ECG Interpretation Explained Clearly and Succinctly – Arrhythmias, Blocks, Hypertrophy…

By Adem Lewis / in , , , , , , , , , , , , , , , , , , , , , , , /

welcome to EKG explained clearly by the
end of this course you’ll have all the skills needed to confidently interpret
EKGs in a systematic way you’ll understand the electrical activity
represented on EKG paper that allows this process to happen the heart to beat
and cycle blood through our lungs and bodies this is the final product whether
or not you have experience with EKG interpretation I think you’ll find this
series of videos very useful if you understand the key foundations of how
the heart works it’ll be much easier to learn and remember the nuances involved
with the EKG that we’ll cover later in this course so we’ll start with the
anatomy and physiology of the heart depolarization repolarization and then
on to leads and specifics about EKG paper and how a tracing is captured next
are specifics on EKG tracing the P wave the QRS complexes the QT interval the
r2r interval etc we’ll cover the impact of our nervous system and
neurotransmitters on the heart then on to rate rhythm axis escape rhythms PVC
bigeminy tachyarrhythmias ventricular tachycardia and the key differences
between ventricular tachycardia and paroxysmal supraventricular tachycardia
with aberrancy the QT c and the potentially life-threatening Prasad’s
the points atrial fibrillation and flutter widened QRS complexes and the
various types of heart blocks using precordial leads to hone in on certain
areas of the heart atrial enlargement and ventricular hypertrophy acute
coronary syndromes myocardial infarction and pericarditis we’ll talk about T
waves ST segment and T wave changes that we see with ischemia bundle branch
blocks and vesicular blocks and then at the end we’ll put it all together and
teach you how to systematically read an EKG we’ll go through a normal one first
and then on to a variety of abnormal EKGs liked sinus tachycardia atrial
fibrillation multifocal atrial tachycardia first second and
third-degree heart blocks h’lo largeman tricular hypertrophy x’ hyperkalemia
rare anomalies and many many more abnormal
EKGs so let’s begin with anatomy this is a animation here of the heart beating
and there’s a number of things that I want you to see so you’ll understand
this when we talk about the conduction system of the heart and the EKG so the
EKG as you know is a way of looking at the electrical activity of the heart and
it’s really the electrical activity of the heart that is responsible for what
we’re seeing here right now just for those that don’t know the anatomy of the
heart we’ve got the right ventricle here on this side we’ve got the left
ventricle here on this side and these areas up here are the atria so this is
the right atrium here and the left atrium is over here interestingly here
what we’ve got is the tricuspid valve this is a valve that allows blood to
flow in from the right atrium into the right ventricle and then gets pumped out
through the pulmonic artery and this is the pulmonic valve here the semilunar
valves as you can see and then what you can’t really see very well is the aortic
valve which is here at the top and this is where the left ventricle is pumping
out into there now one of the things that I want you to notice first off is
if you look carefully you’ll see that the right atrium here beats before the
right ventricle right atrium right before the right ventricle and you’ll
also notice similarly that the left atrium beats right before the left
ventricle now this is because of the anatomy of the conduction system there
is an electronic conduction system in the heart that is not made up of nerves
but instead of modified specialized myocardial sites okay up here is the
sinoatrial node which because of its relatively quick activity is the
pacemaker for the whole heart it then goes to the atrial ventricular node
which is here and then goes down this conduction system here called the hiss
Purkinje system and as you can see it goes up and it basically conducts the
electric signal to the myocardium now we’re gonna talk more about this in
detail but I wanted you to notice that it’s this conduction system that
basically makes this movement that we’re seeing right here like a perfectly well
timed Symphony depends on the analogy that you want to use there are several
different analogies that you can use the conductor that is conducting a symphony
and you want to make sure that the violins and the cellos and the flutes
and the viola and the timpani they’re all acting all at the same time so you
get the maximum effect in other words everything is working in concert the
other way of looking at it is a little bit more destructive you know that if
people are trying to demolish a building they will have certain areas of the
building that are drilled out and weakened with sticks of dynamite and
when they activate that dynamite it has to be activated in just the right order
in just the right fashion so that the building comes down right on top of its
footprint well this is kind of what’s going on here with the heart this
electric conduction system the sinoatrial the atrioventricular and the
hiss Purkinje system is activated in such a way that the electrical
conduction goes and stimulates the heart in concert so the electrical conduction
starts up here and then goes to the ventricle the reason for that is so that
the atria contract right before the ventricle the purpose of that is to get
the blood from the atria down into the ventricle to increase the size of the
ventricle right before the ventricles contract that causes an increase in
freeload and allows your cardiac output to be improved that’s happening on both
sides so you can see that the atria are contracting first and then the signal is
placed down here to the history Kinji system it travels down very quickly down
this hiss Purkinje system and then up here into the myocardium so the effect
is is that essentially the myocardium is contracting all at the same time and you
want that to happen instead of having contraction occurring
from the top down you want contraction occurring all at the same time because
of this very unique conduction system this is going to look very unusual
or look very unique I should say on an EKG what is an EKG it’s a way of
measuring current you know that when you take a battery and you place it on a
voltmeter if you put the positive end to the positive meter and the negative end
to the negative meter you’re going to move the dial up so that you see that
there is a difference in the voltage when that voltage starts to move that is
when you have an electric current and so what an EKG does is it sees how is this
depolarization or this movement of positive charges that’s going down the
hiss Purkinje system how does it look from the electric vision if you will in
other words if I have an ultrasound machine I could see if there is fluid or
fluid moving on the ultrasound what an EKG does is it does exactly the same
thing except instead of fluid moving and objects that you could see you’re seeing
electricity moving and so that is what we’re going to look at today atria
contract first then ventricles contract second but they’re contracting in
concert and then what happens is everything resets back to normal and you
have the same contraction happening again the next series that we’re going
to talk about is we’re going to break things down to the smallest level and
then we’re going to build it up so that we can finally see how we get back to
this point again okay so zooming in a little bit more now
in terms of where we were let’s pull away all the muscular
activity here and let’s look specifically at this conduction system I
want to be very clear the thing that you’ve got to understand that these are
not nerves okay these are modified myocardial cells
that conduct electricity very quickly and we’ll talk about how that happens so
the first one that you’ve got to know is the sinoatrial node it is at the very
top and the reason why it is there and as the pacemaker is because its
intrinsic activity is the fastest and since it is the fastest it’s going to
cause depolarization to occur all the way down and everything else is going to
have to be in concert so this is kind of the conductor of the concert now there
are different pathways to get to the AV node you can see here that the SA node
can to the AV node now the AV node is right
here and it kind of holds things up it kind of delays things we’ll talk about
that in another lecture so that what you have here is you have the sinoatrial
node saying okay it’s time to contract and we’ll talk about how that happens
and the atria contract and then the electrical conduction gets down to here
and it holds up what that effectively allows the heart to do is to pump blood
from the atria down into the ventricles and allows it the time to pump it member
this happens so quickly SA node to AV node then when the blood is in the
ventricle the AV node then conducts this depolarization that’s occurring into the
Hispano system and it travels down and around so quickly so very quickly that
essentially the entire myocardium that this innervates okay or that it
penetrates basically depolarizes almost all at the same time so that again is
sort of a map of this cardiac conduction system and really it’s this cardiac
conduction system that allows the depolarization to occur in such a nice
and timed way now on an EKG when we’re actually looking at the electrical
depolarization are we actually seeing the electrical movement down this
conduction system the answer is no this is such a small amount of electricity
that it’s almost imperceptible on an EKG what is it that we’re actually measuring
what we’re measuring is the depolarization of the muscle the
depolarization of the muscle is very large and amplitude and that is what we
are picking up on the EKG kind of like if we are demolishing a building what do
we see on the video do we actually see the electricity going into the wires to
the dynamite no we’re actually seeing the dynamite blow up and the building
coming down that’s in other words what we’re seeing on the EKG even though
there is electrical conduction going down this what we’re seeing electrically
on an EKG is the depolarization of the actual muscle cells
so just be aware of that okay so to get a little bit more of the insight about
what’s going on let’s go down to the microscopic level and I want to show you
a myocyte here now the thing that you should know about a myocyte is just like
any other skeletal or smooth muscle cell it has a collection in it called the
sarcoplasmic reticulum we’ll call that SR and the SR is full of calcium and the
reason why it’s full of calcium is because this calcium can be released
into the cell upon depolarization of the cell we’ll talk about that and that’s
gonna cause contraction of the striated muscle so we’ll just put a bunch of
muscle cells here it’s going to contract okay and if you were to look
histologically at the areas of the myofibrils that are in cells you’ll see
how muscle cells work but basically calcium is what’s going to activate them
to contract and they’re made up of troponin and all of these other things
that we won’t get into the key here though is the sarcoplasmic reticulum
causes calcium to be released and that’s what triggers it the question is is what
triggers the sarcoplasmic reticulum well what happens is as you may know on the
cell surface of these cells you have a sodium potassium pump and the purpose of
that is to pump sodium out of the cell and as you know sodium has a plus one
charge and at the same time pump in potassium and potassium has a positive
one charge but it pumps out three sodium for every two potassium and so what ends
up happening is is there’s a very high concentration of sodium okay one plus
outside the cell and there’s a very high concentration of potassium inside the
cell now as it turns out the cell is very important so sodium stays very high
outside of the cell the way of thinking about it is because three are going out
and two are going in there is a negative charge on the inside of the cell okay
negative charge on the in of the cell and there are positive
charges if you will on the outside of the cell we’ll ignore those for now
because the outside of the cell is very very large and the inside of the cell is
very very small so as a result of that there’s a far more negative charge that
we see here now the other thing that’s important to know is that the cell while
it is very important it is very permeable to potassium and as a result
of that potassium leaks out somewhat now as it leaks out it’s losing a positive
charge so that even makes it more negative and as a result you have a very
negative resting potential on the inside of the cell now with that basis of history let us go
forward here in the next lecture and talk about why this interior negative
charge is so important to the electrical conduction that we’re going to talk
about here in our EKG course thanks for joining us

6 thoughts on “ECG Interpretation Explained Clearly and Succinctly – Arrhythmias, Blocks, Hypertrophy…

  1. This is a perfect recap for medical students! It is a very informative video, and easy to understand!

  2. Join Dr. Seheult for the complete ECG Interpretation video series:
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  3. Any chance I'm lucky and you have some sort of discount for this EKG series? I'm about to purchase and would love a sweet deal as I finish my last year in medical school. Either way, LOVE your videos

  4. I am a nurse but not working I like your lecture but don't have money and watch…So.Pls give free presentation. Thanks

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