Syncope
Syncope is a transient loss of consciousness from global cerebral hypoperfusion with spontaneous complete recovery. The central task is separating benign reflex and orthostatic causes from dangerous cardiac syncope, using history, examination, and ECG, since cardiac syncope carries a risk of sudden death; treatment is directed by mechanism, from reassurance and hydration for reflex syncope to a pacemaker, ICD, or structural intervention for cardiac syncope.
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What this article covers
- Overview
Definition: syncope is a transient loss of consciousness due to global cerebral hypoperfusion, characterized by rapid onset, short duration, and spontaneous complete recovery.
- Epidemiology
Very common, a frequent emergency and clinic presentation.
- Risk factors
For reflex syncope: young age, prolonged standing, heat, pain, and emotional triggers.
- Pathophysiology
Global cerebral hypoperfusion: a transient fall in cerebral blood flow causes loss of consciousness.
- Clinical features
Reflex syncope: a prodrome (nausea, warmth, diaphoresis, visual dimming), often with a clear trigger and postural context.
- Differential diagnosis
Reflex (vasovagal, situational, carotid sinus) syncope: a clear trigger and autonomic prodrome with a normal ECG and heart, the most common and benign cause.
- Diagnosis
Establish the mechanism with history, examination, orthostatic vitals, and ECG, then risk-stratify: the diagnostic basis is a detailed history of the event and triggers, cardiovascular and neurologic…
- Management
First-line, treat by mechanism and address reversible causes: for reflex syncope, reassurance, education on triggers and counter-pressure maneuvers, and adequate hydration and salt; stop or reduce offending vasoactive drugs.
- Complications
Injury from falls (fractures, head injury).
- Prognosis
Excellent for reflex and orthostatic syncope.
- Prevention
Trigger avoidance, hydration (2 to 3 liters/day), and counter-pressure maneuvers for reflex syncope.
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Related articles
- Orthostatic hypotension
Orthostatic hypotension is a sustained fall in blood pressure on standing (at least 20 mmHg systolic or 10 mmHg diastolic), causing lightheadedness, presyncope, and falls. Causes include volume depletion, drugs, and autonomic failure; management is removing offenders, nonpharmacologic measures, and, when needed, fludrocortisone or midodrine.
- Postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome is an excessive heart-rate rise on standing (at least 30 beats per minute) with orthostatic symptoms but without orthostatic hypotension. It predominantly affects young women, is diagnosed after excluding other causes, and is managed with volume expansion, exercise reconditioning, and rate-modulating drugs.
- Sudden cardiac arrest
Sudden cardiac arrest is the abrupt cessation of cardiac function with loss of pulse and consciousness, most often from a ventricular tachyarrhythmia on a background of coronary disease. Survival depends on immediate CPR and defibrillation of shockable rhythms, followed by treatment of the cause and secondary prevention with an ICD.
- Ventricular tachycardia
Ventricular tachycardia is three or more consecutive ventricular beats at over 100 per minute, a wide-complex tachycardia that is life-threatening when sustained. Any regular wide-complex tachycardia is ventricular tachycardia until proven otherwise: unstable patients are cardioverted or defibrillated, and long-term risk is managed with an implantable defibrillator.
- Aortic stenosis
Aortic stenosis is obstruction to left ventricular outflow from a narrowed aortic valve, most often calcific degeneration in older adults or a bicentric bicuspid valve earlier in life. Symptoms of angina, syncope, or heart failure mark a poor prognosis, and severe symptomatic disease is treated with valve replacement (surgical or transcatheter).