Pulmonary Embolism

Question 1

What is a venous thromboembolism

Answer 1

either a pulmonary or deep vein thrombosis

Question 2

Define submassive PE

Answer 2

A PE associated with evidence of right ventricular dysfunction and/or biomarkers of myocardial injury without systemic hypotension (systolic blood pressure < 90 mmHg).

Question 3

Define massive PE

Answer 3

A PE associated with persistent systemic hypotension (systolic blood pressure < 90 mmHg) or hemodynamic collapse

Question 4

What is Virchows triad?

Answer 4

The pathophysiologic factors contributing to development of PE:

1. Vascular injury
2. Coagulation alteration
3. Venous stasis

Question 5

• Immobility (paralysis, prolonged travel, critical illness)
• Casting
• Congestive heart failure
• Obesity
• Age > 60
These are all risk factors for what aspect of Virchow’s triad?

Answer 5

venous stasis

Question 6

• Hereditary thrombophilias
• Heparin-induced thrombocytopenia
• Antiphospholipid antibody syndrome
• Nephrotic syndrome (loss of anti-thrombin III)
• Estrogen therapy
• Malignancy
These are all risk factors for what aspect of Virchow’s triad?

Answer 6

altered coagulation

Question 7

•	Surgery
•	Trauma
•	Post-partum
•	Indwelling vascular access
•	History of VTE
These are all risk factors for what aspect of Virchow's triad?

Answer 7

vascular injury

Question 8

What are the 3 most common hereditary thrombophilias?

Answer 8

The three most common hereditary thrombophilias are factor V Leiden deficiency (the most common), prothrombin G20210A, and hyperhomocysteinemia.

Question 9

When is screening for hereditary thrombophilias such as factor V leiden defciency recommended?

Answer 9

a strong family history of VTE
an unprovoked VTE at a young age
recurrent VTE in the absence of other risk factors
thrombosis at an unusual vascular site (i.e., not a deep vein in the leg or upper extremities)

Question 10

What is the most common cause of a PE? (be specific)

Answer 10

proximal lower extremity DVT

Question 11

Why are upper extremity DVT’s an increasingly common cause of PE?

Answer 11

increased use of PICC lines

Question 12

How do you define a proximal lower extremity DVT?

Answer 12

above the knee

Question 13

What is a saddle PE?

Answer 13

When thrombus lodges in the main pulmonary artery trunk

Question 14

How does the body compensate for the dead space created by a PE?

Answer 14

Most patients are able to respond to this increased dead space by increasing minute ventilation and often hyperventilating so that an elevated PaCO2 is an uncommon finding in PE. However, in patients unable to augment minute ventilation (e.g., deeply sedated patients on a ventilator), a sudden increase in PaCO2 that occurs absent a change in minute ventilation may signal the development of a VTE.

Question 15

What is the main cause of hypoxemia in patients with PE

Answer 15

dysregulated V/Q matching

Question 16

In patients with a massive PE, what contributes to hypoxemia?

Answer 16

decreased mixed venous oxyhemoglobin saturation

Question 17

What causes death in PE, usually?

Answer 17

cardiovascular collapse

Question 18

How can relatively healthy patients with a PE maintain CO?

Answer 18

recruitment of pulmonary vessels and increased right ventricular (RV) stroke volume even when 40% of their pulmonary vasculature is obstructed.

In patients with limited CV reserve or when vascular obstruction exceeds 50%, shock and hemodynamic collapse rapidly develop through 2 major pathways.

Question 19

At what point does vascular obstruction prevent compensation of CO in health patients?

Answer 19

when obstruction is > 50%

Question 20

How does a PE affect the heart acutely?

Answer 20

increases RV afterload, which leads to fatigue and dilation

Question 21

How is CO affected in a PE by RV afterload increases?

Answer 21

RV dilation pushes the septum to the side, which impacts LV preload and decreases CO

Question 22

Why is the drop in CO a problem during a PE?

Answer 22

it worsens the O2 mismatch in the RV, leading to ischemia, progressive dilation and eventually cardiac arrest

Question 23

What is a chest xray good for in working someone up for a PE?

Answer 23

identifying other causes of symptoms (i.e. ruling in, not out)
a normal CXR should RAISE suspicion of a PE!!!

Question 24

Why are pulmonary and venography angiography not ideal, despite being the previous gold standard for PE?

Answer 24

these exams are invasive (they require intravenous cannulation of a proximal deep vein), require specialized expertise to perform, are subject to significant interrater reliability especially for smaller thrombi, and require injection of intravenous contrast putting patients at risk for allergic reactions and kidney injury.

venography has been replaced with ultrasound

Question 25

Does lower extremity ultrasound have good or bad sensitivity for PE?

Answer 25

poor sensitivity - it is good for above the knee DVT in the setting of PE, but not good for PE in isolation

Question 26

In theory, what should a PE do to the V/Q mismatch scan results?

Answer 26

a PE should produce mismatched segmental-sized ventilation and perfusion defects.

However, 80% of scans are non specific

Question 27

What is the most frequent diagnostic scan for a PE?

Answer 27

the PE-CT/CTPA

Question 28

What are two drawbacks of the CTPA?

Answer 28

A CTPA does require exposure to ionizing radiation which is especially a concern for younger and/or pregnant patients and requires intravenous contrast which (as with invasive angiography) puts patients at risk for allergic reactions and kidney injury.

Question 29

What should diagnostic testing for a suspected VTE be guided by?

Answer 29

an assessment of the patients pre test probability!!

i.e. validated risk score

Question 30

What is a PE likely Wells score?

Answer 30

> 4

Question 31

What is a PE unlikely Wells score?

Answer 31

< 4

Question 32

What does a D dimer assay measure?

Answer 32

product of fibrin degradation

Question 33

Are D dimer assays sensitive or specific for VTEs?

Answer 33

sensitive (good screen) but not specific - they are used to rule out a PE but not to rule in

Question 34

What can cause an elevated D dimer? what is the level? What does this mean for assessment of VTE?

Answer 34

advanced age, inflammation, trauma, pregnancy, malignancy, VTE

> 500

Does not rule-in PE, only a low level can rule out VTE

Question 35

If someone has a Wells score of less than 4, what should you do next to evaluated for VTE?

Answer 35

D dimer testing

Question 36

If someone has a Wells score over 4, what should you do next to evaluate for a VTE?

Answer 36

CTPA

Question 37

What are the two options for acute VTE therapy?

Answer 37

1. An infusion of unfractionated heparin (UFH). Dosing typically follows a weight-based dosing nomogram with an 80 U/kg bolus followed by an 18 U/kg/hour infusion. Activated partial thromboplastin times (aPTTs) are monitored every 6 hours to ensure sufficient and safe levels of anticoagulation.
2. Subcutaneous injections of low-molecular-weight heparin (LMWH). Examples include enoxaparin or dalteparin.

Question 38

How do you monitor unfractionated heparin anticoagulation in a VTE patient?

Answer 38

aPTT’s every 6 hours

Question 39

What are drawbacks to the use of LMWH in acute VTE therapy?

Answer 39

1. dosing can be difficult in patients at the extremes of body weight and in those with renal insufficiency. In these scenarios, monitoring anti-Xa levels is usually required. 2. LMWHs are not as immediately reversible as UFH which has a readily available antidote – protamine. This can be problematic in cases of severe bleeding.

Question 40

When should you start anticoagulant therapy in a patient with a high pre test probability of PE?

Answer 40

immediately, while waiting for diagnostic testing

Question 41

If someone has an absolute contraindication to anticoagulation (i.e. active bleeding) what should you do in the treatment of a PE?

Answer 41

Placement of an inferior vena cava filter to prevent further embolization

Question 42

In patients with a persistent systemic hypotension, hemodynamic collapse, and a PE (massive), what is indicated as treatment?

Answer 42

systemic fibrinolytic therapy

Question 43

Does the term “massive PE” refer to the size of the thrombus, the degree of hemodynamic collapse, or both?

Answer 43

only to hemodynamic alterations

Question 44

What does the American college of chest physicians recommend for the treatment of submassive PE?

Answer 44

The American College of Chest Physicians (ACCP) recommends against routine use of systemic fibrinolytic therapy for patients with submassive PE. Patients with submassive PE (especially those with multiple high-risk features) are best managed as part of a multidisciplinary PE team (as is done here at Northwestern).

Question 45

What is the most common long term therapy for VTE?

Answer 45

Vitamin K antagonists (VKAs): VKAs (most commonly warfarin) remain one of the most common anticoagulants used for the treatment of VTE. Advantages includes their low cost, reversibility, and safety in patients with renal impairment. The major disadvantage is the need for life-long periodic laboratory monitoring to ensure safe and sufficient levels of anticoagulation.

Question 46

What is the preferred long term therapy for cancer associated VTE?

Answer 46

LMWH

Question 47

What does the ACCP recommend for long term therapy of non-cancer associated VTE? What are the cons of this?

Answer 47

novel oral anticoagluants like apixaban or edoxaban, NOT warfarin.

Advantages include their rapid onset and predictable pharmacokinetic profiles (obviating the need for laboratory monitoring). Disadvantages include cost, variable insurance coverage, and limited or no options for immediate drug reversal in the setting of bleeding.

Question 48

What is the minimum length of long term therapy for a VTE, regardless of the type?

Answer 48

3 months

Question 49

If a patient has an unprovoked VTE and low to moderate bleeding risk how long should anticoagulant long term therapy be continued?

Answer 49

3 months - infinity

Question 50

What is the most severe complication of a PE?

Answer 50

the development of chronic thromboembolic pulmonary hypertension (CTEPH) which occurs in ≈ 1-4% of patients with a PE.

Question 51

When is anticoagulant prophylaxis recommended in the setting of increased VTE risk?

Answer 51

For patients with at least one risk factor for VTE, prophylactic doses of anticoagulantion are recommended to help prevent the development of VTE. Options include subcutaneous heparin and LMWH. The intensity of dosing is adjusted based on a patient’s risk profile. For patients with a contraindication to pharmacologic thromboprophylaxis, intermittent pneumatic calf compression devices are recommended.

Question 52

A 65-year-old male with stage IIIB lung adenocarcinoma presents to the emergency department with pleuritic chest pain and shortness of breath. He undergoes computed tomography pulmonary angiography and is found to have an acute PE in a segmental branch of his right pulmonary artery. He is started on an infusion of unfractionated heparin (UFH) and transferred to an inpatient medicine floor as he is hemodynamically stable without evidence of right heart strain or myocardial injury. He tolerates anticoagulation without complication and has no clear contraindications to long-term therapy. Your team begins planning for discharge in the coming days. Which anticoagulation regimen would you recommend?

a. Warfarin (a vitamin K antagonist) for 6 months
b. Enoxaparin (a low-molecular-weight heparin) for 3 months
c. Warfarin for 3 months followed by consideration of an inferior vena cava filter given his risk profile.
d. Extended-duration (12 months or greater) of enoxaparin

Answer 52

D. This patient has a malignancy-associated PE without clear contraindications to anticoagulation or a high risk of bleeding. The ACCP recommends LMWH over VKA therapy for patients with malignancy-associated VTE. For patients with active cancer, consideration should be given to extending anticoagulation indefinitely if the patient is not at high risk of bleeding.

Question 53

A 75-year-old female presents to urgent care clinic with dyspnea. She has a history of a provoked right femoral DVT 10 years ago treated following a cholecystectomy for which she was treated with 3 months of warfarin. Her heart rate is 110 and she is tachypneic but her blood pressure is normal. A basic metabolic panel and complete blood count are unrevealing. What is the most appropriate next step?

a. Obtain a D-dimer level
b. Obtain a CTPA
c. Administer systemic fibrinolytic therapy
d. Administer unfractionated heparin before pursuing additional testing

Answer 53

D. This patient has a Wells score of 6 and is at very high risk of having a PE. In patients with a very high pre-test probability of having a PE, anticoagulation therapy should be promptly initiated while pursuing additional testing as long as there are no clear contraindications to anticoagulation.

Question 54

What are the major disadvantages of computed tomography pulmonary angiography?

Answer 54

Major disadvantages of CTPA include exposure to ionization radiation, risk of allergic reaction and/or kidney injury with intravenous contrast administration, and low interrater reliability for small sub-segmental thrombi.