Thrombotic Disorders Flashcards
Venous thrombo-embolism
the process of blood clot formation in the veins
Diagram terminology page
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Provoked Venous thrombo-embolism definition
clear precipitating cause from history or tests
Unprovoked Venous thrombo-embolism definition
no clear cause
Thrombophilia definition
where the blood in the body clots more easily than normal
Why do venous thrombo-embolisms occur? What are the main categories called?
Virchow’s triad
circulatory stasis
vascular injury
hypercoagulable state
Virchow’s triad
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Why do venous thrombo-embolisms occur?: circulatory stasis:
- where the blood is not flowing in the way it
should be - bed rest, hence valves in veins aren’t used
as they should be so blood flow becomes
stagnant, clotting proteins become more
activated and a blood clot forms - lower limb ortho surgery
- major abdominal surgery
- pregnancy
- long haul flights/long car journeys
Why do venous thrombo-embolisms occur?: hypercoagulable states:
- the body is in a state of producing clotting
proteins more than they normal should,
which can activate the clotting processes in
the body - smoking
- oestrogens (oral contraceptives, HRT)
- active cancer
- inherited and acquired thrombophilias
Why do venous thrombo-embolisms occur?: Vascular Injury:
- direct damage to a vessel carrying blood
- limb trauma (including surgery)
- foreign bodies
- cannula, pacemaker wires
- sepsis
- bacteria, toxins
- previous DVT
- May Thurner Syndrome = pinch where iliac
vein and artery overlap so narrowed left
iliac vein due to pressure from right iliac
artery
What is the most common inherited thrombophilia? Related %s.
- Factor V Leiden
- mutation of the factor V gene
- 5% of UK population
- only 10% of people with Factor v Leiden
have thrombosis hence genotype vs
phentotype factors
What is the 2nd most common inherited thrombophilia?
- prothrombin thrombophilia
- mutation of Factor II gene
Other Inherited thrombophilias:
- protein C deficiency
- protein S deficiency
- hereditary anti-thrombin deficiency
- congenital dysfibrogenemia
When to test for inherited thrombophilias?
- if patient has had an unprovoked DVT or
PE and those who have a first degree
relative who has had DVT or PE if it is
planned to stop anticoagulation treatment - do not routinely offer thrombophilia
testing to first degree relative of people
with a history of DVT or PE and
thrombophilia - do not offer testing for hereditary
thrombophilia to people who are
continuing anticoagulation treatment
anyway - do not off thrombophilia testing to people
who have had a provoked DVT or PE
Why do we not test everybody for inherited thrombophilias?
- expensive
- there are many more inherited
thrombophilias than what we can test
them hence do not want to falsely reassure
patients
Acquired Thrombophilias:
- most common?
- is?
- affects men or females more?
- associated with
- risks
- most common is antiphospholipid
syndrome - autoimmune disorder: antibodies attack
phospholipids - more female than men
- 10-15% associated with systemic lupus
erythematous have antiphospholipid
syndrome - increased risk of pregnancy complications:
miscarriage, stillbirth, pre-eclampsia
When to consider testing for antiphospholipid antibodies in patients?
patients who have has an unprovoked DVT or PE if it is planned to stop anticoagulation treatment
Acquired thrombophilias:
- 2nd most common/
- is? (1)(4)
- acquired dysfibrinogenaemia
- fibrinogen is a part of clotting cascade,
helps to form a stable plug - fibrinogen is dysfunctional due to:
- severe liver disease (most
common)***
- autoimmune disease (Rh arthritis)
- plasma cell dyscrasias
- certain cancers (eg cervical)
Insert Vascular injury diagram illiac veins
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Most common site for deep vein thrombosis
- leg > arm
- calf = popliteal and tibial veins
- thigh = femoral and iliac veins
DVT in legs signs:
- unilateral calf swelling
- heat
- pain
- erythema (redness)
- hardness
Why are DVTs easy to miss?
- can be no signs and symptoms
Differential Diagnoses for blood clot:
- Baker’s cyst = ruptured aneurysm behind
the knee - Cellulitis = inflammation and infection of
skin - Muscular pain/strain after injury
- history is key
DVT investigations:
- D-dimer test = useful to rule out DVT if low
probability - Doppler ultrasound:
- investigation of choice: quick, safe
- real time 2D images
- colour doppler (duplex) shows
direction and velocity of blood flow
- thrombosed veins non-compressible - contrast venography rarely required, but
can be useful in extensive disease or to
look for anatomical malformations
D-dimer test:
- D-dimer is a breakdown product from
fibrin = fibrous mesh component of blood
clots - only present when the coagulation system
has been activated - elevated in venous thromboembolism
- very sensitive = negative test can be used
to rule out DVT/PE if low probability - not very specific = positive test is not diagnostic
- can occasionally be negative in “barn-door”
DVT/PE - do not use if high clinical probability
D-dimer diagram
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D-dimer may be higher in pregnancy:
pregnancy is a hyper coagulable state
hence more fibrinogen in pregnancy anyway
DVT treatment: Calf:
- symptomatic Rx (ibuprofen for pain)
- Repeat ultrasound in 7 days to ensure no
progression - reality we treat despite:
- anticoagulation with Direct Oral
Anticoagulant (DOAC)
eg: Rivaroxaban, Dabigatran *** - 3-6 months for 1st event
- lifelong for second event
- warfarin for renal dysfunction
- thrombophilia testing if 1st degree relative
with VTE
DVT treatment: Ilio-femoral DVT:
- anticoagulation with Direct Oral
Anticoagulant (DOAC)
eg: Rivaroxaban, Dabigatran *** - 3-6 months for 1st event
- lifelong for second event
- warfarin for renal dysfunction
- thrombophilia testing if 1st degree relative
with VTE
Pulmonary embolism: Microemboli:
asymptomatic
Pulmonary Embolism: Small, peripheral:
- pleuritic pain
- breathless
- haemoptysis
Pulmonary Embolism: Large, central:
- chest pain
- breathless
- hypoxia
Pulmonary embolism: Massive:
- syncope
- shock
- tachycardia
- death
investigations for pulmonary embolism:
- Oxygen sat low
- ABG low PaO2
- ECG: sinus tachycardia (fast HR), S1, Q3,
inverted T3, right heart strain - ***CT pulmonary angiogram (CTPA) is the
investigation of choice in a suspected PE
CTPA PE
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Justifying the use of CTPA:
- CTPA carries a high radiation dose:
- only used if there is a reasonable
likelihood of PE
- consider alternative approach in some
groups of patients - Wells score used to guide investigation
- Low probability:
- D-dimer first
- CTPA is D-dimer positive
Alternative approach to CTPA:
- ventilation - perfusion scan
Ventilation - Perfusion Scan
- uses inhaled and injected radioisotopes
- looks for a mismatch of lung ventilation
and perfusion - limited use if underlying lung disease
Contraindications for CTPA:
- severe contrast allergy
- severe renal dysfunction
- high risk from radiation
(pregnant/breastfeeding)
PE treatment: Anticoagulation:
- consider co-morbidities, contraindications
and patient preferences (bleeding risk
assessed with HASBLED scoring system - consider special circumstances: renal
function, extremes of body weight, cancer
thrombosis, APLS - Large PE: initially heparin, usually sc
low molecular weight heparin
(Enoxaparin) - then convert to:
- warfarin or
- DOAC (rivaroxaban, dabigataran ***)
- 3-6 months for first event
- lifelong for second event/ persistent
risk factors - smaller PEs can go straight to DOAC
- thrombophilia testing if 1st degree relative
with VTE
29 year old woman, smoker, overweight on combined contraceptive pill, recent trip to USA, acute chest pain, collapsed at home, bought to A&E:
- cold, sweaty, agitated
- pulse 150bpm, BP 75/65, RR 24/min, SO2
91% on 60% O2 - JVP +10cm
- heart sounds normal, chest clear
- chest x ray: normal
Treatment for massive PE:
- IV fluids
- IV heparin infusion
- consider thrombolysis***:
- if a patient has shock and right heart
strain
- benefit vs bleeding risk: 10% risk of
major bleeding
- not because clot looks big on CT - other options: surgical embolectomy,
catheter fragmentation
PE is cause of death in what % of patient post mortems?
10-30%
What % of VTE events occur <90 days of hospital discharge?
50%
VTE prevention:
- prophylactic low dose sc: heparin:
- low dose rivaroxaban after major joint
surgery - venous compression stockings
- pneumatic compression stockings (cant
give blood thinners during surgery) - early mobilisation
- good hydration
