Clots Flashcards
What is thrombosis?
Refers to formation of clot within a vessel (vein or artery).
How does thrombosis occur?
Blood coagulates, causing platelets to aggregate. This forms fibrin mesh.
Fibrin + platelet = clot
Remember Virchow’s triad.
What is Virchow’s triad?
- Hypercoagulability of blood
- coagulation is more likely to occur, for e.g. in cancer like leukaemia, thrombophilia, inflammatory disease - Vessel wall injury
- endothelial injury from trauma, surgery, chemical irritation, inflammation - Stasis of blood
- loss of laminar arterial flow
- poor blood flow e.g. sitting in long hrs flight, limited movement
- varicose veins
- venous obstruction
What is embolism?
Refers to when a piece of blood clot, foreign object, or other bodily substance (fat or bubble air) is carried through the circulatory system and cause blockage further down the line as blood vessels get narrower and smaller towards the organs.
E.g.
- stroke (clot in the brain)
- pulmonary embolism (clot in the lungs)
- deep vein thrombosis (clot in the leg)
Can you get blood clot outside of vessels? Give examples?
Yes
Refers to solidification of blood outside blood vessels or within vessels after death.
E.g.
- bruising (aka haematoma)
How is stroke caused?
Embolism
Carotid artery (neck) containing plaque (atherosclerosis)/ischaemia OR pt has AF where the heart is not pumping properly and increases the risk of developing a blood clot→ plaque/clot breaks off and travels to the brain → gets stuck/blockage in the vessel → stroke
How is heart attack caused?
Embolism
Coronary artery containing plaque (atherosclerosis) → plaque/clot breaks off and travels down the vessels → gets stuck/blockage in the vessel in a certain part of the heart → heart attack
What is venous thromboembolism (VTE)?
A blood clot (thrombus) forms in a vein, for e.g. in the deep vein.
This clot can travel (embolise) from the deep vein, through the right side of the heart and into the lungs, causing pulmonary embolism (PE).
Another word for blood clot?
Thrombus
Other types of embolism?
Cardiothoracic surgery/ divers → leads to air/gas bubble → stroke/heart attack
Amniotic fluid embolism
- rare
- occurs by amniotic fluid entering the mother’s circulatory system via tears in placental membrane/uterine vein rupture → leads to disseminated intravascular coagulation
Paradoxical embolism
- rare
- clot travels from one side of the heart to the other side.
Risk factors for venous thromboembolism (VTE)?
Immobility (bed bound)
Recent surgery
Long haul travel
Pregnancy
Hormone therapy with oestrogen
Malignancy
Polycythaemia
Systemic lupus erythematosus
Thrombophilia
What is deep vein thrombosis (DVT)?
Refers to the formation of a thrombus (blood clot) in a deep vein, usually in the legs, which partially or completely obstructs blood flow.
Presentation of DVT?
Unilateral localised throbbing pain
Pain occurs when walking or bearing weight
Calf or leg swelling
Tenderness to the calf (particularly over the site of the deep veins)
Dilated superficial veins (vein distention)
Skin changes
- oedema
- redness
- warmth
How to examine for DVT?
Measure the calf circumference just 10cm below the tibial tuberosity and compare with asymptomatic leg.
Difference of >3cm = increases probability of DVT
What is Wells score? What factors does it consider? What are the next steps depending on the score?
Assesses the likelihood of DVT and inform further management.
The total score ranges from -2 to 10.
If the score is 2 or more, then DVT is likely and an US doppler is needed within 4 hours.
- If not, offer d-dimer test, interim anticoagulation (e.g. rivaroxaban), followed by proximal leg vein US.
If the score is 1 or less, DVT is unlikely, but test for d-dimer within 4 hours. If not, offer interim anticoagulation (e.g. rivaroxaban).
- +ve d-dimer = offer proximal leg vein US
- -ve d-dimer = stop interim anticoagulation, consider alternative diagnosis
- active cancer (1)
- bedridden recently >3days or major surgery within 12 wks (1)
- calf swelling >3cm (1)
- collateral (non-varicose) superficial veins present (1)
- entire leg swollen (1)
- localised tenderness in deep vein site (1)
- pitting oedema in symptomatic leg (1)
- Paralysis, paresis, or recent plaster immobilization of the lower extremity (1)
- previous documented DVT (1)
- alternative diagnosis is at least as likely as DVT (-2)
What are the possible investigations for DVT?
Wells score
US doppler scan
Proximal leg vein US
D-dimer test
How is DVT managed?
Refer immediately for same-day assessment if suspected DVT in:
- pregnant woman
- woman given birth within the past 6 wks
Likely to have DVT:
- offer proximal leg US within 4 hrs
- if US not available then, D-dimer test and interim anticoagulation and proximal leg vein US within 24 hrs
Unlikely to have DVT:
- offer D-dimer test within 4 hrs
- if results cannot be obtained within 4 hrs, offer interim anticoagulation (e.g. rivaroxaban or apixaban -DOAC),
- +ve d-dimer = offer proximal leg vein US
- -ve d-dimer = stop interim anticoagulation, consider alternative diagnosis
Other options instead of DOAC:
- warfarin (target INR 2-3)
- LMWH
- Unfractionated heparin
Treatment duration depends on whether the DVT was provoked or unprovoked.
- provoked (has major RF, known cause) = 3 months
- has non-modifiable RFs = lifelong anticoagulation
- has active cancer with DVT = DOAC or LMWH for 3-6 months
Unprovoked DVT = investigate for cancer and thrombophilia
What is pulmonary embolism?
Refers to a life-threatening condition where the formation of a blood clot in the pulmonary arterial vasculature, causing severe respiratory dysfunction.
Basically arises from a blood clot formed in the veins, e.g. DVT.
How does pulmonary embolism present in a pt?
Typical triad:
- Sudden-onset SOB
- Pleuritic chest pain
- Haemoptysis
Syncope
Tachypnoea
Tachycardia
Hypoxia
Low-grade pyrexia (fever)
Hypotension
Cyanosis
Signs of right heart strain
- raised JVP
-parasternal heave
- loud P2
Signs of DVT
- unilateral swollen calf/leg
- tender calf
- vein distention
- erythema
- warm to touch
Investigations pulmonary embolism (PE)?
ECG
- normal or sinus tachycardia
- massive PE: right heart strain (P pulmonale, right axis deviation, RBBB, non-specific ST/T wave changes)
- classic S1Q3T3 (deep S waves in lead I, pathological Q waves in lead III and inverted T waves in lead III)
CXR
- signs of pneumothorax and pneumonia
- Fleischner sign (enlarged pulmonary artery)
- Hampton’s hump (a peripheral wedge shaped opacity)
- Westermark sign (regional oligaemia)
CTPA (CT pulmonary angiogram)
- diagnostic test of choice for PE
- will show a filling defect in the pulmonary vasculature
V/Q scan – preferred if the patient has renal impairment, contrast allergy or is pregnant
Lower limb Duplex
– helpful if a DVT is thought to be the cause of the PE
- this IVx is first-line – before a CTPA – in pregnancy
Bloods:
- D-dimer
- FBC
- CRP
- U&E
- Clotting function
-ABG (type 1 respiratory failure and/or a respiratory alkalosis)
What is PERC score?
Rules out pulmonary embolism if none of the factors below are identified.
Score out of 8.
- age ≥50 (1)
- HR ≥100 (1)
- O2 sat <95% (1)
- unilateral leg swelling (1)
- haemoptysis (1)
- recent surgery or trauma (1)
- prior PE or DVT (1)
- hormone use (1)
What is Wells’ criteria for pulmonary embolism?
Risk stratifying pts with a suspected PE.
Total score 12.5.
If Well’s score is ≤4:
- D-dimer
- low D-dimer rules out PE
- if it raised, do CTPA or V/Q scan
If Well’s score >4:
- CTPA
- If CTPA -ve, suspect DVT do US doppler
- clinical signs and symptoms of DVT (3)
- PE is #1 diagnosis OR equally likely (3)
- HR >100 (1.5)
- immbolisation at least 3 days OR surgery in the last 4 wks (1.5)
- haemoptysis (1)
- prior PE or DVT (1.5)
- malignancy with tx within 6 months or palliative (1)
How is suspected pulmonary embolism managed?
Immediate hospital admission if suspect PE in pts with:
haemodynamic instability:
- cardiac arrest
- obstructive shock (systolic BP <90 mmHg, end-organ hypoperfusion)
- persistent hypotension
pregnant or have given birth within the past 6 wks
Wells score >4
- hospital admission for immediate CTPA, if not offer interim anticoagulation
Wells score <4
- D-dimer test within 4 hrs, if not offer interim anticoagulation
- +ve D-dimer = CTPA, or interim anticoagulation
- -ve D-dimer = stop interim anticoagulation, alternative diagnosis
Before starting on interim anticoagulation, do baseline blood tests (FBC, renal, liver, prothrombin time, activated partial thromboplastin time).
How is confirmed pulmonary embolism (PE) managed?
Anticoagulant tx (DOAC -rivaroxaban or apixaban)
Thrombolysis (breaks down clots)
Embolectomy (if thrombolysis is contraindicated)
Inferior vena cava (IVC) filters
- if pt has recurrent DVTs despite anticoagulation or if anticoagulation is contraindicated
