00:01
We've made it to step six.
00:04
Can you pause for just a minute, and
remember the first 5 steps on your own?
Okay, I hope you did that
without looking at your notes.
00:19
Number 6 is to examine the T wave.
00:22
Now the T wave represents the repolarization,
or the relaxation of the ventricles.
00:28
We've got that highlighted for you in our graphic.
00:32
Now, the T wave should be rounded
and upright, but not tall, or peaked.
00:37
If the T wave looks abnormal, it may not be
pathological, but you definitely need to follow up
and do further assessment.
00:45
Take a closer look at that T wave.
00:47
I want you to become comfortable with
what they look like when they're normal.
00:51
Look at the first half of the T wave,
you'll notice it's a nice gradual slope,
then look at the last half, it's a lot steeper.
01:00
So T waves, normal T waves are not symmetrical.
01:04
There's nothing wrong with this patient's T wave.
01:07
We expect the first part to be a gradual slope,
and the last part to be a more steep slope.
01:14
Now if we're going to get real fancy here,
it's usually about 1/8 but less than
2/3 of the amplitude of the R wave.
01:23
That is a mouthful, you likely not have
to really use this on a regular basis
but we want you to know when your
eye notices something is off,
this is one way to specifically measure it.
01:37
So a normal T wave can be from 1/8, but
less than 2/3 of the amplitude of the R wave.
01:44
You remember how to measure
the amplitude of the R wave?
The isoelectric line all the way to the
top of the peak, which is the R wave.
01:53
Now when you measure the amplitude of the
T wave, it's still the isoelectric line
to the top of the T wave.
02:01
And that should be 1/8 of the amount or at least
less than 2/3 of the amplitude of the R wave.
02:10
Now the T wave amplitude
rarely exceeds 10 millimeters,
and the T wave follows the same
direction of the QRS deflection.
02:18
This is a positive QRS, right because
it's above the isoelectric line.
02:23
It's also a positive T wave because
it's above the isoelectric line.
02:29
Now peaked T wave, see the difference in
this we've given you different leads here.
02:34
So you can see what the T wave may look like.
02:36
This could be an indication of
an extra high serum potassium,
or maybe even an evolving MI.
02:44
Best takeaway?
If that T wave doesn't look normal, and
it's peaked, you need further assessment.
02:52
Now I've got some other examples here
about the T wave and potassium levels,
because this can be an indication
of hyperkalemia or high potassium.
03:01
But keep in mind, an ECG really isn't
that sensitive for hyperkalemia.
03:06
So you would want to have lab work to
check and see if there was a problem.
03:11
Profound hyperkalemia can lead
to heart block and asystole.
03:16
Okay, that's worth repeating.
03:18
Why do we get so worked up about potassium levels?
Well, if you start seeing some peaked T waves
that indicate it could be a potassium level,
it's always a good practice just to check even
though you know that's not absolutely definitive.
03:34
If you're getting a clue like
that, you always want to follow up.
03:39
We're real worried about potassium levels
because extremely high potassium levels
can lead to death, specifically heart block
and asystole and that would be the death.
03:51
Now the T waves appear peaked initially
with decreased amplitude of the P waves,
and then the QRS becomes prolonged.
04:00
So this is what you're going
to see in the progression.
04:03
You see there, how the wave changes, right?
So it progresses and the
changes that you're seeing
is the amplitude is getting shorter,
smaller, smaller, smaller, see that
from the first one down to the fifth one.
04:18
And then the QRS becomes wider and prolonged.
04:22
These are the types of changes you would
see as potassium level gets higher,
but know if you saw rhythm, that just
like one of those, you wouldn't know
what the exact level of the potassium
was, you would have to draw lab work.
04:36
Now what about an inverted T wave?
What makes the T wave inverted?
Well, if you look at this, the left example,
the T wave is the same
deflection, direction as the QRS,
but in the right one, it's different.
04:54
Now there's a range of reasons
that a T wave can be inverted.
04:56
The patient may be asymptomatic
and their heart is otherwise normal
but the patient could be experiencing
an evolving heart attack.
05:05
So the patient may have some structural
heart disease like coronary heart disease
or left ventricular hypertrophy, you
definitely want to follow up on it.
05:14
So the left one is what we
expect to see in most people
but the right one doesn't mean
they're in imminent danger
but you should follow up and get a closer
history of the patient and make sure you're aware
of their vital signs and how stable
they're feeling in your assessment.