Welcome to another MedCram lecture we're gonna talk about this EKG and try
to get to the right diagnosis so this is a 48 year old gentleman who presents to
the emergency room with about a 24 hour onset of progressive dyspnea shortness
of breath and chest pain our meticulous organized way of going through this EKG
is as we recall rate rhythm and then access and then we'll get to the special
things at that point so the first thing we want to do is figure out the rate and
I've left some of the numbers up here so we can check it later I've also left the
interpretation on this EKG the first thing we want to do is look here at the
QRS and lead one and you can see here that it starts right at this box and
there's a little bit of space between there and here so if we count up those
boxes we get about two and a half boxes so when we know the number of boxes
between the QRS complexes we simply take 300 and we divide it by 2.5 boxes and
the number that we get is equal to about 120 and that's going to be our
ventricular rate and so we confirm here that the ventricular rate is actually
118 so we're pretty close so that's the rate the next thing we
need to do is figure out what the rhythm is and we can see here clearly before
each QRS is a p-wave and we don't see any intervening p-waves around it or
through it and so this is going to be a sinus rhythm and because there's a
tachycardia because we are greater than 100 beats per minute this is going to be
a sinus tachycardia and so we get the first diagnosis correctly the next thing
we need to do is to look at the axis so let's review axis again remember with
axis we've got a circle and zero degrees is out here at the far right and we go
around this direction in a positive sense and we go around this direction in
a negative sense and remember that generally speaking the normal axis is
going to be in this quadrant down here there are several ways of looking at
this and if you go through the EKG course
I am calm we'll go through different techniques of having to do it probably
the simplest way is to look at the axis leads on the EKG that are already
aligned at the 90 degrees position and also the zero degrees position so the
one that's aligned at the zero degrees position is the lead Roman numeral one
and that is this lead right here if anything is positive in that lead then
it's going to be going positively towards this zero position however if
the QRS is negative in this position it's going in exactly the opposite
direction this is the negative for lead one and so what is the ventricular axis
by looking at the QRS complex we can see clearly here that the majority of that
QRS complex is in the negative position in fact if we were to measure in terms
of amplitude it's about one large box down so in that case we know that our
axis and I'll do it here in red is going to be predominantly in this direction
which is abnormal this is not normal normally we have a left-leaning axis and
in this case we don't so let's keep going and see so what we want to do is
not only look at here at the x axis but we want to look at the y axis the axis
that's aligned at 90 degrees right here and so for that we're going to look at a
VF a VF is the one that is aligned going down in this direction so again we look
at the QRS complex if it is going up then it's generally going to be in the
positive direction and if it is going down it's going to be in the negative
direction up here clearly we can see or approximately about the same as a box it
is going up so in this case we're going to have a positive deflection because
this QRS is going up and so therefore we will draw the resultant going down so in
other words our axis is going to be somewhere in between these arrows so
it's gonna be in that quadrant and if you look at this there are just about
the same I think you would be able to say that the a VF positive amplitude is
a little bit bigger than the negative amplitude in lead one
because part of this is actually going up and it's taking away from that vector
so I would say overall and I'll put this in blue or in purple so we can see here
that it's going to be closer to the 90 then it would be to the 180 and so I
would say overall that the vector here is going to be in this direction which
would be around 120 degrees or even a little bit more maybe even to 135
degrees so let's check and see here P axis and our axis and a t axis we're
interested of course in the r axis which has to do with the ventricle and in this
case the computer agrees that we're at about 120 all right so we got rate rythm
and axis okay for just clarity sake I'm going to go ahead and erase all of this
and we're gonna start looking at some special circumstances we have already
shown that we've got a sinus tachycardia with a right axis deviation one of the
concerns that we have in this patient who's young he's 48 is myocardial
infarction but the other possibility is a pulmonary embolism if this is a
myocardial infarction we would be concerned in a right-sided
ventricular issue because we've got a right bundle branch block pattern the
other thing that we have talked about and we talked about in our course on
EKGs and also on pulmonary embolism are the certain and specific EKG findings
that we see in pulmonary embolism now we say specific but they're actually not
specific for so that you could actually make a diagnosis of and they're not
sensitive so that if they're missing you could rule it out but they are
associated with pulmonary embolism and cor pulmonale which is when you have an
increase in right ventricular pressure so what are the things that we see
occasionally well the one that is classic but probably you should not take
to the bank but you should probably know what it is is called an s-1 q3 and then
I'm gonna write this as an upside-down T and you'll see why here in a second t3
so this s-one q-three t3 has kind of been classically described in the
literature as being associated with right-sided pressures and we have a
similar example to that here in this case although the Q is not as good
that should be but let me show you here the Roman numeral one is this one right
here and you can see clearly here that we've got a fairly large s wave in lead
one and that's what gives us s one the next one is going to lead three Roman
numeral three which is right here and generally you should see a little bit
more of a q wave than you're seeing here I'll draw one end so you can see what
I'm talking about so you should see more of a q wave there you're not it's small
but nevertheless that's what you should see and then the next big thing that you
should see is a upside down or flip T wave in lead Roman numeral three which
you can see very clearly right there so what we have here is kind of a s-one
q-three t three but something else that is seen in pulmonary embolism that we
talked about also in our course is the flipped T wave in the precordial leads
this shows a right ventricular strain pattern and of course it's showing up in
the precordial leads because those are the leads that look best at the right
ventricle and you can see that very clearly here as it turns out this
patient did have a very large pulmonary embolism and it was picked up pretty
quickly here on the EKG
and anticoagulation was begun the two things about pulmonary embolism
you can sometimes pick it up on EKGs very quickly you want to make the
diagnosis quickly and you want to think about pulmonary embolism because almost
all of the tests that are run and give you a diagnosis of pulmonary embolism
are specific for pulmonary embolism so a CT angiogram is specific for pulmonary
embolism a VQ scan is specific for pulmonary embolism a d-dimer is
something that you order when you're thinking about a pulmonary embolism the
point here is that unless you think about a pulmonary embolism you will
never make the diagnosis of a pulmonary embolism the other thing I want to make
clear here as well is that a methodical prescribed method of going through EKGs
will give you things that you might not always see if you just glance at the EKG
so make sure you go through in a systematic way so the second thing as I
mentioned here is flipped T waves in the precordial leads you might also see that
remember in myocardial infarction which is in the differential diagnosis so make
sure that you are thinking about these things and if you want more information
on this head over to med cram comm where we have a EKG course which will give you
continuing education credits and also a pulmonary embolism course that goes over
the epidemiology the diagnosis and the treatments with the new oral
anticoagulation medications and also discussing the antidotes for those
medications now thank you for joining us
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