16 - Venous Thromboembolism Flashcards
Where do the majority of DVT originate from
calf venous sinuses
Is PE common
3rd most common cause of CV death
What are the causes of DVT
Virchow’s triad
- Reduced blood flow – stasis
- Vessel wall disorder
- Hypercoagulability
What percentage of DVT are heritable, acquired and idiopathi
Heritable – 25%
Acquired – 50%
Idiopathic – 40%
What are some genetic risk factors for DVT
Antithrombin deficiency
Protein C, S deficiency
Factor V Leiden
Prothrombin gene mutation
Strong risk factors for DVT
Hip/pelvis fracture
Hip or knee replacement surgery
Trauma
Moderate risk factors
Pregnancy
Cancer
Combined OC picc
Weak risk factors
Bed rest > 3 days
Obesity
Varicose veins
Presentation of DVT
Pain Swelling Warmth Oedema (usually unilateral)
Why is objective diagnosis important in VTE
Drugs used to treat VTE cause serious side effects
Differential diagnosis
Post thrombotic syndrome
Cellulitis
Lymphoedema
Congestive heart failure
How do you diagnose DVT
1) Clinical pre test probability
2) D dimer test
3) Radiological assessment - Compression ultrasound, Venography (Gold standard)
What is the D-dimer test
blood test for non-specific marker of fibrin formation (usually raised in VTE but also in cancer, infection, inflammation, post-op, pregnancy)
What is post-thrombotic syndrome
Recurrent pain and swelling in the leg
more common with proximal DVT
What is the cause of post-thrombotic syndrome
Venous hypertension (obstruction and valve damage) Abnormal microcirculation with reversal of blood flow from deep to superficial veins
What are some signs and symptoms of a pulmonary embolism
Breathlessness
Pleuritic chest pain
Tachypnoea and tachycardia
Crepitations and pleural rub
What preliminary examinations would you carry out in a PE
ECG - sinus tachycardia,S1Q3T3 pattern
CRX - often normal, may see peripheral wedge shaped density above diaphragm
Arterial Blood Gas
All these can rule out other conditions
What is the differential diagnosis for PE
Pneumonia Asthma Pneumothorax Lung Cancer COPD
What are the diagnostic tests for PE
Pulmonary Angiogram - Gold standard
D-dimer
pre-test probability (wells)
Isotope lung scan
Prognosis of PE
If treated the prognosis is a lot better and mortality risk reduced to <5%
What is the acute treatment of DVT and PE
IV heparin
SQ LMWH
SQ Fondaparinux
What is the short term treatment of DVT and PE
Warfarin
SQ LMWH
What is the long term treatment of DVT and PE
Warfarin
LQ LMWH
ASA (Aspirin)
What blood tests would you ask for a patient with suspected DVT/P
FBC, clotting screen (PT and APTT), D-dimer, U&Es/LFTs
Why is LMWH used instead of UFH
LMWH - SQ administration, 4hour half life, Fixed dose, no monitoring needed
UFH - IV administration, 60-90min half life, have to monitor with APTT, Variable adjusted dose
What is the difference between the use of heparin and warfarin
Heparin is faster acting so would first use heparin for minimum of 5 days with warfarin as it takes a few days for warfarin to start working
What is the therapeutic range for the INR
2.0-3.0
What is Fondaparinux
Synthetic pentasaccharide
An anticoagulant that inhibits factor X
Has a 18 hour half life
What drugs work on factor Xa
Apixaban
Endoxaban
Rivaroxaban
How does heparin work
Activates antithrombin so thrombin is inactivated
How does warfarin work
VitaminK antagonist
Prevents clotting factors 2, 7, 9 and 10, as well as the regulatory factors protein C, protein S, and protein Z.
What is the half life of warfarin
36 hours
What are the risk of warfarin
Has teratogenicity so not given to pregnant women as a risk to fetus
Major bleeding
What can you use if you need to reverse the effects of warfarin
Prothrombin complex concentrate - contains the missing clotting factors
What are some side effects of heparin
Major bleeding
Heparin induced thrombocytopenia
Osteoporosis
Eg of a heparin antagonist
Protamine sulphate
What do you give to a pregnant woman with VTE
LMWH
AVOID WARFAIN AND DOAC as they cross the placenta
What do you give to a breastfeeding woman with VTE
LMWH and Warfarin are fine
but not DOACs
What do you give to a patient with cancer associated thrombosis
LMWH (more effective than warfarin)
DOAC - under evaluation
What is the risk of recurrence of VTE after stopping anticoagulants
Depends on reason for initial event
Overall initially 5% risk in 1 year
30% by 10 years
= If provoked by transient risk factor – 1-4% in 1st year
= If unprovoked or persisting cause – 5-10+% in 1st year
When are thrombolytics used and what do they do
Clot busting
used in massive PE or limb threatening DVT
When is a inferior vena cava filter used
if major contra-indication to anticoagulation or if recurrence of PE despite adequate anticoagulation
What are the percentages of thrombophilia due to -
Factor V Leiden Prothrombin gene mutation Protein C deficiency Protein S deficiency Antithrombin deficiency
Factor V Leiden - 15% Prothrombin gene mutation - 5% Protein C deficiency - 1-2% Protein S deficiency - 1-2% Antithrombin deficiency - <1%
What does protein C do
inactivates factors Va and VIIIa
What does protein S do
Cofactor for Va and VIIIa inactivation by protein C
What is antiphospholipid syndrome
Acquired form of thrombophilia
Diagnosed with thrombosis and pregnancy morbidity AND lab criteria (Lupus anticoagulant, anticardiolipin antibodies, anti-b2glycoprotein 1 antibodies)
