Flashcards in 31. Venous Thromboembolism Deck (32):
What is meant by 'thrombosis'?
Pathological clot (thrombus) formation within a blood vessel
What is an 'embolism'?
This is when the clot breaks off and travels through the blood circulation until it is obstructed by vessels of a smaller diameter
Briefly describe venous thrombi
These thrombi are more commonly the ones that cause deaths i.e. lead to heart attacks and strokes - predominantly formed of platelets
Briefly describe arterial thrombi
These are predominantly formed of fibrin
I.e. in the case of DVT and PE
What is the epidemiology of PE?
The epidemiology is age dependent: 1 per 5000 for 20 year olds, 1 per 1000 for 50 year olds and 1 per 100 in 90 year olds
Third most common cause of cardiovascular disease
Second leading cause of death in cancer patients
What is the main reason for the cause of death in patients with venous thromboembolism (VTE)?
Because a diagnosis is not made (rather than treatment failure) - this is because the symptoms can often be similar to that from other conditions
What are the causes of VTE?
Reduced blood flow - stasis i.e. in patients in hospital beds, planes
Vessel wall disorder
These can be due to heritable or acquired disorder although the majority of patients have it due to both a heritable and an acquired cause
Some causes are idiopathic
What are the main genetic risk factors for VTE?
Protein C deficiency
Protein S deficiency
Factor V Leiden
What are some strong acquired risk factors for WTE?
Fracture of hip/pelvis
Hip or knee replacement surgery
Major general surgery, especially for malignancy
What are some moderate acquired risk factors for VTE?
What are some weak risk factors for VTE and why is this important?
Bed rest for more than three days
Travel-related e.g. a long haul flight
These are important because although they are weak risk factors, the population is generally widely exposed to these factors
How does DVT generally present?
Erythema - superficial reddening of the skin
Palpable cord i.e. thrombosed vein
Superficial venous dilation
Why is the correct diagnosis of DVT ridiculously important?
Because about 90% of patients that present with a query DVT are found not to have DVT
The drugs used to treat DVT can cause serious/fatal side effects SO must not be given to someone who does not have it
What is the differential diagnosis for DVT?
Musculo-tendinous - trauma
Ruptured Baker's (popliteal) cyst
Congestive heart failure
Acute arterial occlusion
How can you diagnose DVT?
Pre-test i.e. the Well's scoring system
Confirm the diagnosis with radiology - a compression ultrasound radiograph
What is a D-dimer test and what is it testing for?
What is the problem with this test?
When a clot forms, insoluble fibrin is produced
When the clot is lysed by the embolytic process, D-dimer protein is produced SO indicates presence of a clot
BUT this is a non-specific marker - is commonly raised in other conditions too e.g. infection, cancer, inflammation, pregnancy
Give the Well's scoring system
Clinical characteristic Score
Active cancer within last 6 months 1
Paralysis, paresis, recent plaster immobilisation 1
Recently bedridden ≥ 3 days, major surgery <12 weeks 1
Localised tenderness along distribution of deep veins 1
Entire leg swollen 1
Calf swelling ≥ 3 cm (10 cm below tibial tuberosity) 1
Pitting oedema confined to symptomatic leg 1
Collateral superficial veins (non-varicose) 1
Previous documented DVT 1
Alternative diagnosis at least as likely as DVT -2
Total score: ≥ 2 – DVT likely; ≤ 1 – DVT unlikely
What complications can arise from DVT?
PE - fatal or non-fatal
Extension of a clot
Recurrent episode of VTE
What is post thrombotic syndrome and how common is this?
Recurrent pain and swelling in the leg - can lead to leg ulceration which can prove to be fatal
Occurs due to venous hypertension
Effects 30-40% of individuals with DVT
What is the clinical presentation of PE?
Pulmonary infarction/haemorrhage - breathlessness, pleuritic chest pain, haemoptysis
Isolated breathlessness - this is the hardest to be recognised as there are no other presenting features - can get treated for e.g. asthma instead
What are the signs of PE?
Crepitations and pleural rub
What investigations are used for PE?
ECG - sinus tachycardia, right heart strain, T-wave inversion
Chest x-ray - often normal, small pleural effusion
Arterial blood gasses - hypoxia, low CO2, can often be normal
What differential diagnoses are possible for PE?
Pneumonia or bronchitis
Acute coronary syndrome
Give the Well's score for PE
Risk factor Score
Clinical signs and symptoms of DVT 3.0
Alternative diagnosis less likely than PE 3.0
Pulse >100 1.5
Immobilisation or surgery in previous 4 wks 1.5
Previous DVT or PE 1.5
Cancer (within last 6 months) 1.0
Probability: > 4 PE likely; ≤ 4 PE unlikely
What is the prognosis of a PE?
10% mortality within 1 hour of symptom onset
30% mortality within 2 weeks if not treated
If treated, PE mortality reduces to less than 5%
All cause mortality at one year is 25% due to cancer and cardiorespiratory disease
What is the management plan for venous thromboembolism?
Start LMWH whilst confirming the diagnosis
Once this is confirmed, start warfarin
Stop heparin after a minimum of five days once the INR is in the therapeutic range
Continue warfarin and review this at three months
Low molecular weight heparin
Agent of choice for VTE - more effective and safer than unfractionated heparin (UFH) and more predictable anticoagulant response
Half life of about four hours
No monitoring unless the patient has renal failure, is pregnant or obese
Half life of four hours
What is Fondaparinux and when can it not be used
Anticoagulant - synthetic pentasaccharide
Half life of eighteen hours
Unsuitable if renal impairment
What are the side effects of Heparin usage?
Major bleeding occurs in 1-5% in the first week of treatment
Heparin-induced thrombocytopenia (deficiency of platelets in the blood causing bleeding into the tissues, bruising and slow blood clotting after injury)
Osteoporosis with exposure to heparin for several weeks or more
Vitamin K antagonist
Long half life of 36 hours
Delayed onset of action
Primarily affects INR (prothrombin time converted to ratio)
Multiple drug interactions
This is teratogenic so should avoid in pregnant women
BUT reduces the risk of recurrence during treatment by 90%
What surgical treatments can be used for venous thromboembolism?
Thrombolysis - 'clot bursting therapy' used in massive PE or limb-threatening DVT
Inferior vena cava filter used if major contraindication to anticoagulation or if recurrence of PE despite adequate anticoagulation