Approach to syncope

What is syncope?
Transient LOC with loss of postural tone (ie unconscious collapse) with spontaneous return to baseline
What is the mechanism of syncope?
Global hypoperfusion of both the cerebral cortices or focal hypoperfusion of the reticular activating system.
Broad causes of syncope
Neurocardiogenic (or reflex)
Does HR go up or down in neurocardiogenic syncope?
Down (it's usually a vaso-vagal response - mediated by parasympathetics)
Does HR go up or down in orthostatic syncope?
Causes of orthostatic syncope?
1. Primary Autonomic failure (for example, Parkinson's Disease)
2. Secondary: autonomic peripheral neuropathies - (common in diabetes)
3. Iatrogenic
4. Volume depletion
Causes of cardiac syncope?
1. Arrhythmias: eg. bradycardia, VT, brugada and other inherited chanelopathies...pacemaker dysfunction
2. Structural issues: eg. HOCM, valvular disease
Principles of history-taking in syncope - what four parts of the story do you need to find out about?
Background (FHx, PHx)
What red flags on history are suggestive of cardiac syncope?
Background: risk factors
Before: exertional, chest pain, supine, no warning/prodrome
After: instantaneous recovery
What red flags on history are suggestive of seizure?
Background: PHx epilepsy, not taking medications, precipitants that lower seizure threshhold (eg. no sleep, alcohol withdrawal)
Before: prodrome
During: tonic phase before rhythmic, clonic activity, head deviation or unusual posturing during the episode, loss of bladder or bowel control
After: tongue biting, postictal confusion/disorientation (usually >30min)