Updated on 05/01/2024
Syncope is the sudden and temporary loss of consciousness due to impaired cerebral blood flow. Recovery is rapid and complete. In other words, a person who faints almost always recovers without treatment. However, traumatic injuries can occur during fainting, and recurrent episodes can be frightening. Therefore, identifying the cause of fainting is important in order to prevent and treat it. There are other causes of fainting, such as low blood sugar, hyperventilation, falling, or having an epileptic seizure. These are not syncope, but their detection is important for treatment.
Syncope is surprisingly common in the community. Its prevalence is 22%. About one-third of people will experience one episode of syncope at some point in their lives. Some syncope have significant underlying problems, while others do not.
1. Vasovagal syncope is the most common syncope. Typically it depends on the situation (e.g. on the toilet at night, in the heat, in a very crowded environment). There are certain triggers (e.g. standing tall, emotional trauma, pain, coughing, swallowing, peeing, seeing blood). Sometimes vasovagal syncope can happen without any obvious cause whatsoever.
Heart rate slows down considerably during fainting, the veins expand and the blood pools, especially in the legs and intestines, as a result of which blood return to the heart decreases and blood pressure drops. This causes a decrease in blood flow to the brain.
Vasovagal syncope is usually benign. In most cases, there are warning signs that make us realize we are going to pass out. These symptoms are drowsiness, feeling hot or cold, blurred, double, pale or tunnel-like vision, hearing impairment, and sweating. However, fainting without provocation or warning signs, or when an elderly person faints for the first time, suggests a more serious heart disease.
2. Heart rhythm problems, as in problems with heart rate or rhythm cause fainting. We call these disorders arrhythmias. Various arrhythmias such as sinus bradycardia, heart block, ventricular tachycardia, supraventricular tachycardia can cause syncope.
3. Orthostatic hypotension is when a person stands up and experiences low blood pressure. The causes of orthostatic hypotension may be blood and fluid loss, some drugs, some nervous system diseases and alcohol.
4. Other causes are syncope due to breath-holding, certain poisonings, low blood sugar, postural tachycardia syndrome, heart attack, heart tumour or clot in the pulmonary vessels.
Fainting has 3 phases;
2. Loss of consciousness
Prodrome lasts about 1-5 minutes in vasovagal syncope and dizziness, nausea, sweating, and blackout may be observed. Loss of consciousness lasts usually less than 1 minute and is accompanied by facial pallor, sweating, and cold skin. The eyes are open or turned up, and there may sometimes be stiffness and thrashing of the arms and legs. Urinary incontinence and self-mutilation are rare, and biting the side of the tongue is extremely rare. Recovery is rapid and confusion resolves within seconds after fainting.
In regards to differential diagnosis, other diseases that cause fainting should be excluded first. To this end, the history of the disease, physical examination and heart examinations prove to be useful. Heart examinations include ECG, Holter monitoring heart rhythm for 24-48 hours, echocardiography, tilt-table test. In addition, some neurological diseases such as epilepsy, basilar migraine and narcolepsy are also included in the differential diagnosis.
Treatment for vasovagal syncope is usually to avoid triggers and reduce the potential risk. For example, if you faint while giving blood, you should have blood drawn while lying down. Or if you feel that you will pass out during an activity, you should immediately lie down and raise your legs in the air. Or, counter-pressure manoeuvres (such as stretching the arms, crossing the legs and squeezing) can prevent vasovagal syncope or give you time to reach out.
People with heart rhythm disorders are treated with the appropriate methods. These treatments may be arrhythmia drugs, pacemakers or implanted defibrillators.
If orthostatic hypotension is detected, elastic compression stockings can be worn, the legs can be compressed before standing up, or one may rise gradually.
In many cases, syncope is not dangerous. However, it can be dangerous if you fall and injure yourself when you faint. It can also be dangerous to faint while driving. If you occur to faint, you should definitely see a doctor. That Is because some syncopes may have serious and treatable causes. It would be helpful to give your doctor some information in the history. What were you doing before you fainted, how did you feel before you fainted, how long were you unconscious, did you return to normal when you sobered up, have you ever fainted before, and what medications do you use. If there is someone who sees you fainting, it will be helpful to go to the examination together with them.
Benditt D. Syncope. Up To Date Mar 21, 2019
Smith P.E.M. Fainting painting. Practical Neurology, 2005, 5, 366–369.