welcome to another MedCram lecture we're going to talk about pulmonary
embolism and as you can see here on our CT scan here is the embolus right in the
middle of the pulmonary artery and the question is is why is it there how to
get there and what do we do about it now this video series contains a lot of
information and charts that I want to move through efficiently so we're gonna
do something a little different I'm gonna mix in some background slides that
I'll illustrate on so what we're gonna talk about is the epidemiology the
diagnosis treatment and treatment involves a number of different aspects
including assessing the stability of your patient what kind of medication do
you want to start how long do you want to start for if they're gonna be IVC
filters or not some newer techniques and then we'll talk about complications so
in terms of epidemiology a couple of things to keep in mind that we see this
in about a hundred out of a hundred thousand cases and slightly higher in
males and as you get older the risk is gonna go up especially after the age of
75 there's about a hundred thousand deaths per year in the United States
although the death rate is decreasing because we're getting better at
detecting it and treating it appropriately and now the risk ratio has
gone from 138 down to about 36 in the last 30 years the 38 mortality is four
and 13% for one year it's a common disease you should know virchow's triad
and they are number one venous stasis number two and the filiol injury and
number three hyper coagula bolused eight so one of the things that you've got to
realize about the diagnosis is that it's easy to miss in fact there was a spanish
study that showed it was misdiagnosed in one of three IDI patients and a
retrospective review of pulmonary embolism and over 400 patients they
found that 146 had a delayed diagnosis some of the things that increase the
risk of the diagnosis of course was hemoptysis
so anytime you see someone coughing up blood you got to think of pulmonary
embolism COPD you know that's one of the things that we would look for a the guys
got COPD maybe he doesn't have a pulmonary embolism maybe his shortness
of breath is from something else actually that still increases the rest
so don't be fooled by if patient has COPD pleuritic chest pain of
course is pretty classic for pulmonary embolism it increases the risk by three
point six asthma believe it or not cough all of these things could increase the
risk of a delayed diagnosis why because we're thinking about all of these other
possibilities now even though there was a delayed in diagnosis in this there was
no statistically significant increase in mortality with that delay in diagnosis
so in terms of diagnosis this is kind of the money slide when it comes to
figuring out what the patient has and what to do about it one of the things
that you've got to look at is how likely does the patient actually have it and
you don't want to use the wels criteria for that or the modified wels criteria
basically what it is is you're going through and you're assigning points
based on what you see so the patient has clinical signs of DVT like leg swelling
pain with palpation the patient gets assigned three points so what this means
when it says that the PE is more likely than another diagnosis is really let's
flip it around and say is there something else that's more likely other
than a PE for instance if you've got elevated neck veins and swelling in the
lower extremities and you've got curly B lines on the chest x-ray well maybe
we're dealing with congestive heart failure probably more likely than that
of a pulmonary embolism if the patient's got fevers night sweats chills and
they've got to elevate a white count they're coughing up yellow sputum and
they came in last week for a pneumonia then you know pneumonia is probably more
likely than a pulmonary embolism right so if the patient's got a pneumothorax
then pneumothorax is probably more likely to explain the clinical symptoms
of the patient more likely than a pulmonary embolism so in other words if
you see a diagnosis that stands alone by itself and it's probably contributing to
the signs and symptoms that we see then go with that diagnosis and don't give
the three points for a pulmonary embolism but on the other hand if you're
seeing all of these signs and symptoms like tachycardia tachypnea shortness of
breath and you don't see a pneumonia you don't see a pneumothorax you don't see
congestive heart failure that's when you apply the three points the PE is more
likely than some other diagnosis if they have a prior history of any kind
of clot 1.5 a heart rate greater than 100 gives them 1.5 if they've been
immobilized for three or more days that's another 1.5 if they've got
hemoptysis or I've got malignancy that gives you another point so you add them
up and if it's four or less the diagnosis is considered unlikely if it's
5 or more it's considered likely and so what you do with those points is you
determine what kind of tests you're going to get and we'll talk about that
but here on the right side are the gamut of tests that are usually ordered now
notice something about these tests the first thing that you'll notice is that
these are tests that are ordered specifically if you're thinking about a
pulmonary embolism notice that none of these tests are really done routinely so
you're not going to ever be surprised in the morning when the test comes back
positive for PE whenever you get a positive test for PE it's because you've
thought about it and herein lies the real crux of the problem with PE is that
if you never think about it you'll never really make the diagnosis
so let's talk about these CT angiogram this is where a patient goes into the CT
scan they have to hold their breath for about 10 seconds or so and the scanner
quickly gets these images that looks specifically at the pulmonary artery so
these are great tests if it is a large PE and if it's central what I mean by
that it's it's big it's in the large central pulmonary arteries not gonna be
so good if it's chronic and if it is in the peripheral vasculature because the
radiologist has to actually see the PE therefore it's pretty specific so it's
central and you got to be careful however of the GFR because you got to
give contrast to these patients so the kidney has to be able to take that
contrast okay so if you've got bad kidney function you can't use this test
the next one that's used it's a little bit older is a VQ scan also relatively
specific it looks better at peripheral so this is the test that you want to use
if you've got a patient with chronic thromboembolic disease if they've had
clots in the past or if you think that they've been having increasing clots and
their pulmonary artery pressures going up don't get the CT angio because that's
going to tell you about acute clots centrally
what you want to do is actually look at the VQ scan because it uses a nuclear
med and not contrast the GFR is not an issue so you don't have to worry about
kidney function however if there is a pneumonia then it may obscure the
ability to tell whether or not there is ventilation but no perfusion so usually
if you've got a patient with a pneumonia and a good GFR the one that you're gonna
use is a CT scan if you've got a patient with a bad GFR bad kidney function but I
just clear chest x-ray then a VQ scan is probably the one that you're gonna use
okay next ones that you can use ultrasound of the bilateral lower
extremity it's very specific what I mean by that is if you have a negative test
you cannot rule out DVT or PE if you have a positive study though you could
probably rule in both definitely rule in a DVT and also rule in a pulmonary
embolism here's the thing you ought to know about this test it is portable so
you can actually bring it to the patient if the patient's unstable in the
emergency room in the ICU you're not going to induce any risk of
taking the patient downstairs because this can come to you also in that line
is the d-dimer however it's not specific so whereas an ultrasound if it is
positive it helps you tremendously and if it is negative it doesn't help you
much at all here the opposite is the case if the d-dimer is negative it's
very helpful in telling you that there's probably no clots going on at all but if
it's positive there's a hundred and one different things that could make this
positive other than a blood clot for instance inflammation surgery things of
that nature echos are nonspecific there is the occasional sign that you'll see
where the apex may or may not be moving there's also EKG that's going to be
nonspecific you can think of an s-1 q3 t3 chest x-ray is also nonspecific you
can think of Hamptons hump or Westermarck sign again these are not
specific or sensitive but interesting and helpful to know
okay so how do you actually treat a patient whom you suspect of having a
pulmonary embolism so you're here at this point either inpatient or
outpatient and so the first thing that you're going to do is apply welles
criteria and you add it up and if it's zero to four points then it's going to
be unlikely if it's five to twelve and a half points it's good to be likely so
the next thing you do for an unlikely is check a d-dimer if the d-dimer's
negative you're good the pulmonary embolism is ruled out and by negative I
mean less than five hundred nanograms per milliliter now if it's positive then
you treat it exactly as you would if you had a likely result from the wels
criteria that we talked about before and in which case what you do is you do a CT
PA provided of course that the kidney function is good enough now if you do a
CT PA it's possible that you could miss some of those peripheral pulmonary
embolisms but the question is is are those peripheral pulmonary embolisms
significant to the point where it would be fatal if you didn't anticoagulate and
that was the question that was set out for the Christopher study so what they
did was they used this algorithm then they went and did a CT PA and if it was
positive in this case then you've ruled in the pulmonary embolism but if it was
negative they would send it and say no you've ruled out the pulmonary embolism
so what they said was is this as good as the d-dimer and his other point so what
they did was they looked at the false positive rate and they wanted to see if
we anticoagulated all these people that were positive and didn't anticoagulate
all the ones that were negative on the CT PA how did it turn out in terms of
DVT non fatal PE or fatal PE and we have those numbers right here in respective
order and you can see here that these false positive rates are pretty darn low
and this is basically what we do now in the emergency room is we look at a
patient do the Welles criteria if you've got an unlikely with a negative d-dimer
you're done if you have either and unlikely with a d-dimer that's positive
or a likely you go to see TPA if the C TPA is positive well you've made the
diagnosis if the CTA is negative well in that case you're done and
here's an example of what a CT PA looks like and you can see here that you've
got clot blocking up this entire limb of the right pulmonary artery this is the
pulmonary artery right here this is the aorta here and here you can see it
bifurcate so this goes to the right and this goes to the left and of course
you're seeing a clot in the lumen that's preventing the contrast from
illuminating you can see why a CT PA is better at detecting large central
lesions rather than peripheral lesions so here's an example of a pulmonary
embolism here's an example of a ventilation perfusion scan so there's a
gas that you inhale and it determines where in these lungs do you see any
decrease in ventilation and of course we do a technetium perfusion scan and you
can see clearly here areas that are not being perfused and these of course don't
match up with areas over here and so what you have is a mismatch in perfusion
ventilation and therefore that's a high probability for a pulmonary embolism
here's an example of a very specific finding would be very surprised if you
were to see this is a Hamptons hump and you can see here this wedge-shaped
infarct in the periphery of the lung and that is classic and very specific for a
pulmonary embolism okay well that completes this portion of
the epidemiology and diagnosis join us for the next video when we talk about
treatment
you