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Posts Tagged ‘wide qrs tacycardia’

Wide qrs tachycardia often  evoke a   OCD like reaction  among  many  cardiologists (Obsessive compulsive disorder).  Whenever we are given a strip of wide qrs tachycardia  we are compelled to initiate a  conscious or  subconscious debate , whether it is VT  or SVT . Tens of thousands of articles, seminars, CMEs , have been conducted for over 30 years  for  decoding  wide qrs tachycardias  . The fact that the confusion  is still widely prevalent indicate only two things

  1. Either , it is not possible to arrive at a simple fool proof  bed side modality  to confirm either VT or SVT
  2. Or it is a too trivial  electrophysiological   issue  that   need  not be worried about  as we have broad spectrum antiarrhythmics (Like antibiotics ! , where we  rarely  bother about identity of the culprit  bacteria  )

The power of statistics and commonsense have never been applied  in the management this vital cardiac entity  .While a  75% sensitive  exercise  stress test (EST) has a huge following in clinical cardiology , a   99 % sensitive   clinical criteria*  for diagnosing VT is  not respected .

*All wide QRS  tachycardia  in patients with   with history of   CAD/STEMI would be VT

If only we had applied our mind to this article published in 1988 we will never ever have the need to split our hairs for decades.(That too without success !)

In  pursuit of  knowledge , are we often  chasing  an imaginary  issue ?

The cardinal  principle of medicine says

“Diagnosis should precede treatment  whenever possible

But there need to be a correction  in the above statement .  Time , effort , cost involved in arriving at a  diagnosis  should be meaningful .( Needless to say  . . . it should  a correct diagnosis  too ) And if the power of statistics far exceeds the  frivolous scientific data  , street sense can be applied  liberally even though current generation may call it un scientific .

The issue here is  not being  scientific or unscientific , but whether you are right or wrong  . The article  which is quoted here  has a great insight  about the philosophy of VT diagnosis.

The message form this article goes something like this . . .

In the diagnosis of  wide qrs tachycardia , If we apply  the so called scientific principles   the chances  for missing   a real VT is extraordinarily high , while  if you blindly apply common sense and logic you are going to be 90% right .

What a powerful  statement this !  even though it appears  absurd ,  it is absolutely true !

A young physician  should realize the importance of this . Scientific  decoding of arrhythmia  may be an academic  pursuit but in a given patient at bedside  diagnosing by experience and common  logic are  far more productive and accurate. Miss diagnosis of VT was not common prior to 1980s .  It has become a recent phenomenon .

Probably too much of electrophysiology haS  made a simple diagnostic pathway a complex one. When we relied only on commonsense the errors were less . I  have  often observed  fellows  making mistakes quite frequently  while  nurses  were too confident  to call a wide qrs tachycardia   as VT .

Final message

Medical decision making is an art , in fact it is  a “fine art ”   We keep saying this for centuries , still medicine as a  science  easily overtakes medicine as an art. Here comes the problem . Some times (or is it many times ! ) too much of inquisitiveness in the   name of  science  make practice of medicine  complicated and the victims are often the patients !

Let us simplify medicine  . . . let us accept an occasional  bad outcome  . . . for not being 100 % scientific  ! After all  , a million mistakes happen every day in the  pure  scientific  pathway .

Reference

http://www.amjmed.com/article/0002-9343(88)90008-3/abstract

Also read Knowledge disease

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Traditionally we believed VT can originate only  from the ventricular myocardial cells . Then we realised many of the VTs shared the characteristics of SVT. When these were analysed , it was found VTs , after all ,   do not have   a big deal of   difference wth SVT s ! especially when it arises from the high septum .Contary to the conventional teaching  the AV node is not a anatomically distinct and discrete  structure  .Instead it is made up of  thousands of specialised cells located in AV junctional area .These cells ramify both superiorly and inferiorly like an octopus . Hence  , it does not require great academics to understand AV Nodal properties extend downward into the IVS for some distance . In some individuals   clusters of cells with  slow conducting  property (Which is a hall mark of AV nodal tissue )  may invade deep into the IVS .The interface of  these slow conducting tissue with that of  fast septal purkinje fibres , make it a  perfect platform for  the potential slow-fast reentry within IVS. This forms the basis of fascicular  VT.

Clinical features

  • Since it shares the  properties of SVT , the natural history is also relatively beningn
  • Occurs in young
  • Hemodynamically stable ( More physiological conduction : Superi inferior Like SVT)
  • Narrow qrs (Narrow because the VTdoes not travel by cell to cell instead  run through the normal conduting system for most part in the circuit)
  • Verapamil sensitive .(Mimic AV nodal Tach)
  • Degeneration into VF is  rare  and hence  SCD is not a big  issue
  • Tachycardic myopathy can occur.

fascicular vt ventricular tachycardia  ecg  svt avnrt avrt wpw

Note:

Fascicular tachycardia is also known in several names.

It forms the bulk of the causes for  idiopathic left ventricular VTs .Other being LVOT VT.

Described first by Cohen in 1974 , followed by Zipes , when they noticed  it was possible to reproduce atrial induction of VT.

Belhassen in 1984 found the verapamil sensitivity of this VT

Other synonyms some times used are

  • Septal VT
  • Narrrow qrs VT

Download high resolution table

Fascicular tachycardia

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