Recently , I came across a young women who underwent the following three tests for one episode of syncope after witnessing her pet dog bleeding with an Injury !
- Carotid doppler
- Holter monitoring and event monitors
- Brain MRI /MR angiogram
This was followed up by Head up tilt(HUT) in a premier hospital
After 1 week of investigation ,a diagnosis of Neurocardiogenic syncope was made and she was reassured and no drugs were prescribed.
(The collective yield of the above three investigation in fixing a specific diagnosis is less than 10 % of all known causes of syncope )
To diagnose common syncope . . . we need common sense !
Syncope is a dramatic symptom.It is one of the commonest symptom in ER as well . Life time incidence of syncope is at least one episode in 50% all human life ! The definition of syncope until recently , was liberal .Any transient loss of consciousness with spontaneous recovery was termed syncope.
This includes
- Hypoglycemia
- Anemia
- Siezure disorders
- Structural neurogenic (Including , brain tumors , Dural hematomas etc )
- Panic attacks (psychogenic)
Cardiologists wanted to fix syncope as an exclusive disorder of circulatory insufficiency.By bringing in a modification in the definition , ie syncope is now defined as a transient loss of consciousness due to reduction in cerebral perfusion .
This definition helped cardiologists to exclude the above entities . Still many would include all in single basket as patient should be seen as a whole and we can’t expect them to land according to our convenience and classification.
Here is an incomplete* list about causes of syncope (* 99% complete ?)
Vascular
- Vaso- vagal syncope in young ( Neuro-cardiogenic , Common , Benign)
- Autonomic dysfunction of elderly ( Including postural hypotension )
Cardiac
Arrhythmic ( Sinus node dysfunction /CHB/Idiopathic VT/Long QT syndromes)
Structural heart disease
- Valvular heart disease (LVOT/RVOT obstructions)
- Myocardial disease
- Rarely ischemic heart disease
Miscellaneous
- Severe pulmonary hypertension (Including PPH , pulmonary Embolism )
- Paradoxical embolism.
- Aortic arch disease -Takayasu related arteritis .
Investigation
We have a sophisticated array of investigation for syncope .It can be a never ending exercise , ranging from spinal cord evoked potentials to diagnose Shy-drager syndrome , . . . to implanting long-term loop recorders to decode heart beat behavior.
However , evaluation of syncope is the ultimate wake-up call to all current generation cardiologists . . . Why clinical cardiology should never be allowed to die (and it will not ! )
Common sense begins with answering few simple questions . Is it really syncope ?
If you ask this question three times and with specific leads to the patient and the witness , truth will come out . 90% of times it may not be syncope at all (Near syncope, accidental fall, dizziness ,extreme blurred vision, drowsiness etc)
If it is syncope , Is there a non cardiac cause ?
It may related to the Hypoglycemia / Anemia /Panic attacks.Get a neurologist opinion , it would be terrible mistake if you miss a space occupying lesion within the brain. (Missing chronic silent sub dural hematomas is frequent in the evaluation of syncope of elderly !)
Ruling out cardiac syncope is relatively easy
In the remaining patients basic investigation like routine blood tests,ECG, ECHO will help us rule out most serious cardiac disorders.Similarly bulk of the electrical cardiac syncope can be diagnosed.(Holter , carotid study in selected few )
Need for neurologist -cardiologist interaction.
Syncope due to VBI, transient Ischemia attack , Senile vascular dementia is a grey zone . Many have complex neuronal -vascular mechanisms . What is Consciousness ? and What is LOC ? :Is it the lack of blood or severely depressed nerve signal in the reticular activating system? Lots of interaction between cardiologist and neurologist is required to clear our ignorance.(I have one such elderly patient who is intermittently awake ! I call this chronic syncope !) .
Undiagnosed syncope is not a crime
Realise the most important lesson in Medicine . If you have ruled out all serious causes of syncope you should have the courage to be satisfied with that !
Scientific pursuits has a limit. Searching for the mechanism of a psychogenic fainting attacks with intra cerebral electrodes is a clear case of physician acquiring a psychotic behavior !
Final message
Syncope is not only a dramatic symptom for the patient , it also unfolds a drama of costly investigations . . . many with dubious value.
Talk to the patient personally for 10 minutes in a quiet room, try to apply that elusive clinical sense . . . it would rarely let you down !
After thought
What is the true clinical value of * Head up tilt Test (HUT)?
Will be posted soon
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Dr.S.Venkatesan MD 