In today's video we are talking about extract heart sounds: S3 and S4, in
particular we're going to start with a quick review of S1 and S2 and maybe get a
little saucy today as I am going to give you a real fun mnemonic - I think it's fun to help
you remember how S3 and S4 are different. We're going to take care of that right
after this. Welcome back my name is Tammy and this is NurseMinder and on this
channel we do everything nursing so if you're new here consider subscribing
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So let's first get started with a quick review of what S1 and S2 sound like and
where they're originating. S1 is our lub, S2 is our dub. So S1 involves the
tricuspid and mitral or bicuspid as it is known. Those valves are closing
causing a snap and that's our S1 sound. This coincides with systole and
coincides with that pulse. So you can find S1 by palpating a pulse and auscultating.
S2 is the dub. It is when our pulmonic and aortic valves close after - and
it's the onset of diastole, sorry, not after. it is the onset of diastole. What I
didn't talk about in our first video is the chordae tendinae. So I've drawn
those in today because the chordae tendinae have a role to play in those extra
heart sounds and we'll get into that shortly. But essentially what those are
the fibrinous cartilage - fibrous cartilage that holds onto those flaps of
the valve to prevent them from hyper extending if you would, so as the flap
opens the chordae tendinae would relax and then when they close their
tense and they're at their longest so it kind of prevents them from going too
far back and into the atria themselves.We willl begin our discussion looking at the flow
of blood as those valves are opening and closing. So we're actually going to start
with S1. We have our AV valves closed, so that's our mitral and tricuspid ,and
are semilunar is open. So you'll see here that the blood is going from
the ventricles, we have contraction of the ventricles, and what is being ejected
through the semilunar valves so it can go out to the pulmonary system for
oxygenation or to the body to deliver nutrients. AV closes, there's our lub
SL is open. When we are finished with the blood ejecting from the ventricles,
both the SL and the AV node will be closed for a very brief time but the
sound we're hearing at S2 is in fact the semilunar valves closing - thats the aortic
and pulmonic .During the isometric relaxation phase, because there's no
valves for the superior vena cava to drain into the right atrium and there's
no valves preventing blood coming through the pulmonary artery into the
left atrium, blood just naturally will flow into there.
Now as the pressure increases, that will force our AV valves to open and blood
will be ejected as there's an active contraction happening here at the same
time, into the ventricles. That eventually slows as the atria start to empty its
contents and the ventricles fill up - then we start to get a slow diastole,
so the semilunar valves are still closed, AV valve is still opened. As those
ventricles start to fill up, the flow will start to slow down and there's
actually a physiological, normal physiological thing that happens here,
and it's called atrial kick,
and that's kind of like when those atria contract and then they just get one more oomph
so that the last little bit of blood can be squeezed out of the atria,
into the ventricles, maximizing that ventricular contraction so we get the
most blood ejected out into the body. Now interesting enough, both of our extra
heart sounds, S3 and S4 occur during diastole. We're going to talk about S3
first. In ventricular gallop what we're hearing is a tensing of that chordae
tendineae and there's a few reasons - we might have that fluid overload,
congestive heart failure, my ventricle is an ineffective pump and I'm not completely
evacuating all that blood with ejection - so I have a larger pool of blood sitting
here. In addition I've got a whole lot of blood coming in and it's not able to
take it all - so these chordae tendineae are tensing up and they're causing kind
of a tap, a third sound. So that's my chordae tendinae.
Now to give you a mnemonic to help you remember this, there's a few out there.
You may have heard of Tennessee. Ten-ne- ssee, Tennessee, Tennessee, But that
kind of confuses people sometimes. This one's a little bit easier - Fuck, you're
screwed, fucked - you're screwed, fuck - you're screwed. Another way to remember
this is lub dub ta, lub dub ta, lub dub ta, fuck -you're screwed, fuck - your
screwed, lub dub ta, lub dub ta. In S4, also known as the atrial gallop
the AV values are still open. As I said these are both in diastole,
which means filling. So when we look at the ventricles for an S4 you see that
they're resistant - they're really not wanting to stretch and accept. So they have
a limited amount of volume of blood that we can take in there. This is common with
hypertension and hypertrophy, but the atria still have all of this blood to
deliver and so it's going to get a little bit more forceful and it's going to
insist that's heart take more blood than it's capable of taking. And so what
we end up having is this extra atrial kick almost like it kicking harder. So we
get this S4 happening just before those AV values close. Now the way to remember
this one is, well fuck - you, well fuck - you.
In this case the non-compliant ventricles are what's causing the
vibration and causing that S4 heart sound. When we come back to the heart we can
see - let's just get rid of our S3 and S4 for a minute;
lub dub, lub dub, lub dub. AV valves closing talking the lub sound, semilunar valves
opening allowing blood to eject. Semilunar valves and AV valves are
closed here at the same time but the sound we're hearing is the seminlunar
valves closing. dub
Now the S4 and the S3 - sorry the S3 is here. With the S3 I got a heart that's
too full of fluid, it doesn't want to take very much, the chordae tendineae are
kind of startled and it tenses up - my S3 and so then we get, fuck - you're
screwed, fuck - you're screwed.
I will put S4 in orange here just to differentiate that. S4, well fuck you
So when you're listening to those heart sounds remember lub dub, lub dub, lub dub
lub dub ta, lub dub, ta lub dub ta - le lub dub, le lub dub, le lub dub. and if that
doesn't help you you can always rely on the old standby, fuck - you're screwed or
well fuck - you. So when your auscultate next time and the hearts telling you to
fuck your screwed or the heart saying well fuck you, you know you've got
yourself an S3 or an S4. The best place to listen for these is over the mitral
valve so that is that midclavicular fifth intercostal space and if you have
your patient roll onto the left side, you will have an even a better chance of
catching that. And don't forget for murmurs and extra heart sounds we want to use
our stethoscope lightly. If you press too hard you can actually include that extra
heart sound and you couldn miss it all together - and who wants to miss the heart
telling you off - not me. Don't forget to subscribe, just hit that subscribe button
below and you'll get the next video when it's released. Until next time, get that
stethoscope out, practice your auscultation, and make it a
great day :)