Atrial fibrilation with normal S1 and S2 sounds?

nurseprnRN, BSN, RN · Mar 5, 2013

If you remember what the S1 and S2 are, you will see that they have nothing to do c atrial action. Think about that.

julienurse2b · Mar 5, 2013

afib- cardiac dysrhythmia, rapid, irregular heart beat. S1 S2 are the normal first and second heart sounds.

I havent learned much about cardiac rhythms yet, but I was just confused because the nurse before me had charted that the patient had afib, but left the spot empty for s1 and s2 sounds.

Double-Helix, BSN, RN · Mar 5, 2013

S1 is made by the tricuspid and mitral values closing. S2 is made by the pulmonary and aortic valves closing. A murmur is abnormal turbulent blood flow through a narrowed space or back flow through a valve. The atria regulate none of these, so yes, it is possible to have a-fib and normal heart sounds.

nurseprnRN, BSN, RN · Mar 6, 2013

afib- cardiac dysrhythmia, rapid, irregular heart beat. S1 S2 are the normal first and second heart sounds.
I havent learned much about cardiac rhythms yet, but I was just confused because the nurse before me had charted that the patient had afib, but left the spot empty for s1 and s2 sounds.

I am guessing that's because she doesn't know what they are either. :) Ashley kindly gave you the answer.

During systole (ventricular contraction) the mitral and tricuspid valves slam shut to keep blood from moving backward up into the atria. The sound of that happening is S1. A murmur heard over the mitral area during S1 indicates that the valve isn't closing all the way and some blood is sloshing backwards. And aha! A murmur heard over the aortic valve area during systole tells you that the AV isn't opening wide (it's stuck/stenosed) so there's a lot of racket as the blood tries to get out through it.

Then during diastole, the aortic and pulmonic valves slam shut to keep the blood from going backwards into the ventricles. The sound of that happening is the S2. A murmur over the AV during S2 indicates that the valve isn't closing all the way and some blood is sloshing backwards. Likewise, a mitral murmur during diastole, when the ventricle is supposed to be filling from the atrium, says the mitral valve isn't opening up wide the way it should, making more racket as the blood tries to get past it.

I strongly, strongly suggest that you follow the path of the blood through the heart so you can see the relationships between the chambers and the valves. Vena cava > right atrium > tricuspid valve> right ventricle > pulmonic valve > pulmonary artery > LUNGS > pulmonary vein > left atrium > mitral valve > left ventricle > aortic valve > aorta

This tutorial came from the following question:

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You'll be able to hear heart sounds best DOWNSTREAM of where they occur... so listen to aortic sounds best just north of the AV, in the aorta. Mitral sounds are best heard near the apex of the heart.

Do you have a clear idea of which sounds correspond to which actions? (we're not gonna worry about tricuspid and pulmonic sounds today, just the leftsided valves 'cus they are in the high-pressure circuit and so they make the most noise. They are also the ones that get injured or messed up the most, by far.)

S1 is the sound made when the ventricles are full at the end of diastole and just starting to contract in systole, and the sound you hear is the mitral valve slammin' shut to prevent backwards flow when the pressure goes up in the ventricle. You hear this best at the apex of the heart, down sorta where the bottom of the left bra cup hits the ribs.

S2 is the sound the aortic valve makes when it slams shut at the end of systole & the beginning of diastole, to prevent blood from backflow out of the aorta into the ventricle from when it just came. You hear this best at the arch.

Lub (S1, mitral valve closes)-Dub (S2, aortic valve closes). You can tell which is which by where you hear them best. Go back and forth between the two places a couple of times and you'll see what I mean.

OK. Now you need to get a feel for the difference for murmurs in systole and diastole, and why they tell you what they tell you.

There are two ways you can mess up a valve. You can make it too tight (stenosis) so there's a lot of resistance to flow (think how a running garden hose feels-- and sounds!-- when you squeeze it). Or you can have it too loose (regurgitation, incompetence) so it doesn't do its job of preventing backflow. Both of these things make funny noises, sorta blurry sounds, rather than that nice "close the door" sound we call normal. Just to make life interesting, you can also have a stenosis and a regurg in the same valve, like when it gets all calcified and scarred and stuck partway open, so it doesn't pass blood thru easily but it also doesn't do a good job of preventing backflow.

If you think about what's going on at each valve in systole and diastole AND you remember to listen in the right place for each valve, you can figure out whether you have a systolic or diastolic murmur and which valve it's coming from.

Draw a picture of the 4 chambers of the heart. Include the mitral valve between the a & v on the left side, and the aortic valve at the outflow to the ventricle into the aorta.

What goes on at the mitral valve? In diastole, it's wide open, so blood can go from the atrium to the ventricle (a quiet thing). In systole, it slams shut (the S1). You hear the mitral valve best at.... the apex, right. SO... if you have a mitral stenosis, things'll be noisiest there in diastole, because the blood will be trying to go thru a too-small hole into the ventricle. If you have a mitral regurgitation, there’ll be a blurry noise there at systole. Think about this and don't go on until it is clear to you.

What goes on at the aortic valve? In systole, it's open so blood can get out to the aorta (quiet). In diastole it's slammin' the door, so blood can't go backwards (that’s the S2). So if you have a stenosis there, when and where do you hear the blurry noise? Right, in systole, and just downstream of the valve in the arch, as the ventricle tries to force blood thru a tight (stenotic) opening. OK, so if you have a regurgitation there, when do you hear it? Bingo, in diastole, because the partly-ajar valve is unable to slam shut and blood comes backwards thru it, making a racket.

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You wouldn't hear that much in the way of aortic valve sounds so far away from the aorta, and you wouldn't hear mitral valve sounds there at all. You're thinking of the bruit made by blood banging around in an aortic aneurysm.

Does this make sense?

allnurses Guide · Mar 6, 2013

Was she IIR?

Was she actively paced?

Remember that many people have paroxysmal afib and spend most of their time in NSR and transition in and out of afib.

You can hear variations in S1 in active afib but you may not.

nurseprnRN, BSN, RN · Mar 7, 2013

The variations have to do with the preload that varies with afib, if the OP is wondering, but they will still occur because they are created by ventricular action. No ventricular action, no S1 (and no more worrying about that patient-- he's dead or on a ventricular device :) )