Syncope

Signs and Symptoms

Syncope, also known as fainting, or a sudden and brief loss of consciousness, occurs when the brain does not get enough blood flow and oxygen.

There are many causes of syncope. A common type of syncope -- vasovagal syncope or neurocardiogenic syncope -- is caused by a malfunction of the nerves that control the action of the heart and blood vessels, called the autonomic nervous system. This type of syncope may be triggered by fear, severe pain, emotional distress or standing for a long time. Dehydration and low salt intake may also contribute to the condition.

Syncope may also be caused by very fast heart rhythms or arrhythmias called tachycardias, as in supraventricular tachycardia (SVT) (link to SVT) or ventricular tachycardia (VT) (link to VT). In some cases, syncope is caused by very slow heart rhythms, called bradycardias, as in sinus node dysfunction (SND) (link) or heart block (link).

The hallmark symptom of syncope is fainting, or near fainting. The condition may also cause the following symptoms:

• Palpitations, which can be skipping, fluttering or pounding in the chest
• Fatigue
• Chest pressure or pain
• Shortness of breath
• Vision changes
• Nausea
• Lightheadedness or dizziness

Diagnosis

Syncope or near syncope may occur spontaneously with unpredictable timing. Therefore, in many cases, the condition requires specialized tests to acquire an accurate diagnosis. If your doctor suspects that your child has syncope, one or more of the following diagnostic tests to determine the source of your child's symptoms will be ordered:

Electrocardiogram -- An electrocardiogram (ECG or EKG) records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs, and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.

Holter Monitor -- A Holter monitor is a small, portable machine that your child wears for 24 hours. It is about the size of a portable tape player and provides a continuous 24-hour recording of your child's heartbeat onto a tape. You will be asked to keep a diary of your child's activities and symptoms. This monitor may detect arrhythmias that might not show up on a resting electrocardiogram, which only records a heartbeat for a few seconds at rest.

Event Monitor -- This is a small monitor about the size of a pager that your child can have for up to a month. Since the syncope may occur at unpredictable times, this will help to record the abnormal rhythm when your child is experiencing symptoms. He or she can just push a button on the pager and record the heartbeat. The recording can than be transmitted by phone to the doctor.

Stress Test -- An exercise stress or treadmill test, records the electrical activity of your child's heart during exercise, which differs from the heart's electrical activity at rest.

Electrophysiology Study -- In an electrophysiology (EP) study, doctors insert special electrode catheters -- long, flexible wires -- into veins and guide them into the heart. These catheters sense electrical impulses and also may be used to stimulate different areas of the heart. Doctors can then locate the sites that are causing arrhythmias. The EP study allows doctors to examine an arrhythmia under controlled conditions and acquire more accurate, detailed information than with any other diagnostic test.

Tilt Table Test -- If your child has a history of syncope, your doctor may perform a tilt table test to determine how their body responds to changes in position. During the test, your child will lie on a table that can be tilted upright to 70 degrees with constant monitoring of blood pressure and heart rate.

The tilt test is designed to provoke syncope under controlled conditions. It is especially helpful in the diagnosis of children with vasovagal syncope. While the patient is tilted upright blood will collect or pool in the lower part of the body, which causes less blood to return to the heart and the blood pressure to drop. Normally, the body's nervous system responds by increasing the heart rate and constricting the blood vessels to maintain blood pressure. However, in children with vasovagal syncope, the nervous system does not respond as it should, and the heart rate slows and the blood pressure drops, which may cause a loss of consciousness. If this occurs, the patient is placed flat immediately and normal blood flow is restored.

Treatment

Because there are various reasons for syncope, the treatment for your child's syncope depends on the cause. Syncope may be caused by very fast heart rhythms -- tachycardias -- such as in supraventricular tachycardia (SVT) or ventricular tachycardia (VT). In other cases, syncope may be caused by very slow heart rhythms -- bradycardias -- such as in sinus node dysfunction or heart block.

If your child's syncope is due to a blood pressure problem, medications, extra fluid intake and salt may be recommended.