ic4 (vte)

Question 1

How does VTE occur?

Answer 1

Virchow’s triad (All 3 must be present!)
Hypercoagulability
Vascular damage
Circulatory Stasis

Question 2

Symptoms of DVT (5 points)

Answer 2

Leg swelling
Pain
Warmth
Unilaterally (one leg)
Dilated superficial veins (palpable cord)

Question 3

Symptoms of PE

What about serious PE?

Answer 3

(symptoms similar to MI)
Cough
Chest pain, tightness
Shortness of breath
Palpitations
Hemoptysis (cough up blood)
Dizzy, lightheaded
Tachypnea (high breathing rate)
Tachycardia
Light headed
Distended neck veins

Serious PE
Cyanotic, Hypotensive, Hypoxic
Enter cardiogenic shock and die within minutes

Question 4

What should be done when DVT is suspected?

Answer 4

1) Wells-DVT Score (has good negative predictive value)

0 pts
Negative, DVT ruled out

1-2 pts
Moderate probability
Do D-Dimer
Positive: may or may not have DVT
Negative: no DVT
(D-Dimer +ve) Proceed with imaging or compression ultrasound

3 or more
Highly likely DVT
Proceed with imaging or compression ultrasound

2) Imaging / Compression ultrasound
To determine location of DVT

Proximal DVT
Initiate anticoagulation

Distal DVT
Can either initiate anticoagulation or surveillance

Question 5

How to treat PE? (3 steps)

Answer 5

Step 1: Diagnose PE using symptoms, risk factors, probability scoring
Virchow’s triad (risk factors)
Well’s criteria for PE
if > 4, PE likely
If 4 or less, do D-dimer
Symptoms eg. obstructive shock, hypotension (<90 or <40), end organ hypoperfusion (altered mental status, cold clammy skin)

Step 2: Identify mortality risk (low, intermediate, high)
High: Haemodynamic instability, symptoms, RV failure, Elevated cardiac troponin levels

Step 3: Decide treatment
High-risk
Thrombolytic (eg. Alteplase) + Heparin
Use Heparin (UFH), not LMWH!
Due to ease of reversibility

Intermediate to low risk
Use LMWH (instead of UFH) or DOACs
LMWH preferred over DOACs

Question 6

When are thrombolytics indicated? (2 points)

What thrombolytics should be used?

When should thrombolytics not be used?

Answer 6

1) High risk PE with hypotension (severe cardiopulmonary compromise)
2) DVT with high risk of limb loss

Use Alteplase + UFH (anticoagulant) in high risk PE
Tenecteplace not used for VTE

Thrombolytics should not be used in DVT as can increase risk of PE

Question 7

VTE treatment strategies

Answer 7

Oral (Apix and Riva are 3A4 substrates)
Apixaban
10mg BD for 7 days, then 5mg BD until 90 days
(extended 90+ days) 2.5mg BD from 6th month

Rivaroxaban
15mg BD for first 3 weeks, then 20mg OD until 90 days
(extended 90+ days) 10mg OD from from 6th month

Switch
UFH, LMWH (all SC), then
5 days
1) Dabigatran
150mg PO BD
2) Edoxaban
60mg PO OD

Overlap
Warfarin + UFH, LMWH for first 5 days until INR = 2
INR 2-3

Question 8

When should overlap therapy be used? (2 points)

Answer 8

When warfarin is indicated, aka
when CrCl < 30, but reduce dose of LMWH to 1mg/kg OD

Other indications of warfarin eg. Antiphospholipid syndrome, LVT, Prosthetic heart valve

Question 9

What are the checkpoints for VTE treatment? (what scenarios for each checkpoint?)

Answer 9

3 months and 6 months

All treatment should be minimum 3 months

Stop therapy at 90 days, if
1) Provoked DVT or PE with transient risk factor eg. road traffic accident
2) Unprovoked, but first distal DVT
3) First incident of PE due to transient risk factor

Continue anticoagulation after 90 days, if
1) Chronic risk factors eg. antiphospholipid syndrome, obesity
2) Unprovoked PE or proximal DVT
3) Recurrent VTE not related to transient or reversible risk factor

6 months (assuming pt has chronic risk factors)
Reduce Apix or Riva to “prophylaxis” doses eg. Apix 2.5 BD and Riva 10mg OD

Question 10

What are some risk factors in VTE used to determine duration of treatment?

Answer 10

Age (> 75 years)

Prior VTE history, esp if last VTE is <180 days
Recurrence is high

Virchow’s triad

Blood stasis
Hospitalisation
Surgery
Paralysis from injury
Immobility eg. casts, spinal cord injury
Obesity

Vascular injury
Major surgery
Trauma
Indwelling venous catheter

Hypercoagulability
Cancer
Factor 5 leiden
Protein C / S deficiency
Antithrombin deficiency
Antiphospholipid antibodies
Drugs eg. hormonal therapy (estrogen), cancer therapy, heparin induced thrombocytopenia)

Question 11

What anticoagulant should be used in pregnancy? What is the dose?

Answer 11

Enoxaparin (LMWH)

1mg/kg BD

Question 12

When should VTE prophylaxis be considered? (2 points)

Answer 12

1) After VTE treatment, beyond 6 months
2) To prevent 1st episode for medically ill patients or undergoing surgery (eg. patients undergoing abdominal surgeries, cancer patients)

Question 13

What is the MOA of Heparin / Enoxaparin?

How does the structure relate to their function?

Answer 13

Both catalyse the inactivation of Factor 10a by antithrombin

Heparin is longer chain than Enoxaparin. It can inactivate thrombin (2a). Thrombin is needed for conversion of Fibrinogen to Fibrin

Question 14

Dose of Heparin for VTE treatment

Answer 14

(IV): 80 units/kg bolus, then 18 units/kg per hour infusion

Question 15

Enoxaparin VTE treatment (normal VS severe renal impairment) dose

Answer 15

Treatment
1mg/kg Q12
(CrCl < 30ml/min) 1mg/kg OD

Question 16

Between Heparin and Enoxaparin,

1) Which is preferred? Why?

2) Which is used in severe renal impairment?

Answer 16

1) LMWH is preferred over UFH usually, unless there is a need for reversibility eg. in high risk PE patients
Hence UFH is used in high risk PE, whereas LMWH is used in low-intermediate risk patients

2) Both should not be used in severe renal impairment as monotherapy. Can use both overlap with Warfarin, or Apix instead

Question 17

Which DOAC is dialysable? Why?

Answer 17

Dabigatran, as it has low protein binding

Question 18

Which DOAC should not be used in good renal function?

Answer 18

Edoxaban (CrCl > 95ml/min)

Question 19

Which thrombolytic should be used in high risk PE? What is the dose?

Answer 19

Alteplase, 100mg over 2hr

Question 20

What is aPTT used to monitor

Answer 20

Heparin