Syncope, or fainting, is a sudden and brief loss of consciousness from which recovery is spontaneous. Syncope is common and disabling, but its causes are difficult to diagnose. An important issue is distinguishing syncope from several other symptoms. Dizziness, presyncope, and vertigo do not result in a loss of consciousness. Vertigo is associated with a sense of motion.
Distinguishing syncope from seizure can sometimes be difficult. However, a loss of consciousness that is precipitated by pain, exercise, urination, defecation, or stressful events is usually associated with syncope and not seizure. Also, disorientation after the event, slowness in returning to consciousness, and unconsciousness lasting more than five minutes suggest a seizure.
Syncope often leads to hospital admission, multiple consultations, and the performance of many diagnostic tests.
What causes syncope?
The most common cause of syncope is a vasovagal attack - also termed neurocardiogenic syncope. Examples of vasovagal syncope include emotional fainting and situational syncope (caused by cough, urination, or defecation). Vasovagal syncope may also be associated with symptoms such as sweating, nausea, and a clammy sensation.
The mechanism that causes vasovagal syncope is not well understood, syncope may be caused by blood pressure falling excessively when a patient stands (orthostatic hypotension). This can be caused by dehydration and by certain medications, but is also common in older patients. Episodes of syncope in athletes who don't have heart disease are usually vasovagal.
When should I worry about syncope?
The presence of heart disease - coronary artery disease, congestive heart failure, valvular heart disease or congenital heart disease - has emerged as the most important factor for predicting the risk of an adverse event. Although syncope may represent a simple fainting spell, syncopal episodes should be reported to your physician for evaluation and possible treatment.
Patients with heart disease and/or abnormal electrocardiogram have an increased risk of adverse events. Most arrhythmias are found in these patients. Since syncope caused by arrhythmias can be more dangerous, a more extensive evaluation may be required.
How is syncope diagnosed?
Syncope is diagnosed through:
- A careful history and physical examination
- An electrocardiogram
- 24-hour Holter monitoring
Additional diagnostic tests include:
- Echocardiogram
- Tilt-table testing
- Event recorder
- Electrophysiological testing
- Carotid artery ultrasound
