Syncope, Reflex (Vasovagal Syncope)

Description

• Derived from the Greek syncopa, “to cut short”
• Sudden, transient loss of consciousness characterized by unresponsiveness, falling, and spontaneous recovery
• Common cause of syncope in all age groups, especially in patients with no evidence of neurologic or cardiac disease
• Five main types of syncope: vasovagal or neurocardiogenic syncope, situational syncope, orthostatic hypotension, carotid sinus hypersensitivity, and glossopharyngeal/trigeminal neuralgia syncope (uncommon) (1)

Epidemiology

• Mortality: cardiac-related syncope 20–30% and 5% in idiopathic syncope
• Age: any age

Incidence

• Ranges from 7% in children aged <18 years and 15% in adults aged >70 years
• 36–62% of all syncopal episodes
• 30% recurrence rate

Prevalence
22% in the general population

Etiology and Pathophysiology

Cause: an abnormal response of the normal mechanisms that maintain BP in an upright posture; vasovagal syncope typically occurs when an individual is an upright position for a comparatively long duration (up to ≥10 minutes), compared with orthostatic hypotension which generally develops in a short period (such as a quick positional change).

• In normal individuals, upright posture results in venous pooling and transient decrease in BP.
• Neurally induced syncope may result from a cardioinhibitory response, a vasodepressor response, or a combination of the two.
• Increased cardiovagal tone leads to bradycardia or asystole, and decreased peripheral sympathetic activity leads to venodilation and hypotension (2).
• Vasovagal syncope usually has a precipitating event, often related to fright, pain, panic, exercise, noxious stimuli, or heat exposure (2).
• Carotid sinus syncope is precipitated by position change, turning head, or wearing a tight collar (possible neck tumors or surgical scarring).
• Situational syncope is related to micturition, defecation, postexercise, coughing, or swallowing.
• Glossopharyngeal syncope is related to throat or facial pain.

Genetics
Vasovagal syncope is associated with certain genetic markers, particularly involving serotonin and dopamine signaling (3).

Risk Factors

• Low-resting BP
• Age: older age
• Prolonged supine position with resulting deconditioning of autonomic control

General Prevention

Avoid precipitating events or situations. Optimize diabetes control, use of elastic stockings, and adequate hydration.

Commonly Associated Conditions

• Cardiopulmonary disorders: CHF, MI, arrhythmias, hypertrophic obstructive cardiomyopathy, HTN, pulmonary embolism (PE)
• Neurologic disorders: autonomic dysfunction, Shy-Drager syndrome, Parkinson disease, multiple system atrophy, transient ischemic attack, vertebrobasilar insufficiency, peripheral neuropathy
• Psychiatric disorders:
  • Generalized anxiety disorder
  • Panic disorder
  • Major depression
  • Alcohol dependence