What You Need to Know
This page was last updated: Tue, Nov 18, 2003
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 dizzy. Pre-syncope is the feeling of imminent loss of consciousness. It often precedes loss of consciousness, or may occur on its own without syncope. Many patients have "dizzy spells" that are not uncommon. Most people experience lightheadedness when they get up too quickly or if they are dehydrated. This is usually not of any consequence unless they also have episodes of actual loss of consciousness.
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 are caused by cardiovascular causes. The most frequent diagnosis is vasovagal syncope (see separate information section at Patient Info home page
A doctor determines the cause of blackouts after 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, and 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 brains 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 a certain problem recurring, or to provoke an abnormality that is felt to explain the blackouts.
The most frequently performed tests involve monitoring of the heart or brain to see whether ongoing abnormalities explain the syncope. These include 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 external or implanted loop records that provide 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.
The final form of monitor is a loop recorder. This device is worn continuously with 2 skin electrodes attached by a thin wire to a pager style device. This stores a longer ECG signal (typically 4-10 minutes), including the previous 3-9 minutes after the activation button is pressed, allowing event capture to take place even though symptoms have passed. The stored EKG can also be sent to the recording center by phone line like a fax.
An implanted loop recorder performs the same task as an external loop recorder, but does not involve any external hardware since it is inserted under the skin with a small operation . It records the heart's rhythm for 14 months, though it is only capable of storing 40 minutes of EKG.
The other major form of testing involves provocative testing. In this situation, tilt testing and electrophysiological testing is performed to try to induce a fainting episode or abnormal heart rhythm that would explain the episode of loss of consciousness.
Tilt testing is explained in the section called vasovagal syncope. Electrophysiological testing in the EP lab (see picture below) involves coming to the hospital for half a day. After receiving sedation through intravenous, the patient lays on an x-ray table. Local freezing is placed in the groin and shoulder area, and catheters are passed through the skin into the veins under the skin and into the heart. These catheters record the hearts electrical activity and speed up and slow down the heart to look for evidence of heart slowing or heart racing that may explain blackouts. This test is performed as a day procedure on an empty stomach without a general anesthetic. Patients incur a risk of 1/100 of minor complications, and 1/1000 of major complications. The risks and benefits of an electrophysiology study should be discussed with your doctor prior to proceeding.
Treatment of blackouts
Treatment of blackouts is dependent on the underlying cause. For patients with vasovagal syncope, lifestyle measures including increase in salt and water are often very successful. When an arrhythmia is diagnosed, treatment directed at the underlying cause is usually successful. For patients with heart slowing (bradycardia), a pacemaker is usually implanted. In patients with heart racing, medication is used or consideration of an ablation procedure or implantation of a defibrillator. Finally, in patients with less frequent causes, treatment is delivered based on special circumstances. One example of this would be treatment for epilepsy in patients where seizure explains their blackouts.
One of the most difficult situations surrounding blackouts is the impact on patient's lifestyles. This is particularly the case when it comes to impact on driving privileges. Driving privileges are governed by provincial or state law. It is important to be aware of the local laws and the impact on driving. In Ontario, current law states that after an episode of loss of consciousness, driving should be suspended for one month. If blackouts are recurrent (more than one within 12 months), driving is suspended for 12 months. In Ontario, a physician is obliged by law to provide the Ministry of Transportation with a medical report on any patient who has a condition that could make it unsafe to drive. For this reason, many patients are frustrated because they feel betrayed by the medical system for reporting them. Similarly, physicians feel that this law influences the doctor/patient confidentiality relationship in a negative way. Having said that, physicians are obliged to be law abiding in their reporting of patients. Once a diagnosis is obtained, patients can apply for re-instatement of driving privileges. A letter from the family doctor accompanied by any specialist information is often requested by the Ministry of Transport to allow them to review the file and render the decision about resumption of driving privileges. The principal of suspending driving privileges is based on the priority of protecting the safety of the public as well as the individual driver from the harm of driving. Canadian and Ontario physicians are working with government to try to arrive at policies and laws that provide a fair balance of protection of the public and recognition of the individual need to drive for the majority of people.
Acknowledgements: Contributors to this information were: Dr. R. Yee M.D., Arrhythmia Service, LHSC (UC), Dr. A. Krahn MD, Arrhythmia Service, LHSC (UC), and various staff members.