Venous thromboembolism Flashcards
Define thrombosis
Pathological clot formation within blood vessel
Describe the difference between venous thrombi and arterial thrombi
Venous- red cells in fibrin mesh (red clot)
Arterial- platelets and fibrin (white clot)
Define embolism
Clot breaks off and travels through circulation until obstructed by vessels of smaller diameter
What is difference between distal and proximal DVT
Distal= confined to calf vein Proximal= involved popliteal vein and above
Where do majority of pulmonary embolisms arise from
DVT
Where do majority of DVTs arise from
Calf venous sinuses
What % of DVTs extend proximally to popliteal vein or above
25
Of the DVTs that extend proximally to popliteal vein, what % embolise
40
Of the DVTs that embolise, how many are fatal
20
What is the third most common cause of cardiovascular death
Pulmonary embolism
What is the mortality of untreated and treated pulmonary embolism
30% untreated
<5% when treated
What are the causes of venous thromboembolism (Virchows triad)
Static blood
Vessel wall disorder
Hypercoagulability
Name the strong risk factors for VTE (5)
- Hip/ pelvis fracture
- Hip/ knee replacement
- Major general surgery
- Major trauma
- Spinal cord injury
Name the moderate risk factors for VTE (7)
- Previous VTE
- Cancer outpatient
- Resp failure
- Pregnancy
- Combined OC pill/ HRT
- Central venous line
- Thrombophilia
Name the weak risk factors for VTE (5)
- Bed rest > 8 days
- Travel
- Obesity
- Day case srugery
- Varicose veins
Signs and symptoms of DVT (8)
Tenderness Erythema Pain Palpable cord Superficial venous dilation Ipsilateral oedema Warmth Swelling
Why is it important to get objective diagnosis of DVT
- 75% of suspected patients negative on investigation
- Drugs used to treat VTE cause serious side effects
3 steps of diagnosing DVT?
1) Clinical pre-test probability (Wells score)
2) D-dimer test
3) Radiological assessment
What is D-dimer
Blood test for non specific marker of fibrin formation
What radio-logical assessment is usually used to diagnose DVT and why?
Compression ultrasound as non invasive
Gold standard for radiological assessment
Venography
Name some components of a Wells score test
Active cancer Paralysis Recently bedridden Localised tenderness Entire leg swollen Calf swelling Pitting oedema Collateral superficial veins Previous documentated DVT`
What is post-thrombotic syndrome
Recurrent pain and swelling in leg that may progress to local skin pigmentation and ulceration
Is post-thrombotic syndrome more or less common in distal or proximal DVT
Proximal (30-50% of proximal cases)
What causes post-thrombotic syndrome
Occurs due to venous hypertension (obstruction and valve damage) as well as abnormal microcirculation with reversal of blood flow from deep to superficial veins
Signs of pulmonary embolism
Tachypnoea and tachycardia
Crepitations
Pleural rub
What % of PE patients have isolated breathlessness
25
What % of PE patients have collapse/ hypotension/ shock
10
What does an ECG of somebody with PE show
Sinus tachycardia
Right heart strain
T wave inversion
S1Q3T3
What would chest x-ray show
Focal oligaemia
Peripheral wedge shaped density above diaphragm
Arterial blood gases show hypoxia, low CO2