Pulmonary Embolism

hello on today's episode of intern crash

course I'm discussing pulmonary

embolisms some terms that you might

encounter when discussing Pease first

the term venous thromboembolism refers

to the presence of either a pulmonary

embolism and or a deep vein thrombosis

while the risk factors and

anticoagulation management for these two

manifestations of VTE are the same this

video will focus just on the Pease

a massive PE is one associated with

hemodynamic instability a sub massive PE

is one associated with objective

evidence of right ventricular strain

typically seen on echo but without

hemodynamic instability

there are many many risk factors for

Pease but not all are the same comparing

them is actually difficult because some

result in huge daily risk but only for a

relatively short period of time while

others have a modestly increased daily

risk but that risk is present for years

or even lifelong having said that

notable transient risk factors include

fractures of the hip or leg hip and knee

replacements major general surgery a

major trauma prolonged air flights with

a vague cutoff sometimes given up about

eight hours the presence of a central

line pregnancy and the postpartum state

and immobilization for at least three

days for any reason not already

specified more long-term risk factors

include active malignancy stroke

previous venous thromboembolism

inherited thrombophilia x' with a

magnitude of risk dependent upon the

specific genetic abnormality

antiphospholipid antibody syndrome

estrogen therapy and obesity this list

is not complete but these are the risk

factors for which their significance as

these strongest consensus

let's discuss the clinical presentation

the most common symptom and the only one

present in at least half of patients is

dyspnea the onset of dyspnea is

typically over the course of several

minutes or less but a notable minority

of patients with the PE have symptoms

that develop over hours or even days

other common symptoms occurring in

between 10 and 50 percent of patients

include pleuritic chest pain

cough wheezing hemoptysis syncope and

unilateral leg pain and/or swelling from

a concurrent DVT anecdotally the

association between PE and syncope is


with the physical exam the only sign

present and at least half of patience is

to keep Nia

other common signs include tachycardia

hypoxemia fever though the higher the

fever the more points to an alternative

diagnosis such as pneumonia or empyema

crackles decreased breath sounds

a loud pulmonary component of the second

heart sound elevated jvp and exam

evidence of a DVT such as unilateral leg

swelling edema or tenderness so what are

common findings in key diagnostic tests

ABG's can show hypoxemia with an

increased AAA gradient and respiratory

alkalosis ECGs can show sinus

tachycardia a variety of atrial

arrhythmias such as a fib and less

commonly multifocal atrial tachycardia

and T wave inversions in v1 through v4

with an incomplete white bundle branch


although the pattern of a prominent S

wave and lead one Q wave in three and

inverted T and three is considered

classic it's uncommon

chest x-rays can show a pleural effusion

and much less commonly a rounded

peripheral opacity known as Hamptons

hump and increased lucency distal to a

large vessel known as Westermarck sign

echocardiograms can show evidence of

right ventricular dysfunction such as

hypokinesia dilation and septal

flattening mcconnell sign is the

presence of akinesia of the mid free

right ventricular wall but we have

preserved apical contractility patients

with RB dysfunction can also have IVC

dilation with a lack of respiratory

variation consistent with elevated

pulmonary artery pressures

please keep in mind though despite all

these well described findings all four

of these tests can be completely normal

in a patient with a PE none of them are

sensitive enough to be used as a major

consideration in willing out the

diagnosis for example among patients

presenting to the IDI with dis Nia the

presence or absence of hypoxemia has

been found to have minimal impact on the

probability the patient has a PE and in

the case of chest x-rays in particular a

normal chest x-ray in the presence of

dyspnea is actually considered to be

suggestive of a PE so far none of what

I've discussed has been controversial

everyone agrees in general on the risk

factors for PE s and on how this

diagnosis typically presents but now now

we're going to get to the parts of the

video where some disagreements is likely

and the first is with the approach to

diagnosis if you just do a google image

search for PE diagnostic algorithm

you'll find over 100 different results

each with slightly different takes on

how to do this some place different

relative emphasis on d-dimer versus CT

versus VQ scan versus echo versus lower

extremity ultrasound some mentioned one

clinical prediction rule but not another

the diagnostic algorithm I'm going to

present here is my attempt at creating

something which is as close as to a

consensus of these different approaches

as possible with incorporation of what

supported by literature and what is

consistent to what I've observed to be

most commonly practiced here in the

United States

I will not assert that this is the one

and only way to do this having said all

that when faced with a patient who might

have in a queue PE the first step that I

do is to calculate their well score a

popular and validated clinical

prediction rule based on their score

they end up in one of three risk

categories starting with an intermediate

score of two to six the next step with

these patients is to check a d-dimer

some advocate for using an age adjusted

arrange for patients above the age of 50

if the d-dimer is normal for patients in

this intermediate category a PE has been

ruled out

if the d-dimer is elevated the next step

is a CT pulmonary angiogram or either a

VQ scan or bilateral lower extremity

duplex ultrasound

if significant renal disease or prior

anaphylactic reaction to contrast

precludes CT contrast administration

pregnancy would be another consideration

here if the patient's well score is zero

or one putting them into the lowest risk

category the next step would be to apply

the perc rule which asks if any of eight

features are present all of which would

increase the risk of PE if none of the

perk features are present in the patient

who also has a low well score a PE has

been ruled out without any additional

diagnostic tests on the other hand if

the well score is greater than six that

puts the patient into the highest risk

category in which case a normal day

dimer would not sufficiently decrease

the probability of PE to consider it

ruled out therefore these patients

should offer C directly to C TPA or one

of the aforementioned alternatives C TPA

is an unusually sensitive test so if it

does not show a PE a PE has been ruled

out for the overwhelming majority of

patients if it does show PE then

obviously it's been ruled in but if it's

inconclusive for some reason then you're

stuck doing another test if the patient

appears to have minimal other lung

disease a VQ scan is probably the best

option but for the patient with chronic

lung disease BQ scans are frequently

non-diagnostic as well so bilateral leg

duplex ultrasounds may be best there are

a ton of additional caveats with this

algorithm first if the patient is to

hemodynamically unstable to safely go to

the CT scanner consider getting a

bedside echo first and even making a

presumptive diagnosis of PE if there is

a high well score combined with evidence

of acute RV dysfunction if there are

physical exam science of a DVT I'd skip

the d-dimer and see TPA altogether and

just go with an ultrasound

since the treatment of a clinically mild

PE and the DBT are more or less the same

if the patient has a high well score and

a negative C TPA if the post-test

probability of a PE still feels too high

to rule out the diagnosis one can

consider following it with a VQ or

ultrasound there's a common variation to

the well score in which patients are

placed into one of two categories rather

than one of three algorithms which use

this approach tend to not incorporate

the perc rule at all and thus require

all patients to receive either a d-dimer

or C TPA lastly there is an alternative

to the well score called the Geneva

score but which I haven't personally

seen used

next up is how to tree Pease and I'll

tackle this in two parts first a

treatment algorithm for hemodynamically

stable patients the first question to

ask his anticoagulation contraindicated

an incomplete list of contraindications

includes active bleeding major trauma

recent or planned high-risk procedure

severe bleeding disorders such as

haemophilia and may or may not include

intracranial tumors partly depending on

the tumor type if there is a

contraindication then the patient should

probably receive an IVC filter now I'm

not a fan of filters in general but

there is relatively strong expert

consensus with this specific situation

if anticoagulation is not

contraindicated you should initiate

anticoagulation but which one to choose

in most patients apixaban or rivaroxaban

are the best choices the doxa ban and

dabigatran are also approved in the US

for treatment of p/es

but based on available data it's

recommended that they be overlapped with

a parental anticoagulants for this

particular indication and these drugs

offer no significant benefits over a

PICC Seban and rivaroxaban so i use them

in patients with cancer low molecular

weight heparin is believed to be more

effective than alternatives and in

pregnant patients low molecular weight

heparin is believed to be the safest


for patients with a cracking clearance

less than 30 the only conventional

option is warfarin overlapped with an

unfractionated heparin bridge and in

patients with an anticipated upcoming

procedure in the immediate future

place them on unfractionated heparin and

then convert them to any Dilek


regardless of which anticoagulant you

choose it should be continued for at

least three months at which point a

discussion between doctor and patient

should determine if the risk benefit

ratio favors stopping at that time

versus extending it to six months and

reassessing again or extending



next is the treatment of human

dynamically unstable patients first

consider human dynamic support while

fluids are a mainstay of shock treatment

with massive PE in which the RV is

already pressure overloaded and

overstretched excessive fluid can be


so fluid is given it should be a very

modest in volume vasopressors may be

necessary but there is no consensus on

which one should be first-line

with respiratory support non-invasive

positive pressure is rarely if ever

helpful unfortunately intubation is not

much better and should be delayed as

long as possible

largely because patients with massive PE

are at a particularly high risk of

cardiac arrest with intubation and

mechanical ventilation due in part to an

abrupt drop in their RV preload keep in

mind that patients with massive PE are

more likely to die from cardiovascular

collapse than they are from respiratory

failure therefore the most important

goal in massive PE is to restore

pulmonary blood flow so ask if

thrombolysis is contraindicated there's

a lot of overlap with anticoagulation


but thrombolysis carries greater risk of

harm so the contraindications are

greater in number and broader for

example any intracranial tumor is

generally considered to be a

contraindication recent ischemic stroke

and the history of prior intracranial

hemorrhage there are others if not

contraindicated give it and if the

patient is truly crashing and arrest

seems imminent to some extent all

contraindications become relative half

those thrombolysis is an option to

consider in such cases as well if there

is sufficient improvement in

hemodynamics after thrombolysis that's

great next you want to initiate or

reinitiate infusion of unfractionated

heparin after checking stat coax some

clinicians will consider placing an IVC

filter for patients whose

cardiopulmonary reserve is felt to be

poor enough then another PE will likely

be fatal but there's no consensus here

now what do you do for the patient who

does have an absolute contraindication

to thrombolytics

or who has insufficient improvement

following thrombolysis these patients

need something called an embolectomy in

which the PE is physically removed from

the pulmonary artery this can either be

done via surgical or a catheter based

approach of which there are several

which will be options for your patient

is totally institution dependent if the

patient is crashing and clinical

suspicion for a PE is high empiric

anticoagulation and/or thrombolysis

should be considered before it's been

fully ruled in if a definitive diagnosis

cannot be made in a timely manner lastly

with treatment ECMO and inhaled

pulmonary vasodilator z' may also have a

role in the crashing patient with

massive PE in hospitals where these are


a lot has been written about

prognostication following acute Pease

some key markers were having a poor

short-term outcome include the presence

of shock RV dysfunction and elevated

troponin and a concurrent DVT presumably

but since it means there is more

thrombus left potentially embolize in

addition to these negative prognostic

markers that are examined in isolation

there is also a commonly used clinical

prediction tool called the pulmonary

embolism severity index this assigns

points to a variety of features related

to the person's demographics history and

physical exam the total number of points

then results in the assignment to one of

five categories of risk for 30-day

mortality the lowest risk category has a

30-day mortality of 0 to 1.6 percent

while the highest risk category has a

30-day mortality of 10 to 24 percent the

PD severity index is not without critics

in my opinion the most notable criticism

is that it places a large emphasis on

the patient's age and relatively low

emphasis on signs of acute physiologic

compromise so an elderly person with

dementia and history of cancer will have

an unusually high score

even with a trivially small PE it's kind

of like the difference between

considering the 30-day overall mortality

which this does rather than the 30-day

PE specific mortality which may be more

relevant for some treatment and triage

decisions speaking of triage decisions

one that frequently comes up is whether

a patient with a small PE diagnosed in

the emergency room can be safely

discharged directly to home without an

admission in my opinion one can consider

outpatient treatment of a PE if all of

the following are presents the patient

has a PE severity index class of one to

two normal vitals no major risk factors

for bleeding with initiation of

anticoagulation normal mental status

no concurrence DVT they must have

adequate symptom control

and good home support overall most

patients will not meet all these

criteria and thus should be admitted

just a few final considerations the

radiographic size of a PE does not

correlate well with symptoms a person's

cardiopulmonary reserve is also a major

contributing factor to the extent of

clinical manifestations a significant

number of PE s are asymptomatic it's

unknown which of these should be treated

avoid unnecessary lines in patients

undergoing or who might undergo

thrombolysis and finally while it was

common practice in the past most

patients with a first unprovoked PE

should not receive a so-called hyper

quag workup the presence of an inherited

thrombophilia typically has little

impact on treatment decisions since it's

generally recommended that patients with

a single unprovoked PE and low to

average bleeding risk should be on

indefinite anticoagulation anyway

however they should undergo

age-appropriate cancer screening