Lecture 20: Pulmonary Thromboembolism

Question 1

Factors leading to hypercoagulability (3 classes)

Answer 1

Hereditary risk factors, acquired risk factors (age, cancer, obesity), and triggering factors (surgery, immobilization, estrogens)

Question 2

Describe Factor V Leiden

Answer 2

Most common cause of hereditary thrombophilia; factor Va becomes resistant to action of activated proctein C; heterozygous are 3-5 fold increased risk of venous thromboembolism

Question 3

Describe prothrombin gene mutation

Answer 3

Mutation in prothrombin gene –> heterozygous are 30% increased risk of venous thromboembolism

Question 4

Three anticoagulant deficiencies

Answer 4

Protein C, protein S, antithrombin III deficiency

Question 5

Factors that lead to hypercoagulability (6)

Answer 5

Bone fractures, surgery, oral contraceptives (+ age, smoking), pregnancy (post-partum as well), foreign bodies (catheters), cancer

Question 6

Sequaelae of PE are due to what two categories…

Answer 6

1. Mechanical obstruction; 2. Mediators released from thrombus

Question 7

Two vasoconstrictive mediators released by thrombi

Answer 7

5-HT and thromboxane A2

Question 8

Three factors effecting the badness of a PE

Answer 8

1. Degree of reduction of cross-sectional area of pulmonary vascular bed; 2. Pre-existing cardiopulmonary system; 3. Consequences of hypoxic/neurohumorally mediated vasoconstriction

Question 9

Effects of obstruction

Answer 9

Normal or near-normal Pap and PVR because of recruitment and distension of pulmonary vessels; CO maintained

Question 10

Effects of obstruction >30% of pulmonary vasculature?

Answer 10

Increase in Pap and modest increase in RAP

Question 11

Effects of obstruction >50% of pulmonary vasculature…CO?

Answer 11

Cannot compensate, RAP incrases; CO drops

Question 12

In a healthy patient, what is the max mean Pap RV can generate?

Answer 12

40 mm Hg

Question 13

Gas exchange in PE: dead-space or shunt?

Answer 13

Dead-space (all V, no Q); PAO2 = air, PACO2 = 0

Question 14

PE: hyper or hypocapia?

Answer 14

Hypocapnia because of increase in total minute ventilation

Question 15

Is dead-space ventilation a cause of hypoexmia?

Answer 15

NOPE

Question 16

How does hypoxemia occur in PE? (4)

Answer 16

Increased PVR (shunt) –> this can lead to intracardiac shunt due to increased right sided pressures; decreased CO reducing venous admixture; loss of pulmonary surfactant; bronchoconstriction

Question 17

How long does it take to lose surfactant?

Answer 17

24 hours of total occlusion

Question 18

What causes bronchoconstriction in PE?

Answer 18

Platelet mediators and hypocapnia

Question 19

Is pulmonary infarction common?

Answer 19

No, because there are 3 sources of O2 to lungs (pulmonary arteries, bronchial arteries, airways)

Question 20

PE: symptoms

Answer 20

Acute onset dyspnea, pleuritic chest pain, hemoptysis, syncope

Question 21

PE: physical exam

Answer 21

Vital signs:
tachycardia, hypotension, tachypnea, hypoxemia; Lung:
may be normal OR rales (atelectasis, infarction), wheezing (bronchoconstriction), findings of pleural effusion; Cardiac:
RV heave, split S2, loud P2, systolic TR murmur, diastolic PR murmur, RV S3; Extremities:
tenderness, edema, cord (palpable clot within a vessel)

Question 22

Why could the lung exam be normal in PE?

Answer 22

It’s a VESSEL problem not a lung problem

Question 23

PE: X-ray (two named findings)

Answer 23

CAN BE COMPLETELY NORMAL; or rare findings: Hampton’s Hump (shallow wedge-shaped opacity in periphery of lung = infarction); Westmark’s sign: localized area of decreased lung vascular markings

Question 24

PE: dx

Answer 24

CT pulmonary angiography

Question 25

What is a ventilation perfusion scan? Use for PE?

Answer 25

Imaging that looks at both ventilation and perfusion; if you have decreased perfusion but OK ventilation this may suggest PE

Question 26

What imaging modality ca be used to find a DVT?

Answer 26

Lower extremity ultrasound +/- compression (no compression = clot presence)

Question 27

In PE setting, what is the value of echocardiogram (2)

Answer 27

Evaluate RV size/fxn AND assess for RV/RA thrombus

Question 28

What does D-Dimer test look for? Sensitivity? Specificity?

Answer 28

Evidence of clot formation and dissolution; sensitive and negative predictive value (i.e. if test is NORMAL then you likely DO NOT have a PE); NOT specific and poor positive predictive value

Question 29

Fate of a thrombus…

Answer 29

Grow/propagate –> fibrinolysis –> organize and recanalize

Question 30

Do most people do OK with a PE?

Answer 30

Yes, improvement (~2 months) is usually sufficient to restore normal pulmonary hemodynamics, gas exchange, and exercise tolerance

Question 31

A minority of patients will develop…WHO classification?

Answer 31

Chronic thromboembolic pulmonary hypertension; WHO IV

Question 32

PE: tx (3 catgeories)

Answer 32

Anticoagulation (heparin), thrombolysis (tPA), surgery

Question 33

What is an inferior vena cava filter?

Answer 33

Device that traps thrombi from lower extremities

Question 34

When is an inferior vena cava filter indicated? What is the risk?

Answer 34

1. Contraindicated to anticoagulant therapy; 2. Thromboembolism recurrence despite adequate anticoagulation; 3. Limited pulmonary vascular reserve; increased risk of DVT

Question 35

Does thrombolysis cause an increased bleeding risk? Therefore…

Answer 35

YES: ONLY FOR SICKEST PATIENTS