The exact mechanism of syncope is still under study. In this condition, there appears to be a transitory fall in blood pressure due to the failure of peripheral resistance. This momentary fall in blood pressure causes a decreased flow of blood to the brain, leading to syncope, during which time there is a transient/brief form of unconsciousness, and the patient may fall to the ground, if he remains standing, i.e., does not sit, or lie immediately. Before his fall, he may feel some symptoms like nausea, giddiness, vertigo, disturbance of vision/hearing, blurring of vision or odd noises in the ears, body pallor, rapid respiration and sweating, etc.

If the attack is a prolonged one, in some of the cases, even twitching/jerky movements, or open convulsions may occur, thus creating some difficulty in diagnosing the condition clinically. Such attacks occur usually only in a standing/upright position. They do not occur when the patient is either lying down or sitting. The patient is not confused after the attack, although he still may be undergoing feelings of nausea.

This problem appears particularly in normal young adults, especially in females, with no obvious pathology which could account for these attacks. Such cases are usually seen in day-to-day practice, and can be embarrassing enough to cause anxiety.

The attacks are usually precipitated when a person keeps standing for a long time, e.g., as is sometimes seen in school students when they gather for their morning prayers (childhood syncope), or in older students standing for hours in various laboratories, and similarly in policemen and soldiers, when they happen to stand on duty at one place for a considerable length of time.

Also, the attacks are aggravated when a person suddenly stands up after lying down or sitting for a long period, or when the person gets up suddenly during his sleep at midnight/morning. Further, bad news or sight of blood, i.e., emotional shock, intense fear/pain, hot weather or a stuffy atmosphere, hunger, intake of excessive alcohol or loss of fluids, i.e., dehydration etc., may also initiate these attacks.

Recovery in vaso - vagal syncope occurs after the person lies down. There is no underlying cause. There is only a failure of peripheral resistance which causes the various conditions mentioned above.

Cardiac syncope

Cardiac syncope, i.e., syncope as a result of some underlying heart disease, occurs suddenly, without any warning symptoms. In such cases, there is a sudden fall in cardiac output/blood pressure, as a result of various diseases of the heart, like arrhythmias, such as when the heart rate is very high (paroxysmal atrial tachycardia-PAT, atrial fibrillation), or in a heart block (Stokes-Adams attack) when the heart rate becomes extremely slow, or in advanced cases of aortic stenosis (aortic valve disease), which result in a decreased flow of blood to the brain, etc. Hence detailed tests like electrocardiogram ECG (with a long rhythm strip), Holter monitoring (to detect arrhythmias), echocardiography (to detect aortic / other valvular diseases), etc., are required, besides an EEG, in some cases, for specific diagnosis and treatment.