Definition of Syncope
TRANSIENT
short duration; <5mins
UNRESPONSIVE
no response to speech/touch/pain. required witness.
UNAWARE
loss of memory.
UNCONTROLLED
fall, abnormal movement.
Conditions that may be misdiagnosed as syncope
| Cause of Loss of Consciousness |
Not syncope because... |
| Seizure | not from cerebral hypoperfusion |
| Trauma | not from cerebral hypoperfusion |
| Intoxication (from drugs, alcohol, and etc.) | not totally unaware, not from cerebral hypoperfusion |
| Cardiac Arrest | not transient, not reversible |
| Stroke | not transient |
| Subarachnoid hemorrhage | not from cerebral hypoperfusion
(consciousness may be progressively reduced rather than immediately lost. Accompanying severe headache, other neurological signs) |
| Cataplexy | not unaware (unresponsive, uncontrolled, but fully aware) |
Syncope is Transient Loss of Consciousness due to Cerebral Hypoperfusion.
Causes & Prognosis of Syncope
Red Flag Features
(People requiring urgent assessment and treatment)
- Abnormal ECG
- Heart Failure
- TLoC during exertion
- Family history of sudden cardiac death in people aged younger than 40 years and/or an inherited cardiac condition.
- New or unexplained breathlessness.
- A heart murmur.
- Consider referring within 24 hours for cardiovascular assessment, as above, anyone aged older than 65 years who has experienced TLoC without prodromal symptoms.
NICE Guidance on TLoC. Updated 2014.
Reflex syncope (or vasovagal, or neurally mediated) is the most common cause. Cardiac syncope has the worst prognosis.
Initial Evaluation
Initial evaluation includes detailed history taking, physical examination, and ECG.
History taking, if properly performed, is in most cases the only ‘test’ necessary.
Diagnostic Evaluation
Choice of Diagnostic Testing(s) is driven by the initial evaluation. The use of broad-based investigations is ineffective and costly.
Bifascicular Block
1. Chronic bifascicular block increases risk of complete heart block.
2. Earlier non-randomized date favors the EPS or Implantable monitoring guided approach, rather than empirical pacemaker.
3. In a recent data from an RCT, permenent pacemaker compared to implantable monitoring is a preferred strategy.
Exercise-related Syncope
1. Syncope DURING exercise is most concerning for cardiac etiology.
2. Syncope AFTER exercise is usually from reflex syncope or orthostatic hypotension.
Post-prandial Hypotension/Syncope
1. Postprandial hypotension/syncope is not uncommon in elderly esp. with comorbodities.
2. The major mechanism is likely orthostatic hypotension due to autonomic failure.
3. Though the mechanism is benign, the underlying comorbidities are not.
The Issues of Recurrency
1. Many patients have more than 1 etiology of syncope.
2. Syncope and Recurrent Syncope increase morbiditiy and mortality.
3. Syncope may be the 1st manifestation of a more severe underlying cardiovascular disease.
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