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Patients, especially younger patients with normal ECGs and no structural heart disease, are usually strongly suspected of having an autonomic function disorder as the primary cause for syncope. “Autonomic” is another way of saying “related to the control of bodily functions, like digestion and breathing, without the patient’s awareness.”
The three most common types of autonomic function disorder are each neurally-mediated, or controlled by the nervous system:
- Vasovagal syncope (involving the interaction between the heart, blood vessels and the vagus nerve) – happens when the part of your nervous system that controls blood pressure and heart rate suddenly lowers them both for a short time, an exaggeration of a normal body reaction. As less blood flows to your brain, you may faint. This kind of syncope is also called neurocardiogenic syncope, reflex syncope and the common faint. It usually portends a benign prognosis and has a prevalence of up to 40% over the lifetimes of the general population. A subgroup of this type of syncope is situational syncope that can occur with specific activities as urination, coughing, choking, or laughing
- Carotid sinus syncope (caused by accidental pressure on the carotid sinus in the neck) – caused by the stimulation of the vagus nerve, leading to marked bradycardia and pauses
- Orthostatic hypotension is most often caused by volume depletion (loss of salt and fluid), but sometimes it can be a sign of generalized autonomic dysfunction. Usually, there is an identifiable cause, such as a systemic (affecting the body in general) disease like diabetes mellitus, a toxic substance like alcohol, or the use of a vasoactive medication used for treatment of hypertension.
One helpful method for differentiating among these types of syncope is tilt table test, which is performed routinely at Valley.