Syncope Flashcards
Define syncope
transient loss of consciousness due to global cerebral hypoperfusion
3 features of syncope
rapid onset
short duration
spontaneous complete recovery
What causes transient loss of consciousness?
Traumatic - head injury
Non-traumatic:
- global cerebral hypoperfusion (syncope)
- not due to global cerebral hypoperfusion (epilepsy, psychogenic, hypoglycaemia, hypoxia, toxins, subarachnoid haemorrhage, vertebrobasilar TIA)
Causes of syncope
reflex
orthostatic
cardiac
unknown
What are the 3 types of reflex syncope?
vasovagal
situational
carotid sinus syndrome
What ages does reflex syncope affect?
any age (more common in younger + elderly)
What does reflex syncope occur in response to?
a trigger
- emotional stress or real/threatened/imagined injury (eg. due to pain, sight of blood)
What position is reflex syncope most common in?
standing up
What are the symptoms just before a syncopal episode?
usually a prodrome lasting 30 secs - several mins
fatigue
yawns
hot
sweaty
nauseous
dimming of vision
How does a patient appear during a syncopal episode?
pale
diaphoretic
How does vasovagal syncope occur?
pain/emotional trigger
exaggerated sympathetic activation
circulating hypovolaemia
activation ventricular afferents
brainstem:
- sympathetic withdrawal –> vasodilation –> hypotension –> syncope
and/or
- increased vagal tone –> bradycardia –> syncope
Common triggers of vasovagal syncope
pain
fear
prolonged standing
having blood taken
What is situational syncope?
a form of reflex syncope caused by specific triggers
micturition syncope = fainting occurring shortly after or during urination
mainly occurs in men
some triggers = micturition, defaecation, coughing, laughing, swallowing
Describe the carotid sinus reflex
carotid sinus = a dilatation at the base of the internal carotid artery that contains baroreceptors which monitor BP
increased BP = stretches carotid baroreceptors = send messages to brain stem:
- increase parasympathetic activity (decrease HR + contractility), decreases CO, decreases BP (BP = TPR x CO)
- decrease sympathetic activity (vasodilatation), decreases total peripheral resistance, decreases BP
What is carotid sinus massage and what is a normal response?
bedside test to test the carotid sinus reflex
normal response = slight drop in HR and/or BP
exaggerated response occurs in carotid sinus sensitivity
What is carotid sinus syndrome?
syncope without warning and exaggerated carotid sinus massage response with reproduction of syncope
mainly in older men
pacing can help if carotid sinus massage mainly causes bradycardia
Carotid sinus syndrome triggers
head turning
shaving
tight collars
What is orthostatic hypotension?
standing from a supine position causes roughly 10-15% blood volume to be redistributed to the abdomen and lower limbs, reducing venous return and cardiac output
without compensatory mechanisms, BP would drop
can cause syncope, dizziness on standing or falls
How is orthostatic hypotension defined?
decrease in systolic Bp of >=20mmHg (or diastolic >=10mmHg) within 3 mins of standing
OR
decrease in systolic BP <90mmHg
What is the normal physiology of orthostasis
decreased stretch of carotid sinus
decreased baroreceptor traffic
increase sympathetic activity
decrease parasympathetic activity
increased vasoconstriction
increased HR
increased contractility
What drugs can make orthostatic hypotension more likely?
anti-hypertensives
anti-anginals
anti-BPH (benign prostatic hyperplasia)
anti-depressants
anti-psychotics
anti-parkinsonian
alcohol
What are some causes of hypovolaemia that can make orthostatic hypotension more likely?
dehydration
Addison’s disease
What causes of autonomic failure can make orthostatic hypotension more likely?
primary = Parkinson’s
secondary = aging, diabetes
What features suggest orthostatic hypotension?
symptoms are worse:
- on standing
- in the morning
- after meals
- after exercise
- in hot environments
symptoms are better:
- when lying/sitting
Management of reflex syncope and orthostatic hypotension
reassurance
education
lifestyle changes
stop/reduce BP lowering drugs
still symptomatic = counter-pressure manoeuvres
selected patients:
- low BP = fludrocortisone, midodrine
- slow HR = pacing
When should pacing be considered for syncope?
recurrent syncope despite medical therapy
+ bradycardia or asystolic pauses
What causes cardiac syncope?
arrhythmia:
- bradycardia = sinus node disease, AV block
- tachycardia = VT, SVT
structural:
- cardiac = aortic stenosis, ACS, cardiomyopathy
- vascular = PE, aortic dissection
Syncope red flags
symptoms:
- on exertion
- supine
- no warning
PMH:
- structural heart disease
- coronary artery disease
- heart failure
FH:
- sudden cardiac death
other symptoms:
- chest pain
- palpitations
- SOB
- abdominal pain
- headache
examination:
- low BP
- slow HR
- undiagnosed systolic murmur
abnormal ECG
Key points in a syncope history (6Ps)
provoking factors
posture
prodrome
PMH/DH/FH
Passerby account
Post event
Key points in examination in syncope
heart rate - rate + rhythm
lying + standing BP
carotid sinus massage
systolic murmur (aortic stenosis, hypertrophic cardiomyopathy)
What investigations can be carried out for syncope?
ECG
ECHO - if structural heart disease suspected
Cardiac rhythm monitoring:
- Holter - frequent symptoms + arrhythmic cause suspected
- Loop recorder - infrequent cause and arrhythmic cause suspected
Tilt Test - syncope of unknown cause where reflex syncope is suspected
