A sudden, transient, self-limited loss of consciousness with an inability to maintain postural tone that is followed by spontaneous recovery. This definition excludes seizures, coma, shock, or other states of altered consciousness.

Obtaining a thorough Past History is vital to establishing a likely cause. In at least 50% of cases an underlying cause is not found.

Common categories:

• Neurally‐mediated (reflex) syncope - probably around 70%
  • emotional and orthostatic stress
  • associated with other function eg micturition, sneeze, cough, defaecate
  • carotid sinus syncope - when carotid sinus mechanically manipulated
• Orthostatic hypotension
  • ANS fails to respond to posture changes eg Parkinsons, dementia, diabetes, uremia, spinal injury
  • drug related eg alcohol, vasodilators, antidepressants
  • volume depletion - eg blood loss, D&V, diuretics
• Cardiac arrhythmias - probably around 10%
  • bradys and tachys, heart block, pacemaker related
• Structural heart disease
• 'Steal' syndromes
  • rare - eg. subclavian steal syndrome

• various decision rules have been tested and focus on identifying high risk patients. Usually result in over admission:
  • San Francisco Syncope Rule (also known as CHESS criteria)
  • ROSE (Risk stratification of Syncope in ED) -
• when pathology seems causative, eg cardiac cause, prognosis is worse
• vaso-vagal - good prognosis
• background of cardiac disease has worse prognosis regardless of causation of presenting syncopal episode

• exertional onset, chest pain, dyspnea, palpitations
• low back pain
• severe headache, focal neurologic deficits, diplopia, ataxia, or dysarthria

ROSE rule - BRACES admit if any of the following:

• BNP ≥300pg/ml, Bradycardia ≤50
• Rectal blood
• Anaemia ≤90
• Chest pain
• ECG with Q wave except III
• Saturation ≤94% room air

San Francisco Syncope Rule - CHESS criteria admit if any of the following:

• Congestive Heart Failure History
• Hematocrit <30%
• ECG Abnormal?
• Shortness of Breath History?
• sBP <90 mmHg at Triage

• a selective neuropathy of sympathetic and parasympathetic nervous system of unknown aetiology
• insidious, arising mainly in middle to late age
• men 5x women
• no cognitive or central dysfunction
• impotence, post-prandial problems and nocturia are common
• wide range of 'vague' autonomic symptoms
• prodrome of sweating, tachycardia and pallor seen in vasovagal syncope does not occur

NCBI diagnosis and treatment of syncope
https://emedicine.medscape.com/article/811669-overview#a3
J Am Cardiol ROSE study
Cardiology in Review: Orthostatic hypotension and vasovagal syncope 2008