Syncope Flashcards
Describe syncope and other related conditions that temporarily impair consciousness
Syncope
- Syncope: sudden and brief loss of consciousness associated with loss of postural tone –> recovery is spontaneous
- Pre-syncope: sensation of light headedness, preceding syncope
- Orthostatic hypotension:
- drop in systolic BP >= 20 mmHg or
- diastolic BP >= 10 mmHg or
- MAP >= 10 mmHg
from lying to standing within 3 minutes
- transient ischaemic attack (TIA): temporary interference of blood supply to brains, resulting in symptoms of focal neurological deficit (e.g. monocular blindness, hemiparesis, speech disturbance, paraesthesia etc.) which resolve within 24 hours
Define syncope, and describe causes of syncope
Syncope is defined as transient loss of consciousness.
It is the result of inadequate cerebral perfusion with oxygenated blood.
It is relatively common and constitutes 5% of acute medical admissions.
Syncope is serious if it is secondary to cardiac causes: the one-year mortality rate is 20-30%.
Causes:
- neurallu mediated
- orthostatic
- cardiac arrhythmias** **
-cardiac structural: ischaemia, HOCM
- 10% idiopathics
NB: haemorrhage and PE
What is NOT syncope?
Several conditions are not considered syncope. These include:
- epilepsy and seizures
- TIA
- cardiac arrest where there is no spontaneous recovery
DIZZY means a lot of different things:
- hypotension: presyncope (orthostatic)
- epilepsy
- anxiety and hyperventilation
- ataxia and unsteadiness
- metabolic disturbance
- vertigo: central and peripheral
- physiological: motion sickness, height vertigo
Describe classification of syncope
- neurally mediated: vasovagal, carotid sinus, situational (60%)
- orthostatic: drug-induced, volume depletion, autonomic failure (15%)
- cardiac arrhythmias: bradyarrhythmias, tachyarrhythmias, channelopathies (10%)
- cardiac structural: AMI, aortic stenosis, HOCM, PE, PHT (5%)
- undetermined cause: 10%
List cardiac causes of syncope
Arrhythmias:
- sinus node dysfunction
- supraventricular tachycardia
- ventricular tachycardia
- channelopathies e.g. long QT, Brugada syndrome
Structural:
- AMI
- valvular disease (aortic stenosis)
- obstructive cardiomyopathy
- atrial myxoma
- constrictive pericarditis
- pulmonary embolus
Describe causes and triggers of neurally mediated reflex syncope
- vasovagal attack e.g. emotional, common faint
- carotid sinus syncope
- neurocardiogenic syncope
- increased intrathoracic pressure e.g. cough, sneeze, trumpet player, Valsalva induced
- post-micturition syncope
- GI stimulation — defecation, rectal examination
- oesophageal stimulation
Triggers for neurally mediated syncope:
- central: emotional stimuli e.g. fright
- postural: prolonged upright posture e.g. assembly
- situational: specific stimuli e.g. micturition
Describe the pathophysiology of syncope
- Transient and acute cessation of cerebral blood flow to reticular activating system — which controls consciousness
- cerebral perfusion pressure is associated with systemic arterial pressure (systemic arterial pressure = CO x Peripheral vascular resistance)
~ Decreased venous return ~
due to:
- hypovolaemia:
- dehydration
- bleeding
- diuretics
- other fluid loss
- impaired venous tone:
- autonomic neuropathy
- vasodilating drugs
- sepsis
~ Decreased cardiac output ~
due to:
- pump failure:
- valvular disease
- pulmonary embolus
- myocardial disease
- pericardial disease
- arrhythmia:
- tachycardia
- bradycardia
- (drugs)
~ Decreased cerebral perfusion ~
- afterload reduction:
- vasodilating drugs
- AV malformation
- Paget’s disease
- impaired cerebral circulation:
- atheroma
- vasculitis
Describe the mechanism of ssyncope in neurally mediated
- Afferent pathway not well understood
- in cats, hypercontractile, empty left ventricle sends paradoxic impulses to brainstem; response is transient, widespread sympathetic withdrawal
Describe syncope in the older adult*
Syncope in the older adult
- age-related impairment in: cerebral blood flow and autoregulation, heart rate, blood pressure, baroreceptor sensitivity
- co-morbidities e.g. diastolic dysfunction
- susceptibility to reduced blood volume
- concurrent medications e.g. anti-hypertensives
N.B.
Age-related increase in orthostatic hypotension prevalence (increases with age).
List possible differential diagnoses of syncope
- epilepsy or seizure
- vertigo: Meniere’s disease, or BPPV
- metabolic disturbance: hypoglycaemia, phaeochromocytoma, hypocalcemia
- anxiety/hyperventilation
- psychiatric:
- non-epileptic attack
- hysterical fugue state
- malingering
- other neurological conditions
- TIA
- migraine
- sleep disorder
- narcolepsy/sleep paralysis
*How to distinguish between differential diagnosis - history
The syncope history
1. precipitant
- pain, micturition, defecation, stressful event –> neurally mediated
- exercise or exertion –> cardiac
- posture –> orthostatic hypotension
- medications –> neural/orthostatic/cardiac
- meals –> postprandial hypotension
- premonitory symptoms
- sweating, nausea, abdominal cramps are suggestive of vasovagal and neurally mediated syncope
- chest pain, dyspnoea, palpitations are suggestive of cardiac syncope
- aura are suggestive of epilepsy
- associated features (Witness account)
- pallor
- absent or slow pulse
- incontinence if bladder full
- rhythmic movements of limbs or body (myoclonic jerks or clonic movements)
- postdromal symptoms
- amnesia to event
- nausea and vomiting
- rapid recovery
- post-ictal confusion
Past Medical History
- cardiac disease: ischaemic heart disease, arrhythmias, valvular disease = cardiac syncope
- neurological disease: Parkinsonism –> orthostatic hypotension, stroke, epilepsy
- diabetes: hypoglycaemia, orthostatic hypotension
- psychiatric history and mood
- risk factors for thromboembolic disease: pulmonary embolus
##### Venous return
- hypovolaemia: diuretics
- impaired venous tone: vasodilating drugs (nitrates, CCBs)
Cardiac output
- pump failure: cardiac drugs
- arrhythmia: prolonged QT interval (antihistamines, antibiotics, anti-arrhythmics, antifungals, psychotropics); bradycardia (digoxin, beta-blockers)
Cerebral perfusion
- afterload reduction: vasodilating drugs (nitrates, CCBs)
- impaired cerebral circulation
Family and social history
- sudden death
- vascular risk factors: family history of heart disease, smoking, obesity, diabetes, hypertension
- ethnicity
~ always obtain a collaborative history ~
..including the ambulance account
