Unit 4 - Syncope Flashcards
what can cause transient losses in consciousness?
- nontraumatic (syncope, epileptic seizure, functional TLOC, rare causes/mimics)
- traumatic (concussion)
what is the definition of syncope? its requirements?
complete, transient loss of consciousness and postural tone
- rapid onset
- complete loss of consciousness and postural tone
- brief (30 sec to <5 min)
- spontaneous recovery
what is cerebral perfusion determined by? dependent on?
determined by BP, which is dependent on CO (contractility, blood volume, HR) and vascular tone (autonomic nervous system)
how much volume do the veins hold?
65% of total blood volume
what is special about arterioles?
they are resistance vessels with a wide range of tone and volume
what are determinants of CO?
SV x HR
- structure
- LV (end diastolic) volume
- HR
what does sympathetic system do for structure?
increased contracctility
- myocardial function (LV EF)
- hypertrophic obstructive CM / AS (outflow obstruction)
what can cause LV volume changes in syncope?
- hemorrhage
- renal/adrenal dysfunction
- dehydration
how does tachycardia cause syncope?
too little time for LV to fill –> low LV EDV –> decreased CO
- contraction (systole) time remains fixed irrespective of HR
- relaxation time decreases as HR increases
what does increased pooling of blood in extremities/mesentery do to CO?
decreases CO
what is the etiology of syncope?
- neurally mediated (vasovagal, carotid sinus, situational cough/post-micturation)
- orthostatic (drug-induced, ANS failure primary or secondary)
- cardiac arrythmia (brady sick sinus or AV block, tachy VT or SVT, long QT syndrome)
- structural cardiopulmonary (aortic stenosis, HOCM, pulmonary HTN)
5 non-cardiovascular (psychogenic, metabolic hyperventilation, neurological)
what is reflex/neurally mediated syncope?
abrupt withdrawal of sympathetic tone
- leads to vasodilation/hypotension and bradycardia
- vaso-vagal: stress, pain, phobia
- situational: cough, sneeze, laugh, eat/pee/poop
- carotid sinus hypersensitivity
what is orthostatic hypotension?
inadequate peripheral vasoconstriction in response to orthostatic stress
-drop in BP by 20/10 within 3 minutes of standing
causes of orthostatic hypotension?
DAAD (drugs, autonomic dysfunction, alcohol, dehydration)
- Drugs: diuretics, sedatives, psychiatric drugs, alpha-blockers (used in BPH)
- Primary autonomic failure: Parkinson’s multiple system atrophy, Lewy body dementia
- Secondary autonomic failure: diabetes, amyloidosis, spinal cord injury
- Alcohol
- Volume depletion: dehydration/diarrhea, hemorrhage
what is cardiac syncope caused by?
- bradycardia: drug-induced, electrolyte abnormality, conduction system disease
- tachycardia: VT or SVT
- HOCM (systolic murmur)
- aortic stenosis (systolic murmur)
- severe CHF (S3/4, lung crackles)
if you get syncope from sudden noise or extreme emotions, what is a likely diagnosis?
long QT syndrome
what is syncope prodrome?
- vasovagal: nausea/abdominal pain, dizziness, tinnitus, neck/shoulder pain
- -may be absent in elderly
- arrhythmia: none or very brief prodrome, palpitations
- seizure: deja-vu, hallucinations, sensory aura
what are questions to the witness?
- slump over or fall abruptly
- skin color (cyanotic, pale, flushed)
- any motor movements
- pattern of breathing
- duration of episode
- mental status post-event
- incontinence
what does syncope post-drome look like?
arrhythmia: rapid recovery
vasovagal: may take longer to recover
seizures: post-ictal confusion, neurological deficits
what should you look for on physical exam for syncope?
- vitals (supine/standing BP/HR)
- pallor
- neck (carotid pulse/bruit, JVP)
- cardiac (regulatory rate, murmurs)
- lungs (air entry, wheezing, crackles)
- neuro (deficits, mentation)
what labs should you order for syncope?
- CBC (hematocrit)
- BMP (Na/K, BUN/creatinine)
what are high risk features of syncope?
- exercise-induced
- FH of SCD
- “drop attacks”
- abnormal EKG
- pallor/anemia/electrolyte abnormality
what testing should you order for syncope?
- cardiac: echo, rhythm monitoring, EP study
- neurogenic: tilt-table testing if diagnosis is in doubt
- neurology: EEG, MRI
treatment for neurogenic/vasovagal syncope
- lifestyle modifications: avoid triggers, adequate salt intake/hydration, moderate exercise
- physical counterpressure: tight stockings, tilt training
- pharmacology: BB, fludrocortisone, alpha agonists, SSRI (paroxetine)
- permanent pacemaker: class IIb indication (“possibly useful”)
what is treatment for orthostatic hypotension?
- treat the treatable with drugs
- -midodrine (peripheral alpha agonist)
- lifestyle changes (adequate hydration, leg exercises before getting up)
- stockings
- aids to improve balance (cane, walker)
treatment for cardiac syncope
high risk and most easily treated
- brady: pacemaker
- tachy: ablation
- HOCM/aortic stenosis: surgery
- AICD
