Physiology and Pathophysiology of Syncope Flashcards
Syncope
A specific form of transient loss of consciousness due to cerebral hypoperfusion, characterised by rapid onset, short duration and spontaneous recovery
Types of syncope
Reflex, cardiac and orthostatic
Transient Loss of Consciousness
A state of real or apparent loss of consciousness with loss of awareness, motor control. Short duration and results in amnesia
Types of reflex syncope
Vasovagal
Situation
Carotid Sinus
Causes of TLOC
Head trauma
Syncope
Epileptic seizure
TLOC mimics
Initial evaluation of TLOC
History
Full physical examination
Orthostatic BP measurement
12-lead ECG
Reflex syncope
All types of syncope in which neural reflexes modify HR (cardioinhibition) and/ or vascular tone (vasodepression), hence predisposing to a fall in MAP of sufficient severity to cause a transient period of cerebral hypoperfusion causing syncope/ near syncope
Which type of syncope is the most common?
(vasovagal) reflex syncope
What happens when reflex pathways are activated?
cardioinhibition via vagal stimulation-> bradycardia and decreased CO
Vasodepression via reduced sympathetic activity to blood vessels> decreased SVR, venous return, SV and CO
MAP decreases as CO and SVR falls-> cerebral hypoperfusion->syncope/ near syncope
What triggers vasovagal reflex syncope?
emotional or orthostatic stress
Symptoms of vasovagal reflex syncope
Typical prodrome (pallor, sweating, nausea)
How to avoid vasovagal reflex syncope?
increase venous return by crossing legs or adopting horizontal gravity neutralisation position
Risks of vasovagal reflex syncope
Injury when falling
* not associated with increased mortailtiy
Treatment for vasovagal reflex syncope
education
reassurance
avoiding triggers
adequate hydration
Situational reflex syncope
Faint during or immediately after a specific trigger eg coughing
Treatment of situational reflex syncope
treatment of cause eg cough
lie down
hydrate
cardiac permanent pacing
Carotid Sinus Reflex Syncope
Triggered by mechanical manipulation of neck, tight collar etc.
eg after head and neck surgery
Common in elderly (esp males)
Associated condition of carotid sinus reflex syncope
Carotid artery atherosclerosis
Treatment of carotid sinus reflex syncope
Permanent cardiac pacing
Cause of postural/ orthostatic hypotension
Failure of baroreceptor responses to gravitational shifts in blood when moving from horizontal to vertical position
Risk factors for postural hypotension
Age
Medication
Reduced intravascular volume
Prolonged bed rest
Positive result for postural hypotension
Drop within 3mins of standing from lying position:-
- in SBP of at least 20mmHg (with or without symptoms)
- in DBP of at least 10mmHg (with symptoms)
Symptoms of postural hypotension
Lightheadedness, dizziness, blurred vision, falls
Cardiac syncope
Syncope caused by a cardiac event which results in a sudden drop in CO
Causes of cardiac syncope
Arrhythmias
Acute MI
Structural cardiac disease
Other CVD eg PE
Features suggesting cardiac syncope
Presence of structural cardiac abnormality
Family history of sudden death at a young age
Palpitations followed by syncope
Syncope during excretion or when supine
