Vasovagal
| Vasovagal syncope | |
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| Synonyms | Vasovagal episode, vasovagal response, neurocardiogenic syncope |
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| Vagus nerve | |
| Specialty | Neurology, cardiovascular |
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Vasovagal syncope is a sudden brief loss of consciousness (syncope) due to activation of the vagus nerve. This activation may occur due to triggers, such as the sight of blood or emotional distress. The underlying mechanism involves the sudden drop in blood pressure. It is the most common type of fainting.
There are different syncope syndromes that fall under the umbrella of vasovagal syncope. The common element among these conditions is the central mechanism which may lead to the loss of consciousness. The differences among them are in the factors that trigger this mechanism.
Episodes of vasovagal syncope are typically recurrent and usually occur when the predisposed person is exposed to a specific trigger. Before losing consciousness, the individual frequently experiences early signs or symptoms such as lightheadedness, nausea, the feeling of being extremely hot or cold (accompanied by sweating), ringing in the ears, an uncomfortable feeling in the heart, fuzzy thoughts, confusion, a slight inability to speak or form words (sometimes combined with mild stuttering), weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision, black cloud-like spots in vision, and a feeling of nervousness can occur as well. The symptoms may become more intense over several seconds to several minutes before the loss of consciousness (if it is lost). Onset usually occurs when a person is sitting up or standing.
When people lose consciousness, they fall down (unless prevented from doing so) and, when in this position, effective blood flow to the brain is immediately restored, allowing the person to regain consciousness. If the person does not fall into a fully flat, supine position, and the head remains elevated above the trunk, a state similar to a seizure may result from the blood's inability to return quickly to the brain, and the neurons in the body will fire off and generally cause muscles to twitch very slightly but mostly remain very tense. Fainting occurs with a loss of oxygen to the brain.
The autonomic nervous system's physiological state (see below) leading to loss of consciousness may persist for several minutes, so
Vasovagal syncope occurs in response to a trigger due to dysfunction of the heart rate and blood pressure regulating mechanism. When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain causes fainting and confusion.
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