Myocardial Infarction / STEMI on ECG – Practice EKG


well welcome to another MedCram lecture
we’ve got another EKG that we want to go over and with this case this is a
patient that presents to the emergency room via ambulance for chest pain that’s
been going on for about 45 minutes and this is the EKG that is done in the
field you quickly review it and you notice that there is a report from the
field of a ST segment depression here in the precordial leads now this was done
about 10 minutes ago the patient is quickly moved into another room and an
EKG is done and here is the EKG that you get let’s go through our evaluation as
we go through this remember our five-step process here the first thing
that we want to look at is rates we can pick the easiest place to look at which
is the QRS complex here for instance we’ll look at these two and we can see
here clearly that we’ve got one box two boxes three boxes and then four and
maybe a little bit extra again let’s look at another one up here we can look
at the tier one two three four and a little bit more so as we’re looking at
that remember we go through the counts the first box is going to be 300 the
second box is going to be 150 the third box is good to be a hundred the fourth
box is going to be 75 and so this is going to be somewhere between 60 and 75
so we can come up with something for instance 70 now if we look over here on
the other side of the page we can see clearly if we count it through that
we’ve got one two three four five boxes so here it’s going to be 300 150 175
and then finally sixty over here on this side so whereas over here it’s probably
around 70 over here it’s probably more around 60 and it looks as though
something happened right about here where there was a change now remember
that the entire strip is about ten seconds and so if we count up the number
of QRS complexes and multiply it by six we’ll get how many complexes there are
in about a minute so let’s take a look here we have one two three four five six
seven eight nine ten so multiply ten probably and a little bit more here
times six and we’re gonna get a little bit more than sixty somewhere between
sixty and seventy which is exactly what we come up with so for us the rate is
somewhere between 60 and 70 beats per minute all right next let’s go on to
rhythm so the best lead to look for rhythm is Roman lead two and that’s this
one down here usually it’s the rhythm strip and that’s aptly named that way so
we’re going to look for each QRS complex here and we’re going to look to see
before the QRS complex if we see p-waves and we can clearly see P waves before
each QRS complex here’s another QRS complex here’s the P
wave QRS P wave we don’t see extra P waves although there is this little
extra beat here and you probably can figure out what that is that’s probably
a u wave sometimes associated with low potassium but clearly we see here that
there is P waves before each QRS complex and so we’re gonna call this sinus
rhythm great next let’s look at axis so again like we talked about in previous
videos you can look at these leads here and see which one is the most positive
and the highest in amplitude and in this case the one that we’re looking at here
is Roman numeral lead 2 you can see that it’s the highest in amplitude so
remember the direction remember 2 is going down sharply in this direction
whereas 3 is going down sharply in this direction AVL is going to the left hand
side and so it’s going to be going up in this direction a V F of course is going
straight down Roman lead 1 is going straight across and AV r of course is
going off at that type of an angle so if we see that the highest one here is
going in this direction then that’s the closest to where it’s going now the
other way of looking at this is to see which one is the most isoelectric and we
can see here with lead 1 that that seems to be the most isoelectric so it’s gonna
be very perpendicular to Roman numeral lead one because it’s isoelectric but
it’s going to be going almost parallel to Roman numeral lead 2 and so in fact
the probable way that this is going is in this direction now if that’s the case
it should be positive in lead 3 because it’s going almost in the same direction
and that’s the case since it’s going almost parallel to a VF it should also
be positive and in fact it is now because it’s going almost in the
opposite direction to a VL this is going down and this is going up it should be
negative and it is but it should be the most negative link compared to a V R
because it’s going almost in the opposite direction and that’s where you
have the biggest negative discharge so the overall axis if we consider that
this is 0 degrees here somewhere between 60 and 90 degrees and that takes care of
access let’s move on to hypertrophy so again the big things that we’re looking
for for hypertrophy is the right atrium and for the right atrium we look at
Roman numeral lead 2 but we could also look at pre quarter lead v1 and we’re
looking at whether or not there is a large up and a small down or whether or
not there is a small up and large down the big up remember is the right atrium
and the big down is the left atrium and of course we’re not seeing that here we
don’t see that in lead 1 so let’s start from the beginning right atrium should
have a peaked P wave we don’t see that there right atrium should also have a
large positive component in the P wave in lead v1 we don’t see that so right
atrium is a negative let’s go on to the left atrium as we mentioned the left
atrium should have a large negative deflection we may be seeing that a
little bit here but it’s got to be bigger than a box so we’re not seeing
that much so no on the left atrium now the right ventricle we also look at lead
v1 and in lead v1 we should have a R wave the positive component of of this
that is bigger than the S wave and that is actually looking like we might
actually have that if we measure this out we can see that the R wave may be
slightly larger than the S wave so we may have some right ventricular
hypertrophy here it also looks like we’ve got a little bit of a bundle
branch block pattern here as well now let’s go to the left ventricular
criteria now for that we need to look at the S wave in lead v1 and here it’s
about 5 millimeters and we also need to look at the R wave in lead v5 and here
we’re looking at 5 10 15 20 so that’s 5 times 1 2 3 4 so
here we have about 20 so we add the 20 millimeters and the 5 millimeters
together and we come up with 25 however that’s still not enough for the criteria
of 35 which is what the criteria is for left ventricular hypertrophy so after
all of that we have some questionable are the hypertrophy good now let’s go
onto st-segment I think we can all clearly see that we’ve got some ST
segment elevation in the precordial leads whereas before when the patient
first came in to the emergency room there was some ST segment depression
now there’s ST segment elevation if you look back at the first EKG you’ll notice
something that’s really interesting in AVR specifically ABR is a very specific
lead and it’s important in that it looks directly at the endocardium notice here
very carefully that you actually see some ST segment elevation although it is
mild this ST segment elevation usually means in AVR that myocardial injury is
in sipping it’s coming it’s an ST elevation mi precursor if you will so if
you see this ST segment elevation be very very concerned and you can see here
that this is kind of giving it away in the sense that you’ve got precordial
leads with ST segment depression and you’ve got this AVR with ST segment
elevation now be aware that if you see ST segment depression in AVR that along
with tachycardia is usually going to mean pericarditis but that’s not what we
see here we see ST segment elevation and now on the second EKG notice in addition
to our ST segment elevation that we already talked about look here again AVR
with significant ST segment elevation and this in the appropriate clinical
setting which is we typically see is consistent with and
concerning for an ST segment elevation myocardial infarction so generally what
you want to see is two contiguous leads with greater than 1 millimeter ST
segment elevation the criteria actually for v2 and for v3 is actually a little
bit more stringent and for men that are 40 plus the criteria is actually 2
millimeters and for men that are less than 4 it’s even more stringent at 2.5
millimeters for women it’s actually just 1.5 millimeters and here depending on
where you draw the baseline there is maybe not quite 2.5 millimeters but
certainly on its way to being that in this patient and if you look at some
other criteria here with v1 and also what we talked about with AVR this is
highly suggestive of myocardial injury now because these are in the precordial
leads we’re looking at right ventricular precordial and anterior left ventricular
notice we don’t see them going over to the lateral leads here
and so the answer here is yes there is elevation and that is consistent with a
ST segment elevation myocardial infarction okay let’s briefly talk about
the management of this because this patient has a myocardial infarction the
patient needs reperfusion therapy and this can come in two different ways one
is through what we call pci percutaneous catheterization otherwise known as
percutaneous coronary intervention and the other is thrombolytics and this should be considered if the
patient doesn’t have any contraindications and if the patient’s
been having chest pain for less than 12 hours now you should know that PCI is
considered to be the superior technique now there’s two different options number
one is that you have PCI at your facility and the other option is that
you don’t have PCI now if you have PCI the goal is to get your patient to the
cath lab and have them inserting the catheter in ninety minutes that is a key
number that you should be aware if you don’t have a cath lab then you need to
get them there within 120 minutes that is another number that you should be
aware of is the 120 minute number the reason why this is important to
understand is that if you cannot do this if you cannot get the patient to either
your cath lab in 90 minutes or another hospitals cath lab in 120 minutes then
the other alternative to do is thrombolytics now you may still have to
transfer the patient for rescue percutaneous coronary intervention but
in terms of primary PCI you need to know those numbers because that is the
treatment for this and be aware of the contraindications for thrombolysis which
we won’t get into in this lecture thank you for joining us you

4 thoughts on “Myocardial Infarction / STEMI on ECG – Practice EKG

  1. Thanks for watching! Please subscribe and join Dr. Seheult for the rest of the ECG video series at: https://www.medcram.com/courses/ekg-ecg-interpretation-explained-clearly

  2. Are you a professor at Harvard university?
    If not, I think you should because you are amazing!!. This is what the students need in college. A first class professor. Thank you

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