Curriculum · Cardiovascular and Hypertension
Vasovagal syncope
What it is
Vasovagal syncope, or neurocardiogenic syncope, is loss of consciousness due to failure of autoregulation of blood pressure, which leads to decreased cerebral perfusion. The pathophysiology is reflex hypotension and bradycardia through the Bezold-Jarisch reflex. It is one of the reflex forms of syncope. Situational syncope is a type of neurogenic syncope triggered by particular settings, like micturition, defecating, or coughing. Carotid sinus hypersensitivity is an exaggerated vagal response to carotid stimulation, in which stimulation of the carotid sinus causes faintness, particularly in the elderly, by reflexively lowering the cardiac activity or by lowering the arterial pressure without slowing cardiac activity.
Causes and risk
Common causes and risk factors are pain, emotional stress, prolonged standing and dehydration; trauma is also given as a trigger. The episode follows an inciting event, and that event is stress or prolonged standing rather than exertion. That is what marks it off from cardiac syncope, which is sudden in onset with no prodrome, exertional or at rest, may have palpitations or chest pain, and has a high risk of sudden death.