What is syncope?

What is Syncope?

Syncope is a symptom that presents with an abrupt, transient, complete loss of consciousness, associated with inability to maintain postural tone, with rapid and spontaneous recovery, where the presumed mechanism is cerebral hypoperfusion. 1

Definition and Mechanism

Syncope results from inadequate cerebral blood flow, leading to temporary interruption of brain function. Key characteristics include:

• Rapid onset and short duration (typically less than a minute)
• Spontaneous complete recovery without intervention
• Inability to maintain postural tone (falling)
• Global cerebral hypoperfusion as the underlying mechanism 2

Syncope must be distinguished from other conditions causing loss of consciousness such as seizures, hypoglycemia, metabolic conditions, drug intoxication, or head trauma 1.

Classification of Syncope

Syncope can be classified into three main categories:

1. Reflex (Neurally-Mediated) Syncope:

   • Vasovagal syncope (common fainting)
   • Situational syncope (triggered by coughing, urination, etc.)
   • Carotid sinus hypersensitivity

2. Orthostatic Hypotension:

   • Initial (immediate) orthostatic hypotension
   • Classic orthostatic hypotension
   • Delayed orthostatic hypotension
   • Neurogenic orthostatic hypotension

3. Cardiac Syncope:

   • Arrhythmias
   • Structural heart disease
   • Other cardiovascular conditions (pulmonary embolism, aortic dissection) 2

Epidemiology

• Affects approximately one-third of the population at least once during their lifetime
• Follows a trimodal distribution with peaks around ages 20,60, and 80 years
• More common in females (22%) than males (15%)
• Accounts for up to 3% of emergency department visits and 6% of hospital admissions 2
• Prevalence rates as high as 41%, with recurrent syncope occurring in 13.5% of cases 1

Clinical Presentation

Patients may experience:

• Prodromal symptoms (presyncope): Extreme lightheadedness, visual disturbances ("tunnel vision" or "graying out"), nausea, sweating, pallor, and palpitations 1
• During episode: Complete loss of consciousness, falling, and inability to maintain posture
• Post-syncope: Rapid recovery of consciousness, though many patients feel tired afterward; children especially may fall asleep 1

Prognosis and Risk

The prognosis varies significantly based on the underlying cause:

• Reflex and orthostatic syncope: Generally benign with good prognosis
• Cardiac syncope: Associated with increased morbidity and mortality, including risk of sudden cardiac death 2, 3

Common Pitfalls and Caveats

1. Misdiagnosis: Syncope can be confused with seizures, especially when myoclonic jerks are present (occurs in up to 90% of adolescents with syncope) 2

2. Overlooking cardiac causes: Even a single syncopal episode in a patient with structural heart disease requires thorough evaluation due to higher mortality risk 2

3. Medication-induced syncope: Always review medication lists, especially in older adults taking antihypertensives, vasodilators, diuretics, antidepressants, or antipsychotics 2

4. Injury risk: Syncope can lead to injuries such as fractures and intracranial hemorrhage in approximately 30% of cases 2

5. Post-vaccination syncope: Particularly common in adolescents and young adults; monitoring for 15-20 minutes after vaccination is recommended to prevent injury 2

Understanding the specific cause of syncope is crucial for appropriate management and risk stratification, as some forms (particularly cardiac syncope) can be warning signs of potentially life-threatening conditions.