Syncope

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Definition

Syncope is a transient loss of consciousness (TLOC) due to global cerebral hypoperfusion characterized by rapid onset, short duration and spontaneous complete recovery. This excludes other causes of TLOC such as neurological, psychological and metabolic causes.

Classification

Syncope can be classified into:

• Reflex syncope
  • Vasovagal
    • mediated by orthostatic or emotional stress
  • Situational
    • Cough
    • Sneeze
    • Gastro-intestinal (swallow, defaecation, visceral pain)
    • Micturation
    • Post-exercise
    • Post-prandial
    • Others (e.g. laugh, brass instrument playing, weightlifting)
  • Carotid sinus syncope
  • Atypical forms
    • without apparent triggers and/or atypical presentation
• Syncope due to orthostatic hypotension
  • Primary autonomic failure
    • Pure autonomic failure
    • Multiple system atrophy
    • Parkinson's disease with autonomic failure
    • Lewy body dementia
  • Secondary autonomic failure
    • Diabetes
    • Amyloidosis
    • Uraemia
    • Spinal cord injuries
  • Drug induced orthostatic hypotension
    • Alcohol, vasodilators, diuretics, phenotiazines, antidepressants
  • Volume depletion
    • Haemorrhage, diarrhoea, vomiting etc.
• Cardiac syncope
  • Arrhythmias
    • Bradycardia: sinus node dysfunction, atrio-ventricular conduction system disease, implanted device malfunction.
    • Tachycardia: supraventricular, ventricular (idiopathic, secondary to structural heart disease or to channelopathies)
    • Drug-induced arrhythmias
  • Structural heart disease
    • Cardiac: cardiac valvular disease (or prosthetic valve dysfunction), acute myocardial infarction/ischemia, hypertrophic cardiomyopathy, cardiac masses, pericardial disease/tamponade, congenital anomalies of coronary arteries
    • Other: pulmonary embolus, acute aortic dissection, pulmonary hypertension

Pathophysiology

(Figure pathophysiology syncope)

Epidemiology

Syncope is common in the general population. The life-time cumulative incidence of ≥1 syncopal episodes in teenagers in the general population is high, with about 40 % by the age of 21 years. Reflex syncope is by far the most common cause. The majority have experienced reflex-mediated syncope episodes as teenagers and adolescents. The frequency of cardiac syncope increases with age. Approximately 10-30% of the syncope episodes in patients above 60 years visiting a hospital for their syncope episodes are of cardiac origin.

Reflex syncope

Treatment

The prognosis of reflex syncope is excellent.

Orthostatic hypotension

Cardiac syncope