00:01
Hi,
welcome to this video in our
series on the electrocardiogram.
00:06
In this one,
we're going to learn about
atrial dysrhythmias and
specifically atrial fibrillation.
00:12
So we're always going
to start with normal.
00:15
So why is this ECG
normal sinus rhythm?
See if you can review in
your mind the criteria
that caused this strip to be
identified as normal sinus rhythm.
00:27
Now compare it
to this rhythm.
00:30
This ECG is atrial
fibrillation,
see the difference?
Where are the P waves?
Where is the regularity
between the QRS complexes?
Okay, this one looks very
different than normal sinus rhythm.
00:47
Remember those patients that we
were not quite sure how to tackle?
Well, now we're finally ready
to try to diagnose them.
00:55
This time around, we're going to
check on this fella right here.
00:59
Since we've already analyzed and
identified a normal sinus rhythm,
you know, at first glance,
then this ain't it.
01:07
There's definitely something
wrong with this ECG.
01:10
But what exactly is it?
Now let's take a closer look.
01:14
Once again, let's recap.
01:16
The electrical impulse travels
from the atria to the ventricles.
01:20
Now its pathway is being
reflected on the ECG paper.
01:24
The impulse originates at
the SA or sinoatrial node,
and it travels
through the atria.
01:30
And this is what causes the atrial
depolarization or contraction
and makes the P wave
on the ECG strip.
01:37
Now at the AV node,
the impulse is still laid
and it's reflected
in the ECG strip
as an isoelectric line
called the PR segment.
01:47
Then the impulse courses
through the Purkinje fibers,
it's causing depolarization or
contraction of the ventricles,
which is reflected on the
paper as the QRS complex.
01:58
Next, the interval of time
between depolarization
and repolarization
of the ventricles
is reflected as a flat,
or isoelectric line called the ST segment.
02:10
And finally,
the ventricle repolarize or relax.
02:15
This is what
forms the T wave.
02:17
Take a look at the graphic
we have for you here.
02:20
Start up at the top,
I'd love for you to put your finger
at the top there at the SA node.
02:26
Now look at that signal
shooting out across both atria.
02:30
Then you see it
hit the AV node,
and it's disseminated
into the ventricles.
02:36
Now the atrium
are contracting,
you have a little
bit of a pause,
remember, that's the PR,
and then the
ventricles contract.
02:43
So I would encourage you
to spend some time with us.
02:47
Look how organized it
is, how systematic it is,
how the heart is pumping atrium,
ventricles, atrium, ventricles,
atrium ventricles.
02:56
That's what makes
an efficient pump.
03:00
Now we're gonna compare
it to atrial fibrillation.
03:03
You see we have
going on there?
It's like chaos, right?
So the atrium are not firing
as systematically as you see
SA node to AV node
down to the ventricles.
03:17
So not even all of the
signals are making it through.
03:22
That's what atrial fibrillation
looks like in the heart.
03:26
So I really would encourage you
if you have solid in your mind,
hey, normal sinus rhythm.
03:32
That's why we have a P wave for
every QRS and everything is regular.
03:36
Atrial fib?
That's why it looks like
such a mess in that slide.
03:41
Because we have
this going on,
and we don't have a consistent SA
node, AV node down to the ventricles.
03:51
So let's review how
to analyze any strip.
03:54
First, we look at the
heart rate and rhythm,
then we look at the P
waves, then the PR interval,
the QRS duration,
the ST segment,
the T wave and
the QT interval.
04:07
So step one,
take a look at this strip,
like I want you to
actually practice with me.
04:13
You'll learn much more efficiently
if we do this together.
04:17
So we're going to look at
the heart rate and rhythm.
04:20
First, we identify six
seconds of a strip,
we count the QRS complexes
and multiply by 10
to calculate the
beats per minute.
04:28
So we laid out a
six second strip.
04:31
We counted the beats
and we have 10 beats.
04:36
So 10 QRS times 10 equals
100 beats a minute.
04:41
Now, we've seen these before,
but do you remember the name?
These are calipers.
04:47
Now calipers were the
original measuring tool,
but now you do it most often on
a monitor with digital calibers.
04:55
But this is what we
used to use old school
and still would work
just fine for you.
05:01
But we've looked at the
rate, we know it's about 100.
05:03
Now we're going to look at the
rhythm, is the rhythm regular?
Well, you would measure
between complex one and two
to determine if it's
the same distance
between one and two
and two and three.
05:15
Wow, you can tell by eyeballing
it that it is not the same,
but be diligent,
be systematic,
measure between one and
two, then two and three,
then three, and four.
05:27
So you have a really
strong feeling like,
Yeah, this is not regular.
05:34
Step two,
we're gonna look at the P waves.
05:36
So we don't have one clear
P wave present for each QRS.
05:41
And they do not
all look the same.
05:44
So it would be hard to
tell a regular PTP interval
because we can't
even measure it.
05:49
So we would not
call it regular.
05:51
Now in sinus rhythm,
a normal P wave or an atrial
contraction precedes every QRS.
05:58
You always start with normal,
and then compare what
you actually have.
06:02
Atrial fib?
No discernible P waves,
or an absence of discrete waves,
meaning waves that we
could tell our P waves,
sinus rhythm, P wave,
every QRS, atrial fib?
We got a mess.
06:17
So there's no
discernible P wave
or an absence of ones that
we can recognise as a P wave.
06:24
Now measure the PR interval?
What?
We can't.
06:29
If we don't have P waves,
we certainly can't measure a PR interval.
06:34
Now let's look at
the QRS duration.
06:37
Now we're going
to measure that
the same way to the best
of our ability, right?
Where the Q wave starts
off the isoelectric line
through the width
fest, the R and the S.
06:47
So the normal would
be less than 0.12,
or three small squares.
06:54
Remember, the small squares are
worth point .04 seconds each.
06:58
So if we have three of those,
we want to less than 0.12.
07:02
So measure the QRS
duration on the strip,
hey, don't look at the answer
that we're gonna supply for you.
07:08
But measure the QRS
duration on this strip,
while you pause the video and then
come back and check your answer.
07:19
Now step five,
we're going to look at the ST segment.
07:23
Do we see any depression
or elevation on this strip?
So we see where the
isoelectric line should be?
Does it look like that ST
segment is depressed or elevated?
No, not really.
07:41
Now we're going to try
and look at the T waves.
07:43
Remember, we want them to be
rounded and not peaked or tall.
07:48
Well just really kind
of have a mess there.
07:51
But you can somewhat
see them but
it's very difficult to see which is a
common characteristic of atrial fib.
07:58
That line in between the QRS
complexes is just kind of a mess.
08:02
Now, QT interval this would
be very difficult to measure.
08:06
So we know what normal
is, but it's really not
easy to do that on
atrial fibrillation
strip.
So when we're wrapping this up,
you're gonna see throughout
this video series,
we take a normal
sinus rhythm strip,
and then we compare the
strip we're interpreting.
08:22
So in sinus rhythm,
you've got a normal P
wave or atrial contraction
for every QRS complex.
08:28
Atrial fib,
no discernible P waves
or just a total absence of them from
what you're seeing on the strip.
08:36
Now as far as the rhythm goes,
the rhythms regular in sinus rhythm,
but it can vary slightly
when someone's...
08:44
breathing,
and atrial fibrillation is
irregularly irregular ventricular rate
for measuring QRS to QRS.
08:53
Now what about the rate?
While the rate ranges between 60 and
100 beats a minute in sinus rhythm,
and the rate can range
between 101-175 beats a minute
for atrial fibrillation.
09:07
Now that's when there's a
rapid ventricular response,
so the rate may
sometimes be lower.
09:13
So let's review why this strip
is actually atrial fibrillation.
09:18
The heart rate is
between 101-175,
the rhythm is irregular,
there's no discernible
P waves before the QRS.
09:27
The PR interval
can't be measured
and the QRS,
we're going to let you know is
about less than point one two.
09:35
Thank you for watching this
part of our video series.