What is going on guys? Don checking in, welcome to MINT, where we bring nursing to you.
So today, we are going to talk about the easiest way to interpret your heart blocks but before we start,
if you haven't it already, I highly recommend that you guys watch our EKG interpretation video.
That video contains important concepts about EKG and the conduction system of the heart that will
hopefully make today's topic easier to understand. If you're ready, I'm ready, let's get going.
Hello guys. This is how you're going to interpret your heart blocks. First and foremost, what causes
heart blocks? In heart blocks, the problem lies within the conduction system of the heart. The
block may be found between the SA node and the AV node or the problem can be found between the
AV node and the Bundle of His, all the way to the Purkinje fibers. Common causes of heart blocks are
scarring of the cardiac cells due to aging, heart attacks, valve infections caused by endocarditis,
and some medications such as Digoxin. Whatever the cause is, do know that they affect the conduction
system of the heart and they cause your EKG to change. There are four types of heart blocks
and we're going to talk about them one by one and we're going to emphasize specific characteristics
about them. First up, first degree heart block. In your first degree heart block, there is a partial
block between your SA node and your AV node. It is partial because even though there's a block here,
the impulse still goes through all the way to the Purkinje fibers. There is a delay somewhere here,
but it still goes all the way. In our EKG, this will cause a consistent prolonged PRI or PR
interval. Note the word consistent. And just a review, our normal PR interval is between 0.12
to 0.20 seconds. So first degree heart block will look something like this. Sometimes,
just by looking at your PRI, you can tell that the PRI is prolonged but the best way to know
if your PRI is prolonged is when you measure it. So for this EKG, there are a one two three
four five six seven eight nine small boxes times 0.04 seconds, your PRI for this EKG strip is 0.36
seconds. That is pretty long. Our normal is only up to 0.20 seconds. If you measure your other PRI,
they are consistently long, the same measurements. That is your first degree heart block,
consistently prolonged PRI. Next up, would be our second-degree heart block type 1. This is
also known as your "Wenckebach". In your second-degree heart block type 1, there is
a progressive block between your SA node and your AV node. And I emphasized the word progressive.
So it starts with a normal conduction right here because there is no block, then eventually there
would be a partial block that will occur, then the block becomes more prominent, and eventually
there would be a complete block between your SA node and your AV node. In your EKG,
you will have a progressively prolongation of your PRI and a drop in your QRS. Your key words here
are progressively long PRI and your QRS will drop. So we begin with a normal PRI because initially,
there is no block present. But then, when the partial block takes place, the PRI gets longer;
there would be a delay from the conduction from the SA node all the way to the Purkinje fibers. As
the block continues to progress, the PRI gets even longer. Eventually, when the complete block takes
place, the QRS drops. So as you can see, there's a P wave here, there is no QRS complex. Then the
cycle begins again. So this is your second-degree heart block type 1. You can remember this type
with the term, "long, long, drop". This means that the PRI progressively goes longer then the
QRS drops. So "long, long, drop". Next up would be your second-degree heart block type 2. This is
also known as your "Mobitz II". In this heart block, there is an intermittent block between
your SA node and the AV node. Note the solid line, this means the block is complete not partial but
complete. As a result, the EKG will show drops in your QRS complex. Your word here is "drops". So
let us take a look. As you can see, when there is no block yet, you will start with a normal
EKG rhythm. However, once the block takes place, the QRS drops. As you can see, there's a P wave,
there's no QRS complex. See, there's a drop here and there's a drop there. There's P wave, T wave,
and your P wave again. This is your second-degree heart block type 2. And the way you're going to
remember this is "normal, normal, drop". This refers to the normal PRI's before your QRS drops.
Next up would be your third-degree heart block. This is also known as your complete
heart block. Complete heart block takes place between the atria and the ventricles, meaning
your atria will contract independently with your ventricles. What this will do to your EKG is that
your P waves will have no correlation with your QRS complex. This is what it is going to look
like in your EKG. You have P waves that march, meaning, they will have the same distance. There,
there and there, there's a P wave here but it's covered by the QRS complex. Also, you will have
QRS complex that will march as well, the same distance, however, there is no correlation
between your P waves and your QRS complexes. P waves occur because the atria are contracting
and your QRS occur because your ventricles are contracting but they are independent
with one another. This is your third degree heart block. And the way you're going to remember this,
is that your P waves march and your QRS complexes march but there is no correlation. Another hint
that you will have when it comes to third degree heart blocks is that most are super
bradycardic. So if you see a super bradycardia rhythm, look at the P's and the QRS complexes,
march them. No correlation? That is third degree heart block. As a review, first degree heart block
would be consistent prolongation of your PRI. Second-degree heart block type 1 would be "long,
long, drop" where your PRI gets longer and longer and then your QRS drops. second-degree heart block
type 2 would be "normal, normal, drop" where PRI would stay normal until the block takes place,
then the QRS complex drops. Your third degree heart block, your P waves and QRS march but there
would be no correlation. Plus usually, they're super bradycardic. That's it. Alright guys,
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