Rapid A. Fib or PACs?

zacarias, ASN, RN · Apr 23, 2006

I don't know if this is right. But I think that if you see PACs, then it is likely that the patient's baseline rhythm is probably NSR. Now if it looks like A-fib, it's possible that a person is having numerous PACs that the rhythm looks irregular.

If a person is in real a-fib, you shouldn't ever be able see a PAC.

Dinith88 · Apr 24, 2006

I concur with everyone else who said that it is impossible to have PAC's in a-fib. Heart must be in a sinus rhythm to have pac.

VicChic · Apr 25, 2006

The PAC's are no longer a part of the A-fib rhythm. Of course the PAC's are true contractions and no longer a fibrillation. However, occassional or even frequent PAC's do occur with A-fib b/c they are ECTOPIC beats, electrical impulses originating from a different foci, but what it indicates is the heart's attempt to convert back to sinus. It's just taking baby steps first. Gotta crawl before you walk. It's totally normal to see when you're trying to pharmaceutically cardiovert.

telehead · Apr 25, 2006

The PAC's are no longer a part of the A-fib rhythm. Of course the PAC's are true contractions and no longer a fibrillation. However, occassional or even frequent PAC's do occur with A-fib b/c they are ECTOPIC beats, electrical impulses originating from a different foci, but what it indicates is the heart's attempt to convert back to sinus. It's just taking baby steps first. Gotta crawl before you walk. It's totally normal to see when you're trying to pharmaceutically cardiovert.

I still disagree with your explanation. First, the ectopic beats are not typically indications of the heart's attempt to convert- just the opposite. The ectopic beats are indicative of considerable irritation in the atrial cardiac tissue. In actuality, it's typically a pause (a single pause or multiple 1-2 second pauses) that is seen just prior to a conversion back to sinus, not a crawl/walk series of pac's. Sort of the body's own adenosine treatment, but on a much smaller scale.

Secondly, the very nature of afib, the 'quivering' of the atria, is due exactly to the many ectopic impulse origination points that you describe. As such, these multi-focal ectopic beats define afib rather than account for pac's within an afib rhythm.

Interesting topic of discussion.

harley_fan · Apr 25, 2006

I thought there would be a clear cut answer!!! My thought process was along the lines of telehead but I always like to see how other people explain things. So, thanks for all the input!

PICC ACE · Apr 26, 2006

PAC's in AFib? Simple answer,no. What are the characteristics of PAC's? Conduction originates in SA node,usually have a measurable PR if the P isn't buried in the T,and occurs earlier than the next anticipated sinus beat. In fib,you have no regular SA activity,no measurable PR's,and no regular sinus beats. What were the beats like that others were calling PAC's? One thing you can see in AFib is an aberrantly-conducted atrially-generated beat that some might call a PAC. In lead II,the QRS would look obviously different from the usual ones but not be as wide or have a big downward deflection like a PVC.

Dinith88 · Apr 26, 2006

The PAC's are no longer a part of the A-fib rhythm. Of course the PAC's are true contractions and no longer a fibrillation. However, occassional or even frequent PAC's do occur with A-fib b/c they are ECTOPIC beats, electrical impulses originating from a different foci, but what it indicates is the heart's attempt to convert back to sinus. It's just taking baby steps first. Gotta crawl before you walk. It's totally normal to see when you're trying to pharmaceutically cardiovert.

I understand where you're coming from, but its a little inacurate(like my spelling).

In order for a p-wave (atrial contraction) to occur, the atrial myocardial cells have to be 'loaded' or all re-polarized at the same time before they can 'fire' in an organized (p-wave/contraction) manner. When you see someone convert from a-fib to sinus, there's always an 'asystolic pause'...it can be very small, or extended (4 second pause that freaks the unit out). This happens in chemical cardioversion and is the entire reason why electrical cardioversion works/converts them.

IN atrail fib, there is all that chaotic-fibrillashaking-stuff going on...which prohibits oranized waves/contractions...so p-waves dont/cant superimpose themselves on atrial-fibrillation strips(which is what i think you mean by 'ectopic' atrial beats seen in a-fib.)

VicChic · Apr 26, 2006

PAC's in Afib? Of course not. PAC's with Afib. Yes, as was stated earlier by myself and a few others, you can have Afib with runs of PAC's or just frequent PAC's. There's is a difference b/c in Afib=no p wave=obviously not an atrial contraction of any sort. PAC's with Afib=a p wave occured from somewhere= there's atrial electrical impulses from somewhere trying to be recognized once again. So yes the underlying rhythm may be Afib, but once you see a p wave present (and it's probably best to be in lead II for this particular rhythm interpretation) you no longer can call this Afib. It has to be Atrial Contraction and obviously premature since the underlying rhythm is still irregular. Where I've worked this is seen all too often. Remember, afib doesn't always necessarily mean the atria are incapable of emitting electrical activity; the only thing that is definite is the interruption of a normal conduction of the heart's electrical activity, which should originate from the SA node but doesn't. Sometimes with a chronic Afib'er, you put them on Amiodorone, Cardizem, or some other antiarrhythmic and/or Digoxin, and then you see more PAC's then ever b/c you've now broken up that incorrect pathway of electrical impulses that heart was using and rate control has now allowed SA node to get back to being the impulse generator again. Seen all the time in nuc med with stress test, and in CCU, and often seen by paramedics in the field if a person has just been in a lot of trauma.

Dinith88 · Apr 27, 2006

PAC's in Afib? Of course not. PAC's with Afib. Yes, as was stated earlier by myself and a few others, you can have Afib with runs of PAC's or just frequent PAC's. There's is a difference b/c in Afib=no p wave=obviously not an atrial contraction of any sort. PAC's with Afib=a p wave occured from somewhere= there's atrial electrical impulses from somewhere trying to be recognized once again. So yes the underlying rhythm may be Afib, but once you see a p wave present (and it's probably best to be in lead II for this particular rhythm interpretation) you no longer can call this Afib. It has to be Atrial Contraction and obviously premature since the underlying rhythm is still irregular. Where I've worked this is seen all too often. Remember, afib doesn't always necessarily mean the atria are incapable of emitting electrical activity; the only thing that is definite is the interruption of a normal conduction of the heart's electrical activity, which should originate from the SA node but doesn't. Sometimes with a chronic Afib'er, you put them on Amiodorone, Cardizem, or some other antiarrhythmic and/or Digoxin, and then you see more PAC's then ever b/c you've now broken up that incorrect pathway of electrical impulses that heart was using and rate control has now allowed SA node to get back to being the impulse generator again. Seen all the time in nuc med with stress test, and in CCU, and often seen by paramedics in the field if a person has just been in a lot of trauma.

VicChic, you're stretching. Next time you're at work ask a cardiologist.

VicChic · Apr 28, 2006

Not stretching, just explaining what I, along with others in cardiac nursing/cardiology already know and accept to be fact. Sorry you don't comprehend but you are in good company. After all, it's a cardiologist that had to explain it to me FYI. :wink2: I had to learn it myself and now I'm sharing it with someone else, because they were smart enough to ask and then smart enough to listen. You're right, you should ask a experienced cardiologist.... so they can turn around and tell you the same thing. Have a blessed day!

I just want to applaud the OP for using their resources to investigate such a thought-provoking question that obviously showed good critical thinking b/c they thought deeper than just "textbook" explanations. Once again, that's a beautiful skill in nursing that Harley Fan has obviously mastered. It's the funky stuff that keeps it interesting so keep on keeping on! Embrace it and have fun with it. Keep an open mind so your mind can absorb information that's new to you, and most of all keep that teachable attitude. You can't lose with that! Buh-Bye!

telehead · Apr 28, 2006

Not stretching, just explaining what I, along with others in cardiac nursing/cardiology already know and accept to be fact. Sorry you don't comprehend but you are in good company. After all, it's a cardiologist that had to explain it to me FYI. :wink2: I had to learn it myself and now I'm sharing it with someone else, because they were smart enough to ask and then smart enough to listen. You're right, you should ask a experienced cardiologist.... so they can turn around and tell you the same thing. Have a blessed day!

I'm torn between responding or allowing this dead horse to lie... But discussion is fun. :)

With all due respect, I believe you have either interpreted what your cardiologist said incorrectly or taken the question to him/her in a vague manner. It was your previous response that leads me to believe this:

PAC's in Afib? Of course not. PAC's with Afib. Yes, as was stated earlier by myself and a few others, you can have Afib with runs of PAC's or just frequent PAC's. There's is a difference b/c in Afib=no p wave=obviously not an atrial contraction of any sort. PAC's with Afib=a p wave occured from somewhere= there's atrial electrical impulses from somewhere trying to be recognized once again. So yes the underlying rhythm may be Afib, but once you see a p wave present (and it's probably best to be in lead II for this particular rhythm interpretation) you no longer can call this Afib. It has to be Atrial Contraction and obviously premature since the underlying rhythm is still irregular.

This is, I believe, tho I don't want to speak for Dinith88, the stretch Dinith88 was referring to earlier and where I believe your argument falls into vague/lack of comprehension mode (lack of comprehension by me may also be the answer). "It depends on what the definition of 'is' is."

I contend your use of with and in is simply semantics which raise a straw man in the discussion. By stating a difference between with and in as you've done, you've actually created two different rhythms. Your statement that "in Afib=no p wave=obviously not an atrial contraction of any sort." is precisely what many of us have been saying all along and it is the answer to the question originally posed. The strawman appears when you tried to change that to with afib. You present a definition that places the presence of p-waves as part of afib when it's actually only possible once the rhythm changes from afib to anything else, as I believe you (inadvertantly?) state here: So yes the underlying rhythm may be Afib, but once you see a p wave present (and it's probably best to be in lead II for this particular rhythm interpretation) you no longer can call this Afib. It has to be Atrial Contraction and obviously premature since the underlying rhythm is still irregular.

The bold section, I agree with but I am unable to reconcile your statements in the first part- "may be afib" with the second part- "no longer can call this afib".

The last part, I don't agree with either. If the underlying rhythm is still irregular, but p-waves are still present, then you don't have afib, under/over/between or otherwise-lying. If it's irregular, then you have sinus arrhythmia or you have sinus with frequent pac's.

It comes down to this- a p wave on a strip indicates depolarization of the atria. The "quivering" of the atria occurs because there are multiple points in the atria (irritability) firing randomly, thus preventing the atria from fully depolarizing (or repolarizing). The atria hang, electrically, in the threshold region. The AV node, with its much slower calcium channel conduction system, allows much fewer atrial impulses through than are created. This is why you see irregularity. The first impulse that gets through might come from point A but the second one may come from point B or point C. Now when you consider the irritable atria may have 100 (randomly chosen number) points of electrical impulse origin, you can see why the resulting rhythm is irregular. What you don't ever have during this time is a fully depolarized atria and thus no full atrial contraction, therefor, you don't ever have a mature or premature atrial contraction during afib.

That's my story and I'm sticking to it.... unless someone can change my mind.

allnurses Guide · Apr 28, 2006

See? (Refer to my earlier post about the ever-changing interpretations of heart rhythms). :uhoh3:

Y'all keep talking though - I'm learning, just not sure what. :monkeydance:

steph