Link To And Excerpts From StatPearls’ “Syncope”

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Today, I review, link to, and excerpt from StatPearlsSyncope. Shamai A. Grossman; Madhu Badireddy. Last Update: June 12, 2023.

All that follows is from the above resource.


Syncope is caused by decreased cerebral blood flow leading to transient loss of consciousness and postural tone, associated with spontaneous recovery. Symptoms like dizziness, lightheadedness, diaphoresis, nausea, and visual disturbances may precede it or occur suddenly with none of the above symptoms. Syncope is a symptom described as fainting, blacking out, falling out, or “having a spell,” and represents 1 to 3.5% of all emergency department visits and 6% of all hospital admissions in the United States. This large number of emergency department visits and admissions reflect the varied etiologies of syncope from benign to life-threatening and the high degree of diagnostic uncertainty associated with this symptom.


Syncope is a symptom of an underlying disease process rather than a disease itself. Although syncope mimics a death-like experience eliciting extreme consternation among both patients and their families, most syncopal events have a benign cause.  Benign causes of syncope reflect vasovagal (also known as neurocardiogenic), volume depletion, or medication-related etiologies. More ominous causes are related to dysrhythmia and valvular abnormalities such as ventricular tachycardia, atrioventricular (AV) block, or critical aortic stenosis. A history of left ventricular dysfunction (with concomitant degeneration of the conduction system leading toward a propensity for dysrhythmias) has been found to be the most ominous predictor of an adverse etiology of a syncopal event.

Causes of Syncope

1. Cardiovascular disorders

  • Cardiac arrhythmias (both tachy and bradyarrhythmias)
  • Structural and obstructive disorders (valvular abnormalities, HOCM, MI, PE)

2. Cerebrovascular causes (vertebrobasilar insufficiency)

3. Disorders of blood flow and vascular tone

  • Vasovagal (neurocardiogenic)
  • Orthostatic hypotension (medications, autonomic failure, peripheral neuropathy, decreased blood flow)
  • Situational (cough, micturition, defecation, postprandial, deglutition)
  • Carotid sinus syncope

4. Others that mimic syncope

  • Seizures
  • Metabolic (hypoglycemia, hypoxia, symptomatic anemia)
  • Psychogenic (panic attacks)

Vasovagal Syncope (Neurocardiogenic syncope, Common faint)

This accounts for almost 50% of all cases of syncope. When faced with certain situations like prolonged standing, crowded places, hot environment, severe pain, extreme fatigue and stress leads to vasodilatation (sympathetic withdrawal) and bradycardia (parasympathetic activity). This condition is also called common faint as it is the common cause of syncope and can occur even in normal people. Syncope events are preceded by prodromal symptoms like blurred vision, diaphoresis, nausea, dizziness, weakness, and then leads to bradycardia, decreased blood pressure, and then lose consciousness. Patients appear pale to the onlookers. Patients normally regain consciousness in few minutes and may experience generalized weakness. They do not lose sphincter control, rarely have any tonic-clonic activity or confusion after regaining consciousness as in patients with seizures.


Syncope accounts for around 1 to 3.5% of visits to emergency department visits in the US. Syncope is more common in older patients due to multiple comorbidities and multiple medications. Cardiac etiology is more common in older patients and noncardiac etiology (vasovagal) common in young adults. There is no significant difference in incidence between men and women.


The brain needs a constant supply of glucose (through adequate cerebral blood flow) to function and any interruption to this even for few seconds can lead to loss of consciousness or syncope. Cerebral blood flow is maintained by a complex mechanism involving cardiac output, systemic vascular resistance, mean arterial pressure, and intravascular volume. Any defect in one or more of these systems leads to decreased cerebral blood flow. Approximately three-fourths of blood is in the venous bed and any interference in venous return can lead to decreased cardiac output.

Any episode lasting more than a few minutes is not syncope and is more likely to be related to a seizure or other acute neurologic process. Seizures are the most common disease misdiagnosed as syncope. When symptoms overlap too closely, the only way to differentiate seizure from syncope may be with an EEG.

Treatment / Management

Treatment of underlying cause is the focus of treatment in syncope.

Disposition is often the most difficult task in caring for emergency department patients with syncope. Admission rates vary in patients presenting with syncope. In the United States, about 80% of patients presenting to the emergency department following a syncopal event will be admitted.

Follow-up: Patients with unknown etiology and without underlying heart disease have a good outcome. Patients with syncope and underlying heart disease needs regular follow-up with a primary care physician and cardiologist.

Differential Diagnosis

Important differential diagnosis for syncope include

1. Seizure disorder: Seizures associated with aura, tonic-clonic activity, prolonged duration of unconsciousness, urinary and/or bowel incontinence, tongue biting and confusion after regaining consciousness. These differentiate syncope from seizures.

2. Hypoglycemia.

3. Panic attacks: Feeling impending doom, palpitations, air hunger and tingling of perioral region and tips of fingers.


Prognosis depends upon the underlying cause, so identification of the cause is very important. The annual mortality rate can range from 0 to 12% in patients with noncardiac cause and 18 to 33% in patients with a cardiac cause. 


Patients can sustain injuries from fall due to syncope. These injuries can be worse if they were driving during the event.

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