syncope Flashcards
what is syncope
transient loss of consciousness due to global cerebral hypoperfusion; acute onset and spontaneous complete recovery
what systolic BP results in syncope
<70mmHg
what is the most common form of syncope
vasovagal syncope
causes of transient loss of conciousness (5)
traumatic;
non-truamatic - syncope, elipepsy, psychogenic, misc (e.g. metabolic, toxins, haemorrhage etc.)
how to distinguish syncope from other TLOCs
syncope - rapid onset, short duration, spontaneous, complete recovery;
others are not characterised by these
4 syncope categories
reflex (60%); orthostatic (15%); cardiac; unkown
3 types of reflex syncope
vasovagal; situational; carotid sinus syndrome
reflex syncope - what triggers it, warning signs, who it occurs in
occurs due to a trigger e.g. emotional stress, injury, pain etc.
warning - there is a prodrome which lasts 30s-several mins where the pt feels fatigued, sweaty, dimming of vision, ringing in ears;
occurs in younger pts
vasovagal syncope pathway
trigger (exaggerated sympathetic activation) leading to –> increased vagal tone/prarsympathetic stimulation –> bradycardia, vasodilation of peripheral blood vessels –> hypotension –> cerebral hypoperfusion –> loss of conciousness
common triggers of vasovagal syncope (5)
pain; prolonged standing; fear; dehydration; stressful events
symptoms of vasovagal syncope
dizziness; fainting; feeling warm; nausea; ringing in ears; tunnel vision etc.
what is situational syncope
a form of reflexive syncope caused by specific situational triggers
examples of situational syncope (5)
micturition; defaecation; coughing; laughing; swallowing
who does micturition syncope affect more and what is the mechanism
affects men - usually benign in young men but associated with comorbidities.postural hypotension in older;
occurs when stretch receptors innervate the brainstem which upregulates parasymp.
what is the carotid sinus reflex
the carotid sinus is a dilation at the base of the internal carotid artery that contains baroreceptors which monitor BP
carotid sinus reflex pathway (2)
- ↑ BP –> ↓ symp. –(vasodilation)–> ↓TPR –> ↓BP
- ↑ BP –> stretch carotic barorecptors –> message sent to brainstem –> ↑ parasymp – (↓ HR + contractility)–> ↓ CO –> ↓BP
what can be done to test the carotid sinus reflex
carotid sinus massage - a normal response is a slight drop in HR/BP, an exaggerated response indicates carotid sinus hypersensitivity
what is carotid sinus syndrome
syncope without warning and hypersensitive CSM response (and reproducable syncope w CSM)
carotid sinus syndrome triggers examples (3)
head turning; shaving; tight collar (too much pressure on CS)
what can help exaggerated CSM
pacing
what is orthostatic hypotension
a form of low blood pressure that happens when standing after sitting or lying down - compensatory mechanisms are required to maintain BP as blood volume is redistributed around the body
orthostatic hypotension definition (stats)
↓systolic BP >20mmHg within 3mins of standing or a systopic BP of <90mmHg on standing
How is the arterial blood pressure adjusted as someone stands up after being in a lying
position?
When someone stands up the venous return falls due to gravity, Cardiac input diminishes and
arterial BP is reduced (↓preload) => Baroreceptors afferent firing is reduced – medullary centres inhibition reduced -> ↑sympathetic tone to arterioles and veins (vasoconstriction), Reduced vagal tone to SAN =>
↑myocardial sympathetic tone –> ↑HR -> ↑stroke work –> ↑ blood pressure
what occurs when standing up when there is no compensation
↓venous return -> ↓underfilled LV -> ↓SV -> ↓CO -> ↓BP
causes of OH (3)
- drugs e.g. antihypertensives, antiparkinsonian, antianginals etc.
- hypovolaemia (dehydration, addison’s disease)
- autonomic failure - primary (Parkinson’s), secondary (ageing, diabetes)
when are OH symptoms worse
on standing; in the morning; after meals; after exercise; in hot environments
management of reflex syncope and OH (8)
reassurance; education; lifestyle changes; counter-pressure manouvers (e.g. squatting); increase fluid intake; reduce BP lowering drugs; pacing (select pts only); fludrocortisone (select pts only)
when is pacing considered in reflex syncope
recurrent syncope despite medical therapy + brady/asystolic pauses; only benefits those with bradycardia
what causes cardiac syncope
arrythmia (2/3) e.g. AV block, SVT; structural (1/3) e.g. AS, PE, HOCM
red flag symptoms for syncope (history/PMH -6)
history - exertion (AS, coronary ischaemia), supine, no warning;
PMH - structural heart disease, CAD, HF
red flag symptoms for syncope (FH, associated - 6)
FH - sudden cardiac death;
associated - chest pain, palpitations, SOB, abdo pain, headache
red flag symptoms for syncope (examination, ECG -8)
examination - low BP, bradycardia, undiagnoses systolic murmur;
abnormal ECG - long QT, brugada sign (or other channeopathies), conduction disease, arrythmia, acute MI
6Ps for syncope history
before - provoking factors, posture, prodrome, PMH (+DH,FH);
during - passerby account
after - post event (rapid recover etc.)
what is the tilt table test
a test used to provoke reflex syncope in a lab setting; pt starts off supine and gradually tilted to upright position –> +ve test will result in ↓systolic BP (vasodepressor) or ↓HR (cardioinhibitory) or ↓BP +↓HR (mixed)
why is the tilt table test rarely used
time consuming and it is a very artificial investigation
role of cardiac rhythm monitoring
if arrythmia is suspected and symptoms are frequent (holter) or infrequent (loop recorder)
