Posted by e-Medical PPT
Syncope is the medical term for fainting, a sudden, usually temporary, loss of consciousness generally caused by insufficient oxygen in the brain either through cerebral hypoxia or through hypotension, but possibly for other reasons. A pre- or near-syncope is diagnosed if the individual can remember events during the loss of consciousness.
Vasovagal (situational) syncope—one of the most common types—may occur in scary, embarrassing or uneasy situations, or during blood drawing, coughing, urination or defecation. Other types include postural syncope (caused by a changing in body posture), cardiac syncope (due to heart-related conditions), and neurological syncope (due to neurological conditions). There are many other causes of syncope, including low blood-sugar levels and lung disease such as emphysema and a pulmonary embolus. The cause of the fainting can be determined by a doctor using a complete history, physical, and various diagnostic tests.
The vasovagal type can be considered in two forms:
    * Isolated episodes of loss of consciousness, unheralded by any warning symptoms for more than a few moments. These tend to occur in the adolescent age group, and may be associated with fasting, exercise, abdominal straining, or circumstances promoting vaso-dilation (e.g., heat, alcohol). The subject is invariably upright. The tilt-table test, if performed, is generally negative.
    * Recurrent syncope with complex associated symptoms. This is so-called Neurally Mediated Syncope (NMS). It is associated with any of the following: preceding or succeeding sleepiness, preceding visual disturbance ("spots before the eyes"), sweating, light-headedness. The subject is usually but not always upright. The tilt-table test, if performed, is generally positive.
Cardiac arrhythmias is the most common cause of cardiac syncope. Two major groups of arrhythmias are bradycardia and tachycardia. Bradycardia can be caused by heart blocks. Tachycardias include SVT (supraventricular tachycardia) and VT (ventricular tachycardia). SVT does not cause syncope except in Wolff-Parkinson-White syndrome. Ventricular tachycardia originate in the ventricles. VT causes syncope and can result in sudden death. Ventricular tachycardia, which describes a heart rate of over 100 beats per minute with at least three irregular heartbeats as a sequence of consecutive premature beats, can degenerate into ventricular fibrillation, which requires DC cardioversion.
Aortic stenosis and mitral stenosis are the most common examples.Aortic stenosis presents with repeated episodes of syncope. Pulmonary embolism can cause obstructed blood vessels. High blood pressure in the arteries supplying the lungs (pulmonary artery hypertension) can occur during pulmonary embolism. Rarely, cardiac tumors such as atrial myxomas can also lead to syncope.

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