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