What is near-syncope (pre-syncopal state)?

Definition of Near-Syncope

Near-syncope (presyncope) is defined as a sensation of imminent fainting characterized by symptoms such as lightheadedness, dizziness, blurred vision, nausea, sweating, and pallor, without complete loss of consciousness, representing the prodrome of syncope caused by transient cerebral hypoperfusion. 1

Clinical Characteristics of Near-Syncope

Near-syncope presents with a constellation of symptoms that occur when cerebral perfusion is compromised but not enough to cause complete loss of consciousness:

• Typical symptoms include:

  • Lightheadedness/faintness
  • Dizziness
  • Visual disturbances (black spots, blurred vision, "tunnel vision")
  • Nausea
  • Feeling warm/hot or cold
  • Abdominal pain 2

• Typical signs include:

  • Pallor/paleness
  • Sweating
  • Vomiting
  • Shivering
  • Sighing
  • Diminished postural tone
  • Confusion 2

Pathophysiology

Near-syncope occurs due to the same mechanisms as syncope but without progression to complete loss of consciousness:

1. Transient cerebral hypoperfusion is the underlying mechanism 2
2. Common causes include:
   • Vasovagal origin - decreased venous return to the heart, leading to reduced cardiac output and cerebral perfusion 1
   • Orthostatic origin - drop in blood pressure when standing (≥20 mmHg systolic or ≥10 mmHg diastolic) 1
   • Cardiac causes - arrhythmias or structural heart disease 2

Clinical Significance

Near-syncope should not be dismissed as less significant than syncope:

• Multiple prospective studies have shown that both short-term serious outcomes and deaths in patients with syncope and presyncope are extremely similar 2
• Management and risk stratification of patients with syncope and presyncope should mirror one another, a concept endorsed by various medical societies 2
• The SPEED study found that patients with near-syncope do not differ significantly from patients with syncope regarding etiologies, laboratory values, vital parameters, or accompanying medical conditions 3

Diagnostic Considerations

When evaluating near-syncope, consider:

1. Is it truly near-syncope? Differentiate from other conditions like vertigo, seizures, or anxiety
2. What is the underlying cause? Vasovagal, orthostatic, cardiac, neurological, or metabolic
3. Is there high risk for adverse outcomes? Age, heart rate, and renal dysfunction are independent predictors of undesired events 3

Clinical Approach

The European Heart Journal guidelines emphasize that the term "presyncope" or "near-syncope" describes a state resembling the prodrome of syncope but not followed by loss of consciousness. There remain some doubts about whether the mechanisms involved are exactly the same as in syncope, but the clinical approach should be similar 2.

Key Points to Remember

• Near-syncope should be taken as seriously as syncope in terms of evaluation and management
• The underlying causes of near-syncope are the same as those for syncope
• Cardiac causes of near-syncope carry a higher risk of mortality than non-cardiac causes 4
• Patients with near-syncope are typically younger and more commonly male than those with syncope, but the etiologies are similarly distributed 3

Near-syncope represents an important warning sign that should prompt appropriate evaluation to identify potentially serious underlying conditions, particularly those of cardiac origin which carry significant mortality risk.