by the time these parameters are checked in the emergency room or in the physician's office. This leads to several forms of testing to try to assess the likelihood of recurrence, to set up a long term monitoring strategy to try to "capture" the next episode, or to provoke the symptoms with special testing.

The most frequently performed tests involve monitoring of the heart or brain to see whether ongoing abnormalities explain the syncope. These include a simple 12-lead EKG, a 24 or 48 hour Holter monitor, and an electroencephalogram (EEG). These monitor heart and brain function to look for evidence of heart slowing or racing, or abnormal brain function that could explain an arrhythmia or seizure.


Additional monitoring tests include use of an external or implanted loop recorder (pictured here) that

provides long-term cardiac monitoring to correlate arrhythmia with recurrence of symptoms. The first monitoring test that is often performed is a Holter monitor that continuously records the hearts rhythm for 24-48 hours.     The second form of monitor is a telephone or rhythm transmitter that is applied to the chest wall for 1 minute, recording a basic EKG during symptoms. The stored EKG can usually be sent to the recording center by phone line like a fax.


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