What is the definition of sleep syncope?

Definition of Sleep Syncope

Sleep syncope is defined as a form of vasovagal syncope that interrupts sleep, where patients experience syncope after awakening from their sleep. 1

Key Characteristics of Sleep Syncope

• Sleep syncope is a subtype of reflex syncope (vasovagal syncope) that occurs during normal sleep, often causing the patient to awaken with prodromal symptoms before losing consciousness 2
• The European Heart Association specifically identifies sleep syncope as a distinct clinical entity that can occur when a prodrome of vasovagal syncope causes awakening followed by syncope thereafter 2
• Unlike traditional vasovagal syncope which typically requires upright posture, sleep syncope occurs in the supine position during or immediately after sleep 3
• Most patients with sleep syncope (96.5%) also experience typical daytime vasovagal syncope episodes 4

Clinical Presentation and Associated Features

• Gastrointestinal symptoms are prominently associated with sleep syncope:

  • Upper gastrointestinal symptoms are present in 65.6% of patients 4
  • Lower gastrointestinal symptoms are present in 86.0% of patients 4
  • Abdominal discomfort is significantly more common in sleep syncope (80%) compared to classical vasovagal syncope (8%) 1

• Other distinctive features include:

  • Vagotonia is more frequent in sleep syncope patients (33%) compared to classical vasovagal syncope patients (2%) 1
  • History of phobias is reported in 67.6% of patients with sleep syncope 4
  • Childhood syncope and blood-needle phobia are significantly more common in sleep syncope patients compared to those with classical vasovagal syncope 1

Diagnostic Considerations

• A diagnosis of sleep syncope can be established when there is:

  • Clinical suspicion based on the characteristic presentation
  • Preserved left ventricular function without evidence of coronary artery disease
  • No high-risk electrocardiographic findings (pre-excitation, long/short QT syndrome, Brugada syndrome, or arrhythmogenic right ventricular dysplasia)
  • Normal neurological evaluation 3

• Head-up tilt testing is positive in approximately 90.9% of sleep syncope patients, similar to the positivity rate in classical vasovagal syncope 4

Clinical Course and Prognosis

• Despite the potentially alarming presentation of losing consciousness during sleep, the prognosis of sleep syncope is generally favorable 1
• Long-term follow-up studies (average 15 years) show:
  • Significant decrease in episode frequency from 1.9 ± 3 to 0.1 ± 0.3 episodes per year with appropriate management 1
  • Similar mortality rates compared to classical vasovagal syncope 1
  • Low rates of permanent pacemaker requirement (approximately 3%) 1

Common Pitfalls in Diagnosis

• The occurrence of syncope in the supine position may mislead clinicians to suspect more serious cardiac causes, as supine syncope is traditionally considered an alarm symptom 5
• The presence of gastrointestinal symptoms might divert attention from the syncopal event to potential gastrointestinal disorders 4
• The association with sleep may lead to confusion with sleep disorders or nocturnal seizures 2
• Clinicians should be aware that syncope can occur in all body positions, not just standing, and should consider sleep syncope in the differential diagnosis of loss of consciousness during sleep 6

Management Approach

• Most patients respond well to education and reassurance about the benign nature of the condition 1
• Treatment is generally similar to that of classical vasovagal syncope, focusing on identifying and avoiding triggers 1
• The American College of Cardiology and European Heart Association guidelines recommend a thorough evaluation to exclude other potentially serious causes of loss of consciousness during sleep 2