31. Venous Thromboembolism Flashcards Preview

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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?

Virchow's triad:
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?

Antithrombin deficiency
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
Major trauma


What are some moderate acquired risk factors for VTE?

Previous VTE
Respiratory failure
Combined pill/HRT


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
Varicose veins

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
Ipsilateral odoema
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
Post-thrombotic syndrome
Congestive heart failure
Acute arterial occlusion


How can you diagnose DVT?

Pre-test i.e. the Well's scoring system

D-dimer test

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
Post-thrombotic syndrome


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
COPD exacerbation
Acute coronary syndrome
Aortic dissection
Lung cancer


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
Haemoptysis 1.0
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



Describe LMWH

Low molecular weight heparin
Agent of choice for VTE - more effective and safer than unfractionated heparin (UFH) and more predictable anticoagulant response
Subcutaneous administration
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
Fixed dose
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


Describe Warfarin

Vitamin K antagonist
Oral administration
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


What is a practical treatment used for VTE?

Graduated knee stockings can help the symptoms