SM 169 Pulmonary Embolism

Question 1

What is the classic presentation for Pulmonary Embolism?

Answer 1

There isn’t one; though typical symptoms can include pleuritic chest pain, hemoptysis, and dyspnea

Question 2

Why is treating Pulmonary Embolism difficult?

Answer 2

It produces non-specific symptoms, has high morbidity and mortality if missed, but also lends itself towards over-testing and over-treatment

Question 3

What are the 3 risk factors that fuel Pulmonary Embolism?

Answer 3

Venous stasis, alterations in coagulation, and vascular injury

Question 4

How does venous stasis promote Pulmonary Embolism?

Answer 4

Immobility from lying in a bed, prolonged ravel, or paralysis can promote clot formation in the legs that dislodges and blocks the Pulmonary circulation

Question 5

How do alterations in coagulation promote Pulmonary Embolism?

Answer 5

Hereditary thrombophilias (Factor V), estrogen therapy, and malignancy can predispose clot formation which can block the Pulmonary circulation

Question 6

How does vascular injury promote Pulmonary Embolism?

Answer 6

Surgery, trauma, and childbirth can all injure the vasculature and promote the formation of clots that dislodge and block the Pulmonary circulation

Question 7

How are the risk factors for Pulmonary Embolism “synergistic”?

Answer 7

The risk factors make eachother worse and increase the likelihood of Pulmonary Embolism

Question 8

Where do most Pulmonary Embolism arise from?

Answer 8

Deep veins in a proximal lower extremity, such as the Femoral and Popliteal veins, which then break off and block the Pulmonary circulation

Question 9

What is a Pulmonary Embolism from a deep vein called?

Answer 9

DVT, most common type

Question 10

What predisposes upper extremity DVT’s?

Answer 10

The use of Peripherally Inserted Central Catheters (PICC’s)

Question 11

Where are the possible areas for a Pulmonary Embolism to cut off circulation?

Answer 11

"Saddle" = at the intersection of the RPA and LPA
"Segmental" = blocking a major Bronchi
"Sub-segmental" = blocking a distal branch of Pulmonary Circulation

Question 12

What type of Hypoxemia results from blocking a Pulmonary Artery?

Answer 12

Dead Space

Question 13

What type of Hypoxemia results from a Pulmonary Embolism?

Answer 13

V/Q Mismatch

Question 14

What does a sudden increase in dead space indicate in a patient?

Answer 14

Pulmonary Embolism, due to sudden loss of perfusion to an area of the lung

Question 15

Does a Pulmonary Embolism result in hypercapnia or hypocapnia?

Answer 15

Pulmonary Embolism results in Hypocapnia, because the loss of blood flow triggers an increase in ventilation to maintain PaO2 leading to decreased PaCO2

Question 16

Why does Pulmonary Embolism result in hypoxemia?

Answer 16

The blood that is cut off by the embolism is shunted to other areas that are not blocked, leading to an increase in flow that overwhelms regional ventilation, precipitating V/Q mismatch

Question 17

How does Pulmonary Embolism lead to CV collapse?

Answer 17

A large Pulmonary Embolism increases afterload on the RV, leading to RV dilation and a shift of the IV Septum into the LV, compressing the LV and lowering LV Preload leading to lower Cardiac Output

Question 18

How is hypotension in the setting of Pulmonary Embolism treated differently?

Answer 18

Normally, acute hypotension is treated by administering fluids; however, in Pulmonary Embolism induced RV failure, pushing fluids increases the strain on the RV by increasing it’s preload, leading to more dilation and worsening Cardiac Output

Question 19

What sign indicates a Pulmonary Embolism on an echo of the heart?

Answer 19

The “D” sign - due to RV compression of LV

Question 20

How does Pulmonary Embolism effect the RV?

Answer 20

Vicious cycle; Increased afterload leads to dilation, but dilation causes LV preload to drop and diminishes CO, leading to further dilation. Additionally, increased RV pressure leads to decreased coronary perfusion, in the setting of increased myocardial O2 demand

Question 21

Why can Pulmonary Embolism rapidly decompensate?

Answer 21

Increased O2 demand by the heart is not met, and actually worsened, by the failing Cardiac Output due to RV dilation and decreased LV Preload

Question 22

What’s the point of a CXR in a suspected Pulmonary Embolism if it can’t be seen?

Answer 22

CXR can be sued to identify alternative diagnoses and rule out other things, allowing diagnosis of Pulmonary Embolism by exclusion

Question 23

What results from a CXR would raise suspicion for Pulmonary Embolism?

Answer 23

Normal CXR with respiratory symptom should raise concern for Pulmonary Embolism

Question 24

Why is angiography no longer the gold standard for diagnosis of Pulmonary Embolism?

Answer 24

Angiography is invasive, requires contrast, specialist involvement, and cannot detect small clots

Question 25

What is the gold standard for diagnosis of DVT?

Answer 25

Compression ultrasound

Question 26

How does a compression ultrasound work?

Answer 26

Use an ultrasound to find a major vein, and compress the patient to see the vein close on the ultrasound; if the vein doesn't close, a clot is present

Question 27

Does a negative lower extremity ultrasound exclude DVT?

Answer 27

No, it just says there's no clot in the vein on the ultrasound, and the clot may have already migrated elsewhere

Question 28

How is Type IV Pulmonary Hypertension diagnosed?

Answer 28

V/Q scan

Question 29

How does a V/Q scan work?

Answer 29

Inject and inhale radiolabeled isotopes to look for V/Q defects without contrast

Question 30

What are the limits of a V/Q Scan?

Answer 30

Doesn't work well on patients with chronic lung disease

Question 31

Why does a V/Q scan detect Pulmonary Embolism?

Answer 31

Pulmonary Embolism results in increased flow through regions without the embolism and absent flow in the blocked region, causing a V/Q mismatch

Question 32

What is the best test for Pulmonary Embolism?

Answer 32

PE-CT

Question 33

How does a PE-CT scan work?

Answer 33

A bolus of contrast is inserted into the Pulmonary circulation, which should spread through the vasculature if unobstructed by Pulmonary Embolism

Question 34

What are the pro's of PE-CT?

Answer 34

Fast, widely available, and high diagnostic accuracy

Question 35

What are the con's of PE-CT?

Answer 35

Radiation, contrast, and less accurate for sub-segmental thrombi

Question 36

What are the test characteristics of the D-dimer?

Answer 36

High sensitivity but low specificity

Question 37

Is a D-dimer a rule out or a rule in test?

Answer 37

Rule's out Pulmonary Embolism due to high sensitivity and NPV, but can't rule in due to low specificity and low PPV

Question 38

How does a D-dimer work?

Answer 38

Measures a fibrin degradation product which is present after a clot or embolism forms

Question 39

What makes for an ideal diagnostic algorithm?

Answer 39

Low miss rate and avoids expensive tests

Question 40

What is a Wells Score?

Answer 40

Uses subjective and objective criteria to score a patient's risk for PE; Well's > 4 = PE likely

Question 41

What is the cutoff on a Wells Score?

Answer 41

Score > 4 makes PE likely, Score =< 3 makes PE unlikely

Question 42

What does the Wells Score do, statistically?

Answer 42

Sets pre-test probability

Question 43

What was the Christopher study?

Answer 43

Investigated the use of Wells Score + D-dimer to predict Pulmonary Embolism; extremely successful algorithm

Question 44

What was the Christopher study algorithm to predict Pulmonary Embolism?

Answer 44

``` In a suspected PE, first calculate Well Score If Well Score > 4, PE likely, do CT-PA If Well Score =< 3, D-dimer test If D-dimer elevated, PE likely, run CTPA If D-dimer low, PE unlikely ```

Question 45

Why is a Well Score > 4 sufficient to initiate CTPA?

Answer 45

Because a Well Score > 4 has a high pretest probability of Pulmonary Embolism

Question 46

What are the acute treatment options for Pulmonary Embolism?

Answer 46

Heparin or Systemic Fibrinolytic Therapy, depending on severity

Question 47

What sets the treatment used for Pulmonary Embolism?

Answer 47

Severity of Pulmonary Embolism; for most patients, Heparin or LMWH are acceptable, but for PE + Shock/Cardiac Arrest, use a Systemic Fibrinolytic

Question 48

How does Heparin treat Pulmonary Embolism?

Answer 48

Infused via IV to help prevent clot formation, but requires lab monitoring

Question 49

How do LMWH's treat Pulmonary Embolism?

Answer 49

SubQ injections that do not require lab monitoring help prevent clot formation

Question 50

How is Pulmonary Embolism in the setting of shock or cardiac arrest managed?

Answer 50

Use a systemic fibrinolytic to immediately break of the embolism and restore cardiac output

Question 51

What are the risks of systemic fibrinolytic therapy?

Answer 51

Higher risk for internal bleeding, including intracranial hemorrhage

Question 52

How should treatment of PE begin in the setting of high pre-test probability for PE?

Answer 52

Start anticoagulants while you evaluate

Question 53

What is the treatment for PE if anti-coagulants are contraindicated?

Answer 53

Insert an IVC filter to catch emboli before they reach the heart

Question 54

What is Submassive Pulmonary Embolism and how is it treated?

Answer 54

Pulmonary Embolism with RV dysfunction but without shock or cardiac arrest, treated with anticoagulants

Question 55

What are the treatment options for chronic Pulmonary Embolism?

Answer 55

Vitamin K antagonists (Warfarin) LMWH (Enoxaparin) Novel Oral Anticoagulants (RABE)

Question 56

What are the pro's and con's of Warfarin?

Answer 56

``` Pro's = low cost, reversible, safe in renal disease Con's = life long blood monitoring ```

Question 57

What are the pro's and con's of LMWH?

Answer 57

``` Pro's = no lab monitoring Con's = harder to reverse, hard to use in renal failure ```

Question 58

What are the pro's and con's of Direct Oral Anticoagulants?

Answer 58

Pro's = no lab monitoring | Con's expensive, limited reversal agents

Question 59

What are the 3 types of chronic Pulmonary Embolism?

Answer 59

Provoked, unprovoked, and Associated w/ Malignancy

Question 60

How is Provoked Pulmonary Embolism treated?

Answer 60

3 months of therapy

Question 61

How is Unprovoked Pulmonary Embolism treated?

Answer 61

3 months of therapy at a minimum, possibly indefinite depending on bleeding risk

Question 62

How is Pulmonary Embolism associated with Malignancy treated?

Answer 62

3 months minimum, until cancer is treated