Now let us talk about respiration and our
focus here is going to be upon our S2. So
before we begin, you tell me about S2
again. S2 is a diastolic event, is it not?
Yes. What happens during diastole? You have
closure of the aortic followed by the pulmonic.
We had A2, P2. Larup, darup, larup.
Larup is S1, let us leave that alone. Let us
focus on S2. Now if you’ve understood everything
that I have said up until now, when I talk to
you about the splitting of your S2 physiologically,
then this will make sense doing inspiration.
Now work with me here. Ready. Deep breath,
diaphragm contracts moves down. What happens
to your venous return? Tell me. Increased.
Good. So you have increased your venous return
to the right side upon inspiration. Where
is there more blood? Well there are two doors.
One is over there and one is over there. And
even 1000 people running through that door
and you have two people running through that
door, which door is going to close first?
Obviously the one with two people. If
you tell me, 1000 people, I can’t help you.
I really can’t. So here we go. Inspiration
is more amount of blood on the right side.
That is your 1000 people. That is going to
take a long time for that door to close. What
is that door with the 1000 people right now?
That's your P2. So your second heart sound,
your pulmonic valve closing upon inspiration
is going to be much more delayed than your
aortic. What do we call this? A physiologic
split. Take a look at the inspiration, please.
You see that widening of A2, P2. Doesn't that
widening the space between A2, P2 look longer
in length than upon expiration. Upon expiration,
what happens to your diaphragm? Diaghragm
comes up, thoracic pressure increases and
so, therefore, your venous return is not as
much on the right side. And so therefore what
will happen to distance between A2, P2? It
is decreased a little bit. Now, is this pathologic?
No. It is called a physiologic split.
This is occurring in you and me right now.
When we inspire expire, we have changes in
the span and length of A2, P2. Hope that is
That's the physiologic split. Let's continue, now we have something
called a persistent or, more importantly,
a widened split. Right off the bat, I wish
to tell you, do not confuse your widened split
with the fixed split. "Dr. Raj, it sounds
like the same darn thing." Granted perhaps.
But medically and clinically not at all. Two
distinct diagnoses that must be understood
right off the bat. Widened is not the same thing
as fixed. What does widened mean? Well,
let us say that your patient has something
like right bundle branch block. What does
a block mean to you? Well, the reason I
ask you that is because, I am not stating the obvious.
A block does not mean that no impulses are
passing through. You have heard of AV block,
you have heard of first-degree, second-degree
AV block? Have you not? And what happens in
those blocks? There is delayed conduction
of the impulses. Correct? So in right bundle branch
block, you will have a delayed conduction
through the right bundle. Is that clear? When
you have a delayed conduction through the
right bundle, then what happens to your P2?
It closes a little bit later, but it is not
fixed. It is not fixed. I want you to take
a look at normal and you take a look at your
second heart sound. Expiration, inspiration.
When do you have that widening? Only during inspiration and
that is called a physiologic split. That is
what normal is. A physiologic split. I want
you to compare that to the wideened or the
persistent, not the same thing as fixed. Right
bundle branch block. When should you have
more widening? During inspiration. Take a look
at inspiration here under persistent, do you
see that? Good. And do you have widening? Sure you do,
but it is a lot wider than what it was with
inspiration or normally. Take a look at expiration.
Expiration, the widening is a little bit lessened,
but it is still longer than what was found
in normal. Is that clear? You still have variation like an accordion,
back and forward, you still have that inspiration,
expiration, widening and closing of the lengthened
span, but this is called persistent. Our diagnosis
and differentials include right bundle branch
block and pulmonic stenosis. Why isn't left
bundle branch block here? You see that why isn't
LBBB here? Because the left bundle branch
block would mean what? Close your eyes. It
means I can't have proper conduction to the
left bundle branch. So where is my depolarization
passing through? Through the right bundle
branch. So which valve is going to close first?
Pulmonic, then your aortic. Is that clear?
It has nothing to do with persistent split.
That is called a paradoxical split, isn't it?
So a left bundle branch block is
going to give you a parodoxical split. Is
that simple. In right bundle branch, it was
going to give you something like your persistent
or a widened split. Then we come to our fixed.
Are we clear here? It is important that you
pay attention to terminology. I want you to take
a look at normal. We have gone through that
plenty, just leave that alone. You know about
the physiologic split.
Now let us take a look at ASD. With atrial
septal defect, this is my issue. It is the
fact all of the time let us say that the most
common genetically is ostium secundum. With
an ostium secundum, say that the foraminal
valves remain open and you would then create
an atrial septal defect. What kind of shunt
A left to right shunt. So you are not going
to have cyanosis, are you? No, because it's a left to
right shunt. You can still have oxygenation
to the tissue. That is not going to be an
issue. But now with that blood, which is constantly
moving, where are we moving from? Left atrium to right
atrium, constantly. With the constant amount of blood
going into the right atrium tell me about
the pulmonic valve. It is always going to
be fixed. It is always going to be widened. I want you
to take a look at expiration, inspiration
under fixed, our prime and main differential
would be atrial septal defect in which there
is not going to be any widening or physiologic
split of A2, P2. We call this fixed. Number 1 differential,
atrial septal defect. We will go one step
further because any board exam clinically
what have you, will want you to know or
require you to know where on your chest you
would hear the atrial septal defect murmur.
But it first begins with your understanding
of a fixed split. Now we have a paradoxical
split. Now we can walk through this quickly.
We have left bundle branch block. Take a look
at normal please. A2, P2, expiration, inspiration.
Take a look at paradoxical. What does paradoxical mean? Opposite.
When was the last time you have heard of paradoxical?
What is another common theme of paradoxial
come into play? How about a paradoxial embolus?
Remember DVT. A DVT would be a thrombus and
if it embolizes, you end up in a pulmonary
embolism. That is not paradoxical. But if
you have something like a septal defect, then
you might have a DVT, which will then embolize
the opposite side and you call that what? A
paradoxical embolus. Here we have a paradoxical
split. Is that clear? So what is happening?
There is no proper depolarization of the left
bundle branch. So where is my conduction passing
through? The right bundle branch. First P2,
then A2. That is not normal. That is paradoxical
split. What is another one? With an aortic
stenosis, and we will get into this in a little
bit. But it is a systolic murmur. The aortic
valve does not want to open. And if it doesn't
want to open, you are sure that it doesn’t
want to close, so, therefore, you might have
a paradoxical split. It is important that
you understand the difference between number 1 physiologic
split of S2. A widened split of S2. Differential
right bundle branch block. Number 3, fixed split.
Number 1 diagnosis, atrial septal defect. Are we good? Paradoxical