Dr.S.Venkatesan MD

Irregular  wide qrs tachycardia is a fairly common clinical entity in any cardiac emergency room. The moment you ask about  such tachycardia ,  9/10  fellows will  come out with a  prompt answer   ” AF with WPW syndrome” even before you complete the question !  It is not that common  as we perceive .The problem is with  our traditional teaching methods and the attraction of human brains to  rare and exotic disorders.

traditionally   SVT with aberrancy  is   diagnosed  mainly  in the setting of regular tachycardia .

We often  forget  “AF with aberrancy”  is equally common  , and  it presents   with a  irregular  wide qrs tachycardia . 

I  wonder whether  this phenomenon  can be termed as  orthodromic aberrancy .This can directly compete  in the differential diagnosis  of  antidromic AF  with  WPW !

It should also be mentioned antidromic  AF can run into very high rates  as accessory pathways do not check the incoming signals while orthodromic aberrancy the ventricular rates can not exceed 220 or so at least theoretically . (This simple clue can clinch the issue in favor of  WPW )

There is no proper  published data available for the true  incidence of AF with orthodromic aberrancy in general population

In fact , there are  many  electrical  environments for AF  to  become a  wide qrs AF

1. AF  with  Antidromic conduction through accessory WPW pathway.

2. AF with Orthodromic aberrancy ( Non WPW – Similar to  any SVT with aberrancy )

3. AF with pre existing LBBB

4. AF  with Amiodarone effect. (Especially with DCM and cumulative load of Amiodarone )

5. AF with electrolytic /  especially excess  intra-cellualr  potassium

6. Finally , even  Atrial based pacing (DDD)  can cause wide qrs irregular tachycardia when  mode switching  fails .Here the  ventricles  may track the  atrial irregularity  and respond with a  wide qrs  bizarre tachycardia .

Final message

There are many causes for  wide qrs tachycardias  in  Atrial fibrillation . WPW with anti-dromic conduction is just  one of them .We need to approach the issue with an open mind .Please  be reminded , once contemplated  WPW syndrome  can be a powerful thought blocker  !

Note : *We are not including   polymorphic ventricular tachycardia here .It is an  important subset of  wide qrs irregular  tachycardia.

** VT can co-exist with AF .This is not   surprising  as  many of the diffuse cardiomyopathies  involve  both atria and ventricle  with extensive scarring and fibrosis  a perfect trigger for  both atrial and ventricular arrhythmias .