Now, it's important to go through an ECG step-by-step
and name the various waves.
And you might be familiar with
some of the naming of these waves,
but let's go through them again,
so everybody's on the same page
because we have this down,
then we can add pathology later on.
But until you know the waveforms,
we can’t get to that point,
and that's the fun part.
So, now you have to learn the waves.
The first is the P wave.
The P wave corresponds to atrial depolarization.
So, that’s the top part of the heart depolarizing.
The next thing we have is
called the PR interval,
and so that is from the start of the P wave
to the start of the QRS complex.
The QRS complex is ventricular depolarization.
So, as you can imagine,
the top part of the heart depolarizing is important, right?
But, really, where are you pushing
the blood from the top of the heart?
Just to the bottom part of the heart.
Where are you pushing the blood
from the bottom part of the heart?
Out throughout the whole body
or all through the lungs.
So, it’s a longer distance you are pushing
the blood out as you go through the ventricles.
That's why the QRS complex is so important
because it's pushing blood out
throughout the whole body
or throughout the lungs.
The next interval we have is called the QT interval
and that goes from the start of the QRS complex
all the way to the end of the T wave.
We have something called the ST segment.
The ST segment is from the end of the S wave
to the start of the T wave.
And the final thing we have
is called the T wave
and the T wave is the
repolarization of the ventricles.
In certain pathologies, there's another little bump
after the T wave, called the U wave,
but that only occurs in pathology.
So, our primary things,
and T wave.
So, let's go through these processes
even in more detail
and add some intervals to them
besides just the PR interval and the QT interval.
The biggest one is called the R-R interval.
And the R-R interval takes from one R wave
all the way to the next R wave.
This is an important interval
because this determines
how often your ventricles depolarize.
What should this tell you?
It’s how fast the heart is beating,
how many times it depolarizes.
So, the R-R interval is how
you base heart rate on.
The PR interval,
we already discussed,
is from the beginning of the P wave
to beginning of the QRS complex
and that needs to be a certain duration.
If it's longer than that,
then you might have an AV block.
The QRS has a certain duration that it needs to be.
If it’s too wide,
you're concerned about things like
premature ventricular complexes.
The QT interval is going to be very
dependent upon heart rate itself.
So, how often you have depolarization
versus how often it repolarizes.
The ST segment should be isoelectric,
meaning that should be a flat line
and it should match the same flat line
that’s after the T wave
and before the P wave.