Also Known As: Vasovagal syncope, Vasovagal episode, Neurocardiogenic syncope
A vasovagal episode or vasovagal response or vasovagal attack (also called neurocardiogenic syncope) is a malaise mediated by the vagus nerve. When it leads to syncope or "fainting", it is called a vasovagal syncope, which is the most common type of fainting.
There are a number of different syncope syndromes which all fall under the umbrella of vasovagal syncope. The common element among these conditions is the central mechanism leading to loss of consciousness. The differences among them are in the factors that trigger this mechanism.
Among people with vasovagal episodes, the episodes are typically recurrent, usually happening when the person is exposed to a specific trigger. Prior to losing consciousness, the individual frequently experiences a prodrome of symptoms such as lightheadedness, nausea, the feeling of being extremely hot (accompanied by sweating), ringing in the ears (tinnitus), uncomfortable feeling in the heart, fuzzy thoughts, a slight inability to speak/form words (sometimes combined with mild stuttering), weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision, and sometimes a feeling of nervousness can occur as well. These last for at least a few seconds before consciousness is lost (if it is lost), which typically happens when the person is sitting up or standing. When sufferers pass out, they fall down (unless this is impeded); and when in this position, effective blood flow to the brain is immediately restored, allowing the person to regain consciousness. Short of fainting a person may experience an almost indescribable weak and tired feeling resulting from a lack of oxygen to the brain due to a sudden drop in blood pressure. Taber's Cyclopedic Medical Dictionary describes this as the "feeling of impending death" caused by expansion of the aorta, drawing blood from the head and upper body.
The autonomic nervous system's physiologic state (see below) leading to loss of consciousness may persist for several minutes, so:
- If sufferers try to sit or stand when they wake up, they may pass out again
- The person may be nauseated, pale, and sweaty for several minutes or hours
- Vasovagal syncope occurs in response to a trigger(stress, postural change, extreme emotion) with a corresponding malfunction in the parts of the nervous system that regulate heart rate and blood pressure. When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain causes fainting.