Thromboembolism in Pregnancy (DVT, PE) Flashcards
Define
Definition
DVT: Thrombus formation in the deep veins of the legs (leading to impaired blood flow), causing leg swelling and pain
PE: Thrombus formation in the distal veins of the lungs (deep venous system)
Occurs as a result of venous stasis, trauma and hypercoagulability (Virchow’s triad)
Epidemiology
- MOST COMMON cause of direct maternal death in the UK
- Pregnancy is associated with a 6-10 fold increase in risk of VTE compared to non-pregnant women
Aetiology
Pregnancy is a hypercoagulable state due to alterations in thrombotic and fibrinolytic systems
There is an INCREASE in:
- Clotting factors VIII, IX, X
- Fibrinogen
There is a DECREASE in:
- Protein S
- Antithrombin (AT)-III
- This is suggested to be an evolutionary response to reduce the likelihood of haemorrhage following delivery
- The weight of the gravid uterus increases pressure on the IVC, leading to venous stasis and thereby further increasing the risk of thromboembolism. Hence more likely on the left hand side!
Thrombophilia
Major hereditary forms of thrombophilia currently recognised are:
Deficiencies of endogenous anticoagulants Protein C, Protein S, AT-III
Abnormalities in procoagulant factors
Factor V Leiden (caused by mutation in Factor V gene)
Prothrombin mutation G20210A
Acquired thrombophilia is most commonly associated with anti-phospholipid syndrome
This is the combination of lupus anticoagulant +/- anticardiolipin antibodies with a history of recurrent miscarriage and/ or thrombosis.
It may be associated with SLE or other autoantibody disorders
Risk factors
Pre-existing:
- Maternal age > 35 years
- Thrombophilia
- Obesity (> 80kg)
- Previous TE
- Severe varicose veins
- Smoking
- Malignancy
Specific to pregnancy:
- Multiple pregnancy
- Pre-eclampsia
- Grand multiparity
- Caesarean section (especially if emergency)
- Damage to pelvic veins
- Sepsis
- Prolonged bed rest, travel (> 4 hours)
Signs and Symptoms
DVT – red, hot, swollen tender calf, unilateral lower limb oedema, erythema, tenderness, low grade pyrexia
PE – pleuritic chest pain, dyspnoea, cough, haemoptysis, tachycardia, tachypnoea, low-grade pyrexia, reduced O2 saturations, cardiorespiratory collapse, chest signs (reduced air entry, crepitations), loud P2 sound
Investigation
Heparin augments AT-III -> less F10a, less F2a (thrombin) / less thrombin -> less 13, 11, 8, 5, TM
Examination of the LEG and cardiorespiratory examination
Basic observations
- Bloods
- FBC
- U+Es
- LFTs
- Coagulation screen
DVT
- Compression USS is the first investigation used in suspected DVT
- High sensitivity and specificity in diagnosing proximal thrombosis
NOTE: A thrombus confirmed purely to the calf vein is unlikely to lead to a PE
Venography is invasive (requires contrast injection and use of X-rays) but allows excellent visualisation of veins above and below the knee
USS of lower limbs
- PE
- ECG
- CXR
- ABG
- Ventilation Perfusion (V/Q) scan
- CTPA
IMPORTANT: in pregnancy, the D-dimer is physiologically elevated already so it is useless to do it
Management
Overview of management
1st Line: SC LMWH (Clexane)
- Does not cross the placenta
- As safe and effective as unfractionated heparin with lower and fewer haemorrhagic complications
- Following delivery, women can choose to convert to warfarin
- LMWH and warfarin are both safe in breastfeeding
Any woman with signs or symptoms suggestive of VTE should have objective testing and treatment with LMWH(until diagnosis is excluded)
- If suspected PE in the presence of confirmed DVT- treat with therapeutic dose LMWH IMMEDIATELY.
- The therapeutic dose should be calculated based on the woman’s booking or early pregnancy weight
DVT
Compression duplex USS should be performed if there is clinical suspicion of DVT
- If NEGATIVE and low clinical suspicion – STOP anticoagulants
- If NEGATIVE and high clinical suspicion – STOP anticoagulants and repeat USS on days 3 and 7
Initial management includes elevating the leg and applying a graduated elastic stocking (i.e. TED stockings)
PE
- Women presenting with signs and symptoms of PE should have an ECG + CXR
- ECG- S1Q3T3 changes
- If the CXR is abnormal and there is clinical suspicion of PE, a CTPA should be performed in preference to a VQ scan
If they only have symptoms of DVT, then compression duplex USS should be performed
If they have NO symptoms of DVT, a VQ scan or CTPA should be performed
- CTPA- slightly increases maternal breast cancer risk
- V/Q- slightly increases risk of childhood cancer
Alternative or repeat testing should be carried out if the VQ scan and CTPA are normal but the clinical suspicion of PE remains
Anticoagulant treatment should be continued until PE is DEFINITIVELY excluded
NOTE: IVC filters may be considered in the peripartum period for patients with iliac vein VTE or in patients with proven DVT and those who have recurrent PE despite anticoagulation
MASSIVE PE
- Options include IV unfractionated heparin, thrombolytic therapy, thoracotomy or surgical embolectomy
- IV unfractionated heparin is the preferred initial treatment in massive PE with CV compromise
- Urgent portable echocardiogram or CTPA should be arranged
- If massive PE is confirmed, immediate thrombolysis should be considered
Maintenance Treatment of VTE
Treatment with therapeutic doses of SC LMWH should be continued for the remainder of the pregnancy and for at least 6 weeks postnatally and until at least 3 months of treatment in total
Routine measurement of peak anti-Xa activity for patients on LMWH for treatment of acute VTE in pregnancy or postpartum is not recommended except in women at extremes of body weight (less than 50 kg and 90 kg or more) or with other complicating factors (for example, with renal impairment or recurrent VTE).
- Women should be taught to self-inject
- Watch out for heparin-induced thrombocytopenia and heparin allergy
- Women should be offered a choice of LMWH or PO anticoagulant (this requires routine INR monitoring)
- NOACs may be used in patients who cannot tolerate heparin
NOTE: neither heparin nor warfarin are contraindicated in breast feeding
Anticoagulation during labour and delivery
- If VTE occurs at term, IV unfractionated heparin should be considered
- If a woman on LMWH maintenance therapy goes into labour, they should NOT inject any more
- If delivery is planned, LMWH should be discontinued 24 hours before
- Regional anaesthetic (e.g. epidural) should NOT be undertaken until AT LEAST 24 HOURS AFTER last dose of LMWH
- LMWH should NOT be given until 4 hours after the use of spinal anaesthesia or after the epidural catheter has been removed
- Women who are at HIGH RISK of HAEMORRHAGE who require continuous heparin should be managed with IV unfractionated heparin
Thrombolysis is contraindicated in pregnancy as it can cause catastrophic haemorrhage of the placenta and the foetus.
Prevention of Post-Thrombotic Syndrome
- Prolonged use of LMWH (> 12 weeks) is associated with LOWER risk of post-thrombotic syndrome
- Graduated elastic stockings should be used initially and worn for 2 years following DVT to prevent post-thrombotic syndrome
NOTE: Vitamin K antagonists e.g. Warfarin cannot be used in pregnancy as they have adverse effects on the foetus. They cannot be used in the 1st trimester due to teratogenicity and in the 3rd trimester as it causes foetal intracranial haemorrhage at delivery. Some women are given it for a short window of time in between e.g. if have metallic heart valves. However both heparin and warfarin can be used when breast feeding.
Complications
Complications
- DVT may lead to PE
- PE can be FATAL
- Heparin induced thrombocytopaenia
- Heparin allergy
- Risk of VTE increases 5-fold during pregnancy and the puerperium
- Majority of fatal TEs occur in the puerperium and are more common after Caesarean section
Prognosis
- Most patients do not get VTE if on thromboprophylaxis.
- Inadequate prophylaxis may lead to VTE
