257/258/260 - Too Much Clotting Flashcards
Thrombophilia, VTE, Anticoagulant therapy for VTE
Compare the relative and absolute risk of thrombosis with the inherited thrombophilias
Relative risk increases several fold
Absolute risk remains relatively low; can become higher when combined with another risk factor (OCPs, smoking), but still low enough that we don’t need to screen for thrombophilias before prescribing OCPs
What 3 antibodies are associated with antiphospholipid antibody syndrome?
- Lupus anticoagulant
- Anti-beta 2 glycoprotein antibody
- Anti-cardiolipin antibody
- -> Arterial and venous thrombosis, pregnancy complications*
- Dx requires lab criteria (antibodies) and clinical criteria (thrombosis or obstetric complications)*
What is the inhibitor for dabigatran?
Idarucizumab
List the 2 major categories of directa acting oral anticoagulants
-
Anti-Xa agents (-xaban)
- Rivaroxaban
- Apixaban
- Endoxaban
-
Direct thrombin inhibitors (-gat-, -rudin)
- Argatroban
- Dabigatran
- Bivalirudin
Is the following characteristic of arterial or venous thrombus?
Red (rich in RBCs)
Venous
What comorbidity increases bleeing risk in patients on LMWH?
Renal failure
What enzyme activates clotting factors II, VII, IX, and X?
What is the cofactor?
VKOR
Vitamin K
VKOR is the target of Warfarin
What is the most common cause of VTE?
Abnormal blood flow
- Bedrest
- After surgery
- Long flights
How long after starting therapy does it take for warfarin to achieve full therapeutic effects?
5 days
- FVII will drop first (shortest half life)
-
Not considered therapeutic until FII drops
- Mus decrease below 20%
- Use a heparin bridge if immediate anticoagulation is necessary
A clot in which veins are most likely to embolize to the lungs?
Deep > superficial
Proximal > distal
Proximal lower extremity clots are most likely to cause PE
List 2 low-molecular weight heparin agents
Enoxaparin
Dalteparin
List 4 complications of VTE
- Death
- Recurrent thrombosis (VTE again)
- Post-thrombotic syndrome
- Pulmonary hypertension (CETPH)
What is the goal INR for Warfarin therapy?
2-3
Which outpatient anticoagulant is safest to use in renal disease?
Warfarin - not excreted renally
- Of the DOACs, Apixiban relies least on renal excretion*
- For inpatient/acute setting, unfractionated heparin is safe in renal disease, but NOT LMWH or fondaparinux*
What inherited thrombophilia results in relative heparin resistance?
Antithrombin deficiency
Heparin works by potentiating the effects of antithrombin
List 2 demographics for whom direct roal anticoagulants should not be prescribed
Pregnant patients
Patients with renal failure
What are the indications for thrombolytic therapy in VTE?
- Systemically if massive PE (hemodynamic instability)
- Catheter-directed:
- If DVT is life or limb threatening
- If PE is submassive but high risk
What imaging method is most commonly used for suspected PE?
What method is gold standard?
- Commonly used = CT pulmonary angiogram
- Gold standard = Angiography
- High clinical probability -> CTPA*
- Low or intermediate with positive D-dimer -> CTPA*
Which clotting factors are inactivated by protein C? (2)
Va, VIIIa
Protein C cleaves Va, and then V helps protein C cleave VIIIa
When would an IVC filter be used to treat VTE?
If a pt has acute PE or proximal DVT and cannot tolerate therapeutic anticoagulation
Is unfractionated heparin safe to use in patients with renal disease?
Yes
List 3 loss of function inherited thrombophilias
- Protein C deficiency
- Protein S deficiency
- Antithrombin deficiency
What clotting factors are inhibited by antithrombin?
IIa, Xa
(T-wo and T-en) by Anti-T
- Note: heparin drugs potentiate the effects of antithrombin*
- Heparin: inactivates IIa, Xa*
- LMWH: more specific for Xa*
- Fondaparinux: Most specific for Xa, minimal effects on IIa*
- IIa = thrombin*
Which inherited thrombophilia mutation is associated with the greatest risk of thrombosis?
Factor V Leiden
Venous thrombosis most common