1- syncope overview & pathophysiology Flashcards
what is the definition of transient loss of consciousness (TLOC) ?
state of real or apparent loss of consciousness with loss of awareness, characterized by amnesia for the period of unconsciousness, loss of motor control, loss of responsiveness and a short duration
what conditions can TLOC result from?
- head trauma
- syncope
- epileptic seizures
- TLOC mimics (e.g. psychogenic, pseudo-syncope)
- other causes
*careful history must be obtained from a patient & witnesses
what is definition of syncope?
transient loss of consciousness due to cerebral hypoperfusion, characterized by rapid onset, short duration, and spontaneous complete recovery
what are 3 categories of syncope?
- reflex syncope
- orthostatic hypotension
- cardiac syncope
what is reflex syncope?
this is preferred terminology for ALL types of syncope in which neural reflexes modify heart rate (cardio-inhibition) and/or vascular tone (vasodepression)
- hence predisposing to a fall in mean arterial blood pressure (systemic hypotension) of sufficient severity to affect cerebral perfusion causing a transient period of cerebral hypoperfusion resulting in syncope or near syncope
what happens in reflex syncope?
- pathways for reflex activation not fully understood
- when activated, the reflex causes cardio-inhibition through vagal stimulation. This decreases heart rate (bradycardia) and cardiac Output CO
- And/or vaso-depression through depression of sympathetic activity to blood vessels. This decreases systemic vascular resistance (Vasodilatation), venous return, stroke volume and CO
- The decrease in CO and SVR, decreases mean arterial blood pressure (MAP)
- Resulting in cerebral hypoperfusion and syncope or near syncope
what are the different types of reflex syncope?
- vasovagal syncope (VVS)
- situational syncope
- carotid sinus syncope (CSS)
what is vasovagal reflex syncope?
- most common
- triggered by variety like emotional distress (pain or fear) or orthostatic stress (standing for long time etc)
- associated with typical prodrome (pallor, sweating, nausea)
how can vasovagal reflex syncope be averted?
can be averted e.g. by adopting horizontal gravity neutralisation position or leg crossing (these increase venous return)
what is the main risk for vasovagal reflex syncope?
risk of injury when falling
- not associated with mortality
what is the treatment for vasovagal reflex syncope?
education, reassurance, avoidance of triggers and adequate hydration
what is situational reflex syncope?
- faint during or immediately after specific triggers e.g. cough, micturition (urine), swallowing etc
- less common than vasovagal syncope
what is the treatment for situational reflex syncope?
treat cause of possible (e.g. cough), advise patient to lie down if possible, avoid dehydration & excessive alcohol, cardiac permanent pacing may be needed in some cases (might be impossible to avoid some causes)
what is carotid sinus reflex syncope?
- triggered by mechanical manipulation of the neck e.g. shaving, tight collar etc
- more common in elderly especially males
- other associated conditions such as carotid artery atherosclerosis may be found but not clear causative
- CSS may occur after head & neck surgery or radiation
what is treatment of carotid sinuses reflex syncope?
cardiac permanent pacing generally recommended
what is postural hypotension syncope?
results from failure of baroreceptor responses to gravitational shifts in blood when horizontal → vertical
what are risk factors of postural hypotension syncope?
- age related
- medications
- certain diseases
- reduced intravascular volume
- prolonged bed rest
what indicates a positive postural hypotension?
positive result is indicated by a drop with 3 minutes of standing from lying
- systolic from at least 20mmHg (with or without symptoms)
- diastolic from at least 10mmHg (with symptoms)
what are symptoms of postural hypotension?
- lightheadedness
- dizziness
- blurred vision
- faintness
- falls
what is cardiac syncope (and what’s caused by)?
= caused by cardiac event resulting in sudden drop in cardiac output
caused by:
- arrhythmias (causing bradycardia & tachycardia)
- acute MI
- structural cardiac disease e.g. aortic stenosis, hypertrophic cardiomyopathy
- other cardiovascular disease e.g. pulmonary embolism, aortic dissection
what should initial evaluation for syncope be?
- very careful history (from patient & any witnesses)
- full physical examination including
- orthostatic blood pressure measurement
- 12 lead ECG
*additional examination & investigation then be planned based on findings from above
what are some features that suggest a cardiac syncope?
- syncope during excretion or when supine
- presence of a structural cardiac abnormality or coronary heart disease
- a family history of sudden death at young age
- sudden onset palpitations immediacy followed by syncope
- findings on ECG suggestive of arrhythmic syncope
