Vasovagal syncope

This is caused by autonomic overactivity, usually provoked by emotional or painful stimuli, less commonly by coughing or micturition. It is also called as neurocardiogenic syncope.

The mechanism is that directly or indirectly, the nucleus tractus solitarius is activated by the triggering stimuli and this leads to increased parasympathetic tone and decreased sympathetic tone.
The vagal parasympathetic tone leads to negative chronotropic and negative inotropic effects. This causes a slowing in the heart rate and decreased contractility that leads to a drop in the cardiac output.
The decreased sympathetic tone on the other hand leads to vasodilation which leads to a decrease in the total peripheral resistance.
Both cause a decrease of blood pressure significant enough to lead to loss of consciousness.

'Malignant' vasovagal syndrome is a rare condition where syncopal attacks so frequent that they are significantly disabling .

Recovery is rapid if the patient lies down.

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