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 .
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 .