A fib RVR vs SVT

[NurseKnope, BSN, MSN, RN]

Sorry if this has been asked a lot, I’ve tried searching but couldn’t find anything.

I’m having a hard time differentiating between a fib with rvr and svt. Is a fib always considered rvr if the rate is greater than 100? Does it become svt if the rate is greater than 150?
I may be splitting hairs. I understand causes and treatments but just don’t know these nuances.

If anyone has any resources that would be appreciated. Dr Google has not been helpful and none of my textbooks/ekg books go into this much detail.

[MunoRN, RN]

The term "SVT" is often used to refer to a re-entry SVT, but really the term SVT refers to any rhythm with a ventricular rate of greater than 100 bpm that originates above the ventricles, which can be identified on an EKG as a narrow QRS, with the exception of a rhythm that originates above the ventricles but with a  BBB present.  SVT includes sinus tach, A-fib or atrial flutter with a ventricular rate over 100 bpm, etc.  

A re-entry SVT is where each ventricular contraction triggers an electrical impulse that travels back up to the junction or the atria and triggers another beat, the heart rate is then determined by the amount of time it takes for the electrical impulses to travel through the continuous loop, which typically results in a rate of around 150 or greater.

Basically, "SVT" is a catch-all term for fast rhythms that appear to originate above the ventricles but that can't be narrowed down any more specifically than that, but often someone using the term is actually referring to a re-entry SVT.

[murseman24, MSN, CRNA]

On 8/26/2020 at 5:38 PM, NurseKnope said:

I’m having a hard time differentiating between a fib with RVR and SVT. Is a fib always considered RVR if the rate is greater than 100? Does it become SVT if the rate is greater than 150?
I may be splitting hairs. I understand causes and treatments but just don’t know these nuances.

If anyone has any resources that would be appreciated. Dr Google has not been helpful and none of my textbooks/ekg books go into this much detail.

Main thing is don't give adenosine to anyone in a-fib, if there is an accessory pathway their ventricular rate may INCREASE and convert to v-fib.  a-fib RVR can be treated with calcium channel blockers and beta blockers.  Quickest distinguishing feature is the regularity of the rhythm, are the QRS complexes spaced evenly apart between each beat? 

[murseman24, MSN, CRNA]

If you're looking for a very easy to read first ekg book, Dubin's "Rapid Interpretaion of EKG's" will get you started.  It's a very easy read with pictures on each page and usually less than a paragraph per page.  It does a fantastic job of explaining basic concepts for ekg interpretation though.

[SweetBabyJames]

Afib w RVR is just fast afib. It’s irregular. SVT is super fast tachycardia, and it’s regular. Basically.

[OUxPhys, BSN, RN]

Actually, SVT stands for Supraventricular Tachycardia. So it occurs above the ventricles in the atria or AV node. So it's a term that covers multiple possibilities. Technically a-fib is a form of SVT, as is atrial tachycardia and AVNRT (atrioventricular nodal reentry tachycardia). The RVR part is A-fib over 120 (I think). 

[CKPM2RN, ASN, EMT-P]

This is a handy little refresher: http://hqmeded-ecg.blogspot.com/2017/08/what-happens-when-you-give-adenosine-to.html

 

[MunoRN, RN]

On 8/28/2020 at 6:56 AM, SweetBabyJames said:

Afib w RVR is just fast afib. It’s irregular. SVT is super fast tachycardia, and it’s regular. Basically.

Sort of, SVT can be irregular or regular as it is a broad description that applies to wide range of rhythms.  A re-entry SVT is regular and typically "super fast" since it's rate is based on the time it takes for electric impulse to travel back up to the atria and then bounce back to the ventricles.

[NurseKnope, BSN, MSN, RN]

Thanks for the responses, you guys. It was really helpful!