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IPFC 3 Midterm 2 > VTE Pathophysiology > Flashcards

VTE Pathophysiology Flashcards

1
Q

What are the 3 functions of endothelium layer that lines blood vessels

A
  1. Barrier: hides subendothelial components that activate clotting cascade
  2. Antiplatelet/antithrombotic secretions: to inhibit platelets/clotting cascade
  3. Fibronolytic sectrions: to break down any clots that do end up forming
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2
Q

What occurs in primary hemostasis during a cut?

A
  • Collagen and vWF factor are exposed to blood
  • Interacts with GP Ia and GP Ib to stop blood
  • Platelet secretes ADP, TXA2, 5-HT
  • This activates GP IIb/IIIa in other platelets to form plugs
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3
Q

What occurs in secondary hemostasis during a cut? What is the role of thrombin? (2)

A

Tissue factor is responsible for triggering the extrinsic pathway
- initiates coagulation cascade

Prothrombin -> Thrombin which further activates + recruits platelets to site of injury (2 outcomes):
1. Accelerates production of more thrombin
2. Converts fibrinogen to fibrin to make clot more stable

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4
Q

Does primary and secondary hemostasis happen at the same time?

A

Yes

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5
Q

What are the roles of activators and inhibitors of the clotting process? Give examples of each

A

Activators: make platelet plug bigger/stronger
- vWF
- Tissue factor
- Factor 7a, 10a, 12a
- Thrombin
- Factor 13a

Inhibitors: Limit size of platelet plugs
- Heparan
- Thrombomodulin
- Antithrombin
- Protein C, S

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6
Q

Define thrombosis

A

Process that occurs with inappropriate, or over-activation of hemostasis in an uninjured or slightly injured blood vessel
- results in a thrombus (blood clot)

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7
Q

Define arterial thrombi. Give examples

A

Ruptured atherosclerotic plaques in arteries
- MI
- stroke
- peripheral artery disease

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8
Q

Define venous thrombi. Give examples

A

stasis of blood flow in a DAMAGED VEIN (after surgery or trauma)
- DVT
- PE

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9
Q

Define embolism

A

An object migrates from one part of the body to cause a blockage of a blood vessel in another part of the body

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10
Q

Which injury in the leg gives the higher risk of thrombus embolization? Give examples

A

Proximal deep veins
- All iliac veins
- All femoral veins
- Saphenous vein
- Popliteal vein

Always require treatment

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11
Q

Which injury in the leg gives the lower risk of thrombus embolization? Why?

A

Distal deep veins
and superficial veins

Further away from lungs

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12
Q

T/F VTE is the most common CV disorder in canada

A

False
2nd most common

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13
Q

What are the % of people with DVT getting symptomatic PE, PTS, or recurrent DVT or PE in the next 10 years

A

All 1/3

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14
Q

What is the % of patients with VTE who have no identifiable risk factors

A

50%

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15
Q

What is the in the virchow’s triad?

A
  • Vessel wall injury
  • Stasis of blood flow
  • Hypercoagulability

Most patients have at least 1. The more, the greater the risk

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16
Q

Define vessel wall injury in the triad

A

this exposes subendothelial factors (C and vWF to circulating blood), beginning primary and secondary hemostasis
- Increased risk of over-coagulation

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17
Q

Define stasis of blood flow in the triad. Which type of blood flow is at an increase risk of coagulation

A

Thrombotic blood flow (inc risk, sedentary time)
- slow rate
- turbulent

Antithrombotic blood flow
- fast rate
- laminar flow

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18
Q

What can cause hypercoagulability (inc coagulability)

A
  • Protein C or S difficiency (inhibitors of coagulation cascade)
  • Prothrombin gene mutation
  • Antiphospholipid antibodies
  • Antithrombin deficiency
  • Factor V Leiden
  • Pregnancy
  • Estrogen therapy
  • Malignancy (cancer)
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19
Q

What are the highest risk factors for VTE

A
  • Fracture (hip or leg)
  • Hip or knee replacement
  • Major general surgery
  • Major trauma
  • Spinal cord injury
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20
Q

What are the moderate risk factors for VTE

A
  • Arthroscopic knee surgery
  • central venous lines
  • Chemotherapy
  • Heart or resp failure
  • Hormone replacement
  • Malignancy (cancer)
  • COCs
  • Paralytic stroke
  • pregnancy POSTPARTUM
  • Previous VTE
  • thrombophilia
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21
Q

What are the low risk factors for VTE

A
  • Bed rest 3 days
  • Immobile due to sitting (car, plane)
  • Increasing age
  • laparoscopic surgery
  • obesity
  • pregnancy (during)
  • varicose veins
22
Q

DVT presentation
Symptoms
Signs
Labs

A

Symptoms
- UNIlateral swelling/warmth (one leg)
- erythema (redness)
- localized pain/tenderness

Signs
- dilated superficial veins
- palpable cord

Labs
- elevation of D-dimer (breakdown product of fibrin clots)
- high erythrocyte sedimentation rate
- high WBC

23
Q

PE presentation
Symptoms
Signs
Labs

A

Symptoms
- cough
- hemoptysis (coughing blood)
- chest pain/tightness
- SOB
- dizziness/lightheadedness
- palpitations

Signs
- tachypnea (high breathing rate)
- tachycardia
- diaphoresis (high sweating)
- hypoxemia (low O2 in blood)
- fever
- distended neck veins
- ECG changes

Labs (similar to DVT)
- elevation of D-dimer (breakdown product of fibrin clots)
- high erythrocyte sedimentation rate
- high WBC

24
Q

What is the scoring system for VTE diagnosis called?

A

Well’s cirteria

25
Q

Explain the D-dimer test
What is good for?
Describe its sensitivity & specificity

A

Sensitivity: VERY sensitive
- everyone with VTE will have an elevated d-dimer

Specificity: not specific, people with VTE can still have an elevated d-dimer

SNOUT: negative = good for ruling out VTE

If positive –> check with another test

26
Q

Describe the compression ultrasonography test ?
How to tell if there is a thrombus?

A
  1. Ultrasound transducer is applied to leg in femoral artery and popliteal artery (behind knee)
    and pressure is applied to leg

If thrombus present the vein will NOT collapse
- Healthy veins collapse easily
- arteries have ticker walls and do not collapse with light pressure

27
Q

What is the most common diagnosis for PE

A

Spiral computed tomography (CT scan)

28
Q

Explain the ventilation/perfusion V/Q scan

A

lower dose of radioactive dye is injected (perfusion) and inhaled (ventilation), machine compares the images of both
- mismatch in perfusion/ventilation may indicate PE
- useful for pregnant women (lower dose of radioactive dye)

29
Q

What percent of distal DVT extend above the knee?

A

25%
1/4

30
Q

When do we treat Distal DVT

A

if they are symptomatic

31
Q

Where do most symptomatic DVTs start?
when do they often become symptoamtic

A

most symptomatic DVTs start below the knee
they often become symptomatic when they extend past the knee

32
Q

WITHOUT treatment, what is the % of patients with symptomatic proximal DVT that will develop PE in 3 months

A

50%

33
Q

What % of patients get post-thrombotic syndrome complication of DVT

A

20-50%

34
Q

What is the etiology of PTS

A

Due to an residual thrombus or vessel damage from the first clot
- Since anticoagulation therapy doesn’t lyse the original thrombus, only prevents extension/embolization

35
Q

What are symptoms of PTS?

A
  • pain
  • heaviness
  • swelling
  • cramps
  • itching/tingling of limb
    (can be persistent or intermittent)
36
Q

What is the treatment of PTS?

A

No good treatments, best to PREVENT DVT
- elastic compression stockings may help a bit with symptoms

37
Q

What is the annual risk of recurrent VTE in the first year after stopping treatment if:
transient, reversible risk factor (surgery)
unprovoked, continuing risk factors (ex. cancer)

A

transient, reversible risk factor (surgery)
- 1-3%

unprovoked, continuing risk factors (ex. cancer)
- 10%

38
Q

What type of VTE will recur that first year? What do the values mean?

A

Likely the same event
PE after initial PE (60% of episodes)
DVT after initial DVT (80% of episodes)

  • Mortality from recurrent VTE is 2-3x higher after PE than DVT
39
Q

What is the prothrombin time PT ?

A

the length of time it takes from the addition of calcium until the plasma clots

40
Q

What does the prothrombin time first developed to measure?

A

First for liver function
- now measures the extrinsic and common coagulation cascades

41
Q

What is the method of making the prothrombin time test?

A

decalcified plasma mixed with tissue factor (thromboplastin)
- calcium is added to initiate coagulation

42
Q

What was the problem with prothrombin time measurement?

A

Different labs using different thromboplastin which varied results

43
Q

What was the solution to prothrombin time

A

INR = PT patient / PT reference plasma (WHO)
- having a standard PT value

44
Q

What are the limitations and sources of error in INR testing

A

Limitations/sources of error:
1. Pretest: sampling/blood collection problems
2. Incorrect handling/storage of blood sample
3. Lab errors
4. Lupus anticoagulants (cause falsely elevated INR)
5. Taking INR during first few days of warfarin
- During this time, INR largely reflective of factor VII 7 (clotting factor with shortest half life)
- Thromboplastin concentration varies with factor VII levels
- INR will be falsely elevated during first few days of warfarin therapy
6. INR results >4.5
- The higher the reading the less certain it is

45
Q

What does the activated partial thromboplastin time?

A

Time it takes from the addition of calcium until the plasma clots

46
Q

What is the method of aPTT

A

Add to decalcified plasma
- phospholipid
- contact activator (kaolin)
- calcium, to initiate coagulation

47
Q

What does the aPTT measure? What does it monitor

A

INTRINSIC and common coagulation casade
- monitors unfractionated heparin UFH therapy

48
Q

What does the Anti-factor Xa assay measure?

A

Indirectly measures the concentration of anticoagulants that inhibit factor Xa

49
Q

What are the uses of anti-factor Xa assay?

A
  • LMWH therapy in special cases (pregnancy, renal impairment)
    • UFH therapy (when patient has factor XII deficiency or antiphospholipid antibodies)
    • DOACs with anti-Xa activity
50
Q

Effects of dabigatran, + rivaraxoban edoxaban and apixaban

with PT/INR

A

dabigatran
- varbiable effect, (INR <2 at peak blood levels)

rivaraxoban/edoxaban
- inc PT/INR

Apixiban
- minimal effect

50
Q

Effects of dabigatran, + rivaraxoban edoxaban and apixaban

with aPTT

A

dabigatran
- non-linear increase

rivaraxoban/edoxaban
- inc aPTT

Apixiban
- minimal effect

51
Q

Effects of dabigatran, + rivaraxoban edoxaban and apixaban

with antifactor Xa

A

dabigatran
- no effect

rivaraxoban edoxaban and apixaban
- Require specific calibrators (for each drug)
USE THIS TEST to measure levels of oral factor Xa-inhibitors

IPFC 3 Midterm 2 (7 decks)

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