Posts Tagged ‘afferent for neural syncope’

A strong willed  person rarely develop syncope.  We know  weak hearted (Or is it weak brained ?)   men and women may  faint  when  the emotions swing unexpectedly  .The  commonest cause of syncope is  neuro-cardiogenic  syncope (NCS) . (Formerly  called as  vaso-vagal syncope  VVS ). Few facts need to be  emphasized  here . There are  many  critical  circuits  and components to  common syncope.

  1. Trigger
  2. Afferent
  3. Center
  4. Efferent
  5. Fall /Near fall
  6. Prompt recovery after the fall.

Trigger can be emotional or mechanical (Prolonged standing ,  dehydration , etc )  . It occurs generally  in an emotionally  charged  environment with a high  basal sympathetic tone .

Afferent for  NCS   is  mostly sympathetic but it can be  para- sympathetic also (Sensitive GI tract ,  Micturition etc )

* Many times a  trigger and afferent pathway can overlap with each other.It is still unclear what exactly constitutes the afferent , since  triggers can be either sympathetic or para- sympathetic .  ( Pain, GI stimuli, vascular puncture etc) .  Further , afferent  can be be same as the trigger and reach the brain  stem directly  or touch  the heart en route .  ( Cardiac axis  in classical NCS)

The  center is  in the medulla  . Both vagal and sympathetic centers  are involved with potential  spill over on either side.

Final efferent  pathway is the strong  vagal surge resulting in bradycardia and peripheral vasodilatation , cerebral hypo-perfusion  and the person usually falls .( Near fall or aborted NCS  is also a common theme )

                                        If stress increases the blood pressure , absence  of stress  will have to  lower the blood pressure . If anxiety cause hypertension  ,  depression is expected to   cause hypo-tension.

These  inferences  may  appear  correct by logic . As  is always in medicine ,  such   logic works only partially ! ( We are told  the  Sadhus of Himalayas rarely record  blood pressure  beyond 100mmhg systolic  !)

There are strong reasons to believe common syncope (NCS)  is primarily related to the state  of mind and  the neural regulation. Dizziness ,  giddiness  near syncope  are closely related  to  psycho-somatic disorders. Strong willed men and women rarely develop   syncope.Their vascular   tone is well in control even in critical times .This fact has been  well observed  in  the setting of   traumatic  and hemorrhagic   shock  in critical care units  ,  where  some  hold their blood pressure well  even in   adverse circumstances  and few sink without any fight .

Is psychogenic , situational , pain syncope  same as NCS ?

Technically it may not be same. But all of  them  share at least 50 % 0f the  circuits of  NCS.  .However  there is no consensus  to call  psychogenic and   pain syncope  as  types of  NCS.

One critical aspect of  the debate is ,  we do not know whether the  cardiac axis is involved in these  syncope or not. It is preferable to call these types of syncope  as neural syncope (NS)

While in the classical NCS  heart has a  central role in generating hyper active sympathetic afferent from  myocardial stretch receptors. In psychogenic and pain syncope cardiac stretch receptors  are not much stimulated instead ,  the  spillover occur  directly from sympathetic to parasympathetic  nucleus in medulla.

In pain induced syncope parasympathetic limb  gets vigorously stimulated in isolation  to cause a severe  vaso-dilatation  . But once the syncope sets in we often observe bradycardia  and cardiac  limb may get activated as well.

* Presence or absence of cardiac limb in NCS and NS is critical with reference to efficacy of  beta blockers in NCS. The current guideline of NCS  management(  ESC 2010) is strongly biased against beta blocker (Class 3 -level A)  which we feel is  incorrect . Bulk of the patients with NCS respond well to long term beta blockers  .

Please realise , beta blocker  is the only drug which  can break the  NCS  circuit at multiple levels .(Sympathetic trigger, sympathetic afferent, cardiac stretch !

So what is the message ?

It doesn’t require great brains  to realise  vascular  and neural system are  intimately linked  . We know today,  NCS  is primarily a neural phenomenon  hence the  mental status has a  dominant  control over the vascular system especially at times of stress .

The confusion between classical  NCS and psychogenic  / situational  syncope can be largely avoided  , if  only  we call these entities  as simply neurogenic / neural syncope (NS ) ( Omitting the word cardiac is helpful ,   as cardiac axis is not vital  here  ? Non existent  )

Clarity is still  elusive  in defining the  trigger  and afferent limb for the NCS  , fortunately  the final common  efferent pathway that makes the patient fall is indisputably   vagal  !   .  Medullary  vagal nucleus  though fires independently  , also gets  powerful central  parasympathetic flow  from  cortical areas  . Paradoxically ,   controlling sympathetic outflow (Anxiety ) is often an easier  way to reduce parasympathetic flow. This is referred  to as competitive , accentuated  antagonism.

One can prevent recurrent  syncope  by vigorous  mind  control at times of  extreme stress. This is  confirmed  indirectly , by the fact  reassurance is the key to successful  management  in vast majority of  patients with NCS .We learnt this  simple fact  after trying exotic methods like DDDR pacing  and so on .

Final message

Power of  the mind can never be under estimated even in cardio- vascular hemodynamics .  When  pathologically high,   it can spike the blood pressure and break  few vessels in brain , while  if it  is inappropriately  low ,  may induce a syncope or result in persistent  hypo-tension .

Let us learn to use  our  mind over  body  properly .Yogis do it style  and live for 100 years !





Iam surprised why this post has been looked so negative by the readees. Almost all  rated it  as very poor.

Iam still pondering over it. Realised to lable patients as weak minded could be one of the reasons.

I think what I wanted to convey was there is link between mind and vascular system.

Please let me what is seen as offensive, let me learn and correct in future.







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