creation date: 2025-10-16 23:19
tags: Workups
Syncope
Background
Syncope refers to a transient loss of consciousness and postural tone followed by spontaneous recovery. This is often described as “fainting”, “blacking out”, or “passing out”.
Pathophysiology
Syncope is the result of a decrease in cerebral blood flow. This can be due to an interruption in blood flow or a drop in systemic blood pressure.
Cerebral blood flow is maintained by cardiac output, systemic vascular resistance, mean arterial pressure, and intravascular volume and any deficit in these systems can decreased blood flow.
With vasovagal syncope, initial sympathetic activity (caused by some stimuli or venous stasis) results in an overcompensating parasympathetic response that decreased HR and BP, causing decreased cerebral perfusion
Differential Diagnosis
Cardiovascular
- Cardiac arrhythmias
- Structural and obstructive disorders (eg. valvular abnormalities, MI, PE)
Cerebrovascular/neurological - Vertebrobasilar insufficiency
- Disrupted autoregulation
Disorders of blood flow and vascular tone - Vasovagal syncope (50% of all syncope cases)
- Prolonged standing, crowded environments, hot conditions, severe pain, extreme fatigue, stress causes vasodilation and bradycardia
- Orthostatic hypotension
- Situational causes (eg. coughing, defecation)
- Carotid sinus syncope
Disorders that mimic syncope - Seizures
- Metabolic conditions (eg. hypoglycemia)
- Psychogenic disorders (eg. panic attacks)
Initial Evaluation
History
Syncope may occur in even healthy individuals. Prodromal symptoms are common which includes:
- Blurred vision
- Diaphoresis
- Nausea
- Dizziness
- Weakness
There may be reports of a pale appearance and consciousness is regained within a few minutes. Episodes that are reported to last longer than a few minutes are more likely to be an acute neurologic process and further workup is warranted.
Contrasting to seizures, syncope episodes don’t involve loss of sphincter control, tonic-clonic activity, nor confusion upon regaining consciousness.
A distinction can be made between true syncope or pre-syncope/near syncope by gauging whether there was a loss of consciousness but the etiology and pathophysiology between both overlap.
History should also include:
- Preceding events
- Precipitating factors
- Post-event manifestations
Patient position at time of event (eg. standing vs. sitting) can suggest etiology, whereby standing is strongly suggestive of vasovagal syncope.
Risk stratification can be done for risk of serious outcomes using:
- EGSYS Score for Syncope (30 day risk of cardiac event)
- Canadian Syncope Risk Score (good if more labs available)
Physical Exam
Physical examination should focus on any abnormalities in vital signs which may hint at underlying disease (eg. orthostatic hypotension).
Cardiovascular and neurological exam should be included to elucidate underlying causes and rule out cerebrovascular events.
Investigations
A thorough history and physical may be sufficient as most cases are vasovagal and thus benign. Physical exam can generally rule out life-threatening causes.
In higher risk populations such as older adults, testing may include:
- Routine blood work (including CBC and electrolytes)
- Electrocardiogram / Holter
- Blood glucose
If cardiac or cerebrovascular etiology is suspected, testing may include cardiac enzymes and head CT.
Suspicion of seizures can be evaluated with EEG.