Archive for the ‘WPW syndrome’ Category

If some body is struggling with same problem, say for over three decades , there is something seriously wrong with the way we deal with the problem. How do you localise accessory pathway in WPW syndrome from 12 lead ECG ? is one such entity, This question is asked exclusively in cardiology board exams. Now a 2023 paper from EUROPACE claims, it has come out with a simple algorithm bettering all the previous ones. Please check it for yourself.

One thing we can say with conviction is most of these embryological remnant pathways are posteriorly or laterally dragged in peri AV annular region or the para septal region. Very few appear anteriorly, if anterior it is more often placed on the right side.

Why should we take this question easy ?

Try asking any experienced EP specialist* to localise a pathway in given 12 lead ECG . Don’t get surprised by a long silence before they commit, because they know the truth, and how delicate this question might sound on quiet a few occasion, because of various anatomical and physiological reasons.

*Never fail to appreciate their hard long hours in cath lab to spot, analyse and shoot these tracts.(EP stuff is not like angioplasties, which, many can do even in half sleep!)

Final message

Yes, localising WPW can be either a fascinating or frustrating exercise depending on our understanding about the attitudinal cardiac anatomy, variable autonomic tone dependent morphological behaviour of delta waves, PR intervals, QRS axis ,the transition zones etc. Shrewd fellows may go through this 12 lead stress test. ,

For others just try to localise right from left , & then posterior or lateral Forget the anterior ones. This is more than suffice. Unlike drug trials, where statistics are often battered , here the Incident numbers are the key measure of truth. (Even without seeing a ECG you are likely to be correct in 80 % times, if you localise the pathway to posterior, para-septal or left lateral zones. )


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We know , any wide QRS tachycardia  would argue us to make a default diagnosis of VT.But,  one has to be extremely cautious to apply this rule if  wide QRS  tachycardia shows  significant irregularity in RR interval .

All classical VTs are fairly regular tachycardia (Note the  key words , fair and regular) . Small cycle length variations are observed in VT,  but they are usually not discernible in surface ECG.

There are no practical rules .A well  appreciable  irregularity in RR interval will seriously  question the diagnosis of classical VT. To make an another statement, most of the  irregular wide QRS tachycardias infact turns out to be  atrial fibrillation with some form distal widening mechanism .(Preexisting blocks, or rate dependent  or antidromic conduction through accessory  pathways)

However , irregularity  is still possible during VT .(May be less than 10% of times)

When can VT can be irregular ?

  1. Irregularity is observed  immediately at the onset of VT as the re- entrant circuit warms up and tries tosettle down
  2. AV dissociation  can make the VT irregular but it is subtle .(This AV dissociation is absent if retrograde VA conduction is intact)
  3. Multiple reentry circuits with two morphological VTs dissociating themselves
  4. VT with multiple exit points and epicardial breakthroughs
  5. A drugged VT.Amiodarone modified VT can be irregular as it can variably lengthens  the re-entrant  circuits and inducing VA block and precipitating AV dissociation.
  6. Multi- focal VT  (We have MAT in atria do we really have MVT ? (Why not , are we missing it ?)

Final message

Statistically , as well as realistically  , the commonest cause for  any highly irregular tachycardia turns out to be AF , whether  QRS is wide or narrow !

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