A Fib With Aberrancy

[martymoose, BSN, RN]

I've noticed a lot more a fibs looking like runs of VT, but am told they are "most likely afib with aberrancy" how do you know that they are not VT. The rate ends up being in the 150's or more ( so RVR). I guess maybe the QRS is a tad bit narrower to not be VT ? They are not usually sustained, but can be frequent.

[0.9%NormalSarah, BSN, RN]

Yeah I think it would just be a difference in how lengthened the QRS complex is. Wide QRS, V-tach, narrow it’s a supraventricular tachycardia. Now whether that is a-fib, even a-flutter or SVT, that depends. Also they are only having runs? It seems to me you more typically see runs of v-tach rather than being in and out of a-fib so frequently. 

[MunoRN, RN]

Aberrant beats occur in A-fib or other tachyarrhythmias because the right bundle branch typically takes slightly longer to repolarize than the left.  When the rate is fast enough, or in the case of A-fib when the next impulse to making it through the SA node is timed just right so that the left bundle branch has repolarized but the right bundle branch is not then you get a QRS which appears as a RBBB.  

I would say the main indicator of RVR with aberrancy is irregular while a ventricular tachycardia is regular.  Identifying a RBBB would further help differentiate the two.  Although really it's sort of academic, the bigger question is whether or not it's resulting in effective cardiac output and perfusion.