Definition

• Other terminology neurally-mediated reflex syncope
• Most common cause of syncope (especially young individuals)
  • F > M
• A heterogeneous group of conditions in which cardiovascular reflexes that are normally useful in controlling the circulation become intermittently inappropriate in response to a trigger resulting in vasodilation (vaso-depression) and/or bradycardia (cardio inhibition) and hence a fall in BP
• The normal increased sympathetic tone replaced by increased vagal tone

Classification

• Neuro-cardiogenic syncope - classified according to afferent pathway
  • Situational
    • specific situation acts as a trigger
      • cough, sneeze
      • gastro-intestinal: postprandial/swallow
      • post-exercise
      • micturition
  • Vasovagal/common faint
    • Orthostatic stressor
      • triggered by prolonged orthostatic stress
      • vasoconstrictor capacity is limited
        • blood pooling in periphery
    • Psychological stressor
      • witnessing distressing accident
      • pain
      • instrumentation
      • blood phobia
      • unpleasant smell
  • Carotid sinus hypersensitivity
    • external pressure on carotid bodies leading to symptomatic bradycardia (especially elderly, male predominance)
      • head turning
      • shaving
      • tight collar
    • 8% of elderly subjects with unexplained syncope
• Classification based on efferent pathway
• 
  • Type I - mixed type (most frequent)
    • Drop BP before fall in HR and
    • Drop HR

      • 40 bpm

      • < 40 bpm for <10s without asystole
      • < 40 bpm for <10s with asystole <3s
  • Type II - cardioinhibitory type: due to bradycardia or asystole
    • Drop HR
      • Type 2a: <40 bpm for > 10s without asystole but BP falls first
      • Type 2b: Asystole > 3s - decrease in HR before or coincides with fall in BP
  • Vasodepressor type: due to loss of upright vasoconstrictor tone
    • Drop BP < 60mmHg
    • HR does not fall more than 10% from its peak value

Hints in Diagnosis of Reflex Syncope

• Prodromes: Frequent
  • almost always (i.e. autonomic symptoms) short (i.e. < 60s before fainting)
    • nausea or vomiting
    • feeling cold or clammy, pale
• Trigger
  • unpleasant sight, sound, smell or pain
  • Prolonged standing
  • Hot crowded places / hot places
  • Carotid sinus pressure: head turn, tight collar
  • After exertion
  • During or after heavy meals
• +/- slow fall (collapsed) from an upright position
• Short duration: 1-30 seconds
• Long history of recurrent syncope, in particular occurring before the age of 40 years
• Recovery: quickly oriented, but sometimes with persistence of nausea, pallor and diaphoresis in addition to a prolonged fatigue (minutes/hours)

Diagnosis

Tilt Testing

• Aim: INDUCE reflex syncope in patients with unexplained TLOC
• Practical:
  • Fasted 4 hours prior to test
  • Pre-test phase of 5 minutes
    • Cannulation
    • Baseline measurements
  • Tilt angle: 60°
  • Passive phase: 45 min standing – continuous monitoring of ECG and BP until LOC or 45 min
  • Presence of cardiologist

Utility of the Tilt Test in 2025

Treatment

• Reassurance of benign condition – learn to live with it
• Education & counselling = cornerstone
  • Awareness and avoidance of triggers: use of cognitive behavioral therapy can be considered
  • Avoidance of agents that lower BP (alpha-blockers, diuretics, alcohol)
  • Salt intake: 2g
  • Water intake: 2-2.5l/day
  • Moderate exercise training
  • Sleeping 30° head up tilting
  • Early recognitions of prodromal symptoms (tilt-test can help to teach recognizing symptoms)
    • Lying down
    • Physical counterpressure manoeuvres
      • Leg Crossing
      • Hand gripping
      • Arm tensing
        • isometric contractions
          • increase BP
          • increase cardiac output