Venous thromboembolism

what is thrombosis

• unwanted formation of a blood clot (thrombus), which can be arterial (in arterial system) or venous (in venous system)

• management approaches will differ depending on the location of the thrombus

what is arterial thrombus and venous thrombus

• arterial: composed of white thrombus, rich in platelets, leukocytes and fibrin

• venous: composed of red thrombus, has a small head and jelly-like tail

what is an embolism

• when a blood clot (thrombus) breaks away from its original site and travels elsewhere in the body

• travelling blood clot = embolus 

what is a venous thromboembolism 

• a blood clot (thrombus) that forms in the vein

• if the thrombus breaks off, the embolus can travel to the lungs → pulmonary embolism 

what is arterial thrombosis 

• thrombosis that occurs in arteries with fatty plaque → atherosclerotic site in the arterial system 

• compromised blood flow and oxygen in the artery → myocardial infarction or ischaemic stroke/TIA

what is intra-cardiac thrombosis

• thrombosis in the left atria or the heart valves 

• thrombus in heart can break off and move to other parts of the body, often to the brain, → ischaemic stroke/TIA

what is venous thrombosis

• thrombosis in the venous system

• original site is normally a vein in a leg → deep vein thrombosis

• can break off and travel (embolus), normally to the lungs → pulmonary embolism 

summary of venous thromboembolism

what is arterial thrombosis treated with and why

• antiplatelets 

• thrombus in atherosclerotic site of an artery (in either one of the coronary arteries or in the brain) → fatty plaque rupture → platelet activation and aggregation 

what is venous thrombosis treated with and why

• anticoagulants

• thrombus in venous site → inappropriate activation of the clotting cascade (platelets aren’t as involved)

• the thrombus that is formed have high fibrin and low platelet content

what is Virchow’s triad

the factors that he said contribute to thrombosis 

• venous stasis (slow bood flow )

• hypercoagulability (blood has an increased tendency to clot inappropriately)

• vessel-wall injury

what are the risk factors for VTE

• previous history of DVT or PE

• previous myocardial infarction 

• previous stroke 

• cancer 

• thrombophilia (blood has increased tendency to clot)

• immobility

• recent surgery (specifically pelvic region or legs)

• obesity 

• pregnancy 

• hormone replacement therapy 

what are the signs and symptoms of DVT

• unilateral leg pain (only one leg)

• swelling

• tenderness

• increased pressure 

• pitting oedema (swelling where pressure leaves a visible dent)

how is DVT diagnosed

• Doppler ultrasound → looks at blood flow abnormalities in the leg

• D-Dimer blood test → detects D-Dimer, which suggests a blood clot

how are D-Dimer fragments caused

• the blood clot is comprised mainly of fibrin, which holds it together 

• an enzyme called plasmin breaks the fibrin strands at both ends of the strand to produce two D units (D-Dimer fragments)

• presence of D-Dimer fragments not only suggest presence of a blood clot, as well as breakdown of the blood clot

what are the signs and symptoms of PE

• dyspnoea (shortness of breath)

• chest pain 

• dizziness, light-headedness

• tachycardia (HR more than 100bpm)

• tachypnoea (rapid breathing)

• haemoptysis (coughing blood)

what are the diagnostic tests for PE

• computed tomography pulmonary angiogram (CTPA) → taking a picture of the vessels between the heart and lungs)

• D-Dimer blood test 

what are the different treatment options for confirmed VTE

• anticoagulant therapy

  • parenteral anticoagulants → unfractionated heparin (UFH) or low-molecular weight heparin (LMWH)

  • oral anticoagulants → vitamin K antagonists (VKA) or non-vitamin K oral anticoagulants (NOAC/DOAC)

• thrombolytic therapy

  • for people with symptomatic iliofemoral DVT → clot formed in the iliac femoral vein

  • for people with PE and haemodynamic instability (concerning changes in BP or HR → higher risk of tissue perfusion issues)

• mechanical interventions 

  • insert inferior vena cava filter if anticoagulation is contraindicated

NICE guidelines for diagnosing DVT

• when person presents with symptoms, we take a clinical history and examination → start parenteral coagulation (LMWH) as it can get out of the system quickly if diagnosis is wrong

• 2-level DVT well score is then calculated to confirm a diagnosis

• a well score of 1 or less means DVT is unlikely → D-Dimer test done

  • negative test rules out a DVT and anticoagulation therapy is stopped

  • positive test → doppler ultrasound scan will be needed

• a well score of 2 or more means DVT is likely → doppler ultrasound is done within 4 hours

  • if it can’t be within 4 hours, D-Dimer test is done → scan is still done but within 24 hrs

  • positive scan → confirmed diagnosis

  • negative scan → look at D-Dimer test results

• if D-Dimer result is positive but the scan is negative → possibility of a DVT, but can’t be ruled out completely → stop anticoagulation + repeat the scan 6-8 days later

NICE guidelines for diagnosing PE

• when person presents with symptoms →  start parenteral coagulation 

• 2-level PE well score is then calculated to confirm a diagnosis

• a well score of 4 or less → means PE is unlikely → D-Dimer test 

  • negative test rules out PE and anticoagulation therapy is stopped 

  • positive test → CT pulmonary angiogram will be needed

• a well score of 4 or more means PE is likely → CT pulmonary angiogram is done immediately 

VTE management in different patient groups where long-term oral anticoagulation is needed after being discharged from hospital

• assess whether they show any signs of high bleeding risk e.g. anaemia, blood clotting disorders

  • full blood count

  • renal function and hepatic function 

  • Prothrombin Time and Activated Partial Thromboplastin Time

• first line treatment are usually DOACs e.g. apixaban 

  • they have greater acceptability with people

  • don’t require monitoring of INR

  • less interactions with other medicines and food

  • only one blood test is needed

  • monitoring is done annually

• DOACs are contraindicated in people with antiphospholipid syndrome as it leads to a higher occurrence of thrombotic events → use parenteral anticoagulant or VKA with warfarin 

• DOACs have different requirements e.g. to adjust dose depending on weight/renal function/age, to take at meal times etc