VTE/anticoagulation Flashcards
How does tPA work?
Converts plasminogen to plasmin –> (1) cleaves fibrin and fibrinogen, (2) destroys coagulation factors, (3) blocks platelet aggregation
What’s Virchow triad?
Hypercoagulable state
Endothelial damage
Disruption to blood flow
How does the endothelial wall prevent thrombosis?
(1) Secrete tPA
(2) Secrete NO, and prostacyclin
(3) Block exposure to subendothelial collagen
(4) Secrete heparin-like molecules - augmentin antithrombin III
(5) Secrete thrombomodulin
List 5 examples of hypercoagulable states that make you prone to VTE
(1) Factor V leiden - mutated factor V that can’t be deactivated by protein C or S
(2) Protein C or S deficiency - Protein C or S normally inactivate factor V and VIII
(3) Prothrombin 20210A - increased prothrombin
(4) ATIII deficiency - heparin like molecules released from the endothelium normally activate ATIII which inactivates thrombin and coagulation factors
(5) OCP - estrogen increases production of coagulation factors
What is warfarin skin necrosis and how does it happen?
When you first take warfarin, you get temporary deficiency in protein C and S due to shorter half life
If you are already protein C or S deficient, and you take warfarin, it increases your risk of thrombosis, especially in the skin, leading to warfarin skin necrosis
How much of distal DVTs will extend proximally without treatment?
1/3
How much of proximal DVTs will become PEs without treatment?
15-25%
List 3 strong risk factors for VTE
Major surgery especially TKR, THR
Lip or hip fracture
Multiple trauma e.g. spinal cord injury
Wells score is not validated in …
Pregnancy
When do you thrombolyse PE?
Massive PE with haemodynamic instability
Has not shown improved survival in submassive PE (trop rise and RV dysfunction)
When are IVC filters indicated?
Can’t anticoagulate
Recurrent PE despite anticoagulation
How long can IVC filters stay in for?
2-4/52
If not, risk overgrowth around filter and then you won’t be able to remove it. Will need lifelong anticoagulation in that case.
Which NOACs can you use for DVT/PE?
Rivaroxaban and apixaban only
Duration of anticoagulation for
PE/proximal DVT
Distal DVT
PE/proximal DVT: minimum 3/12
Distal DVT: 6/52 - 3/12
Whether its provoked or unprovoked, will determine duration
Thrombophilia screen
Lupus anticoagulant (only one to do in the acute setting) Protein C, protein S Factor V leiden Anticardiolipin ab Prothrombin G20210A Antithrombin
When to do a thrombophilia screen?
Recurrent VTE VTE before age 45 Arterial and venous thrombosis (antiphospholipid) VTE at unusual places VTE while on OCP, HRT or pregnant Unprovoked VTE FHx of VTE
What’s post-thrombotic syndrome?
Clot damages valve –> fluid goes backwards –> venous hypertension –> reduced blood supply to muscle
Symptoms can mimic recurrent DVT - pain, oedema, heaviness, fatigue
Gets better with elevation and rest. Worst later in the day.
Rx post-thrombotic syndrome
If proximal DVT (ileofemoral), consider direct thrombolysis
Graduated compression stockings can improve symptoms of swelling but no benefit in RCT
What factors make it high risk for recurrent VTE?
Unprovoked proximal DVT/symptomatic PE (especially if more than one episode)
Active cancer
Antiphospholipid syndrome
Anti-thrombin deficiency
= indefinite anticoagulation
Consider indefinite anticoagulation in minimally provoked DVT/PE e.g. travel related, immobility (non-surgery), minor surgery
Indications for NOACs
DVT, PEs (except dabigatran)
Non-valvular AF
Post TKR
In what population groups do we have less experience with NOACs?
Obesity or BMI >40
Cancer - NOACs are accepted now
Antiphospholipid syndrome (particularly triple positive) - don’t use
In what population groups can we not use NOACs?
CrCl <30 Poor compliance (quick onset and offset) Extremes of weight Cancer Antiphospholipid syndrome Metal heart valves Valvular AF Lactation, pregnancy Child Pugh B, C
How does NOAC compared to warfarin?
Similar efficacy
Less serious bleeding especially ICH
Reversal agent for dabigatran
Praxbind/Idaricizumab (monoclonal ab)
Immediate reversal
