Thrombotic Disorders Flashcards
What are the elements of haemostasis?
- Primary haemostasis
- Blood coagulation
- Fibrinolysis
What is involved in primary haemostasis?
- Vasoconstriction
- Platelet adhesion
- Platelet aggregation
What is involved in coagulation?
- Insoluble fibrin formation
- Fibrin cross-linking
How does fibrinolysis take place?
- Urokinase, tPA (tissue plasminogen activator) and factor XII convert plasminogen to plasmin
- Plasmin converts fibrin to fibrinogen/fibrin degradation products
What is a thrombus?
A clot arising in the wrong place
What is a thromboembolism?
Movement of clot along a vessel
What is Virchow’s triad?
These factors increase risk of thrombosis:
- Stasis
- Hypercoagulability
- Vessel damage
What contributes to stasis?
- Bed rest
- Travel
What contributes to vessel damage?
Atherosclerosis
What contributes to hypercoagulability?
- Pregnancy
- Combined pill or HRT
- Trauma
What are the 3 types of thrombosis?
- Arterial
- Venous
- Microvascular
What is an arterial clot formed of?
White clot = platelets and fibrin
What do arterial clots result in?
Ischaemia and infarction
What are arterial clots usually secondary to?
Atherosclerosis
Give examples of arterial thromboembolism.
- Coronary thrombosis
- MI
- Unstable angina
- Cerebrovascular thromboembolism
- Stroke
- Transient ischaemia
- Peripheral embolism
- Limb ischaemia
What are the risk factors for arterial thrombosis?
- Age
- Smoking
- Sedentary lifestyle
- Hypertension
- Diabetes mellitus
- Obesity
- Hypercholesterolaemia
How is arterial thrombosis managed?
- Primary prevention
- Lifestyle modification
- Treatment of vascular risk factors
- Acute presentation
- Thrombolysis
- Antiplatelet/anticoagulant drugs
- Secondary prevention
What are venous thrombi formed of?
Red thrombus = fibrin and RBC
What does venous thrombosis result in?
Back pressure in venous system (eg swollen red leg)
What is venous thrombosis principally due to?
Stasis and hypercoagulability
Give examples of venous thromboembolism.
- Limb deep vein thrombosis
- Pulmonary embolism
- Visceral venous thrombosis
- Intracranial venous thrombosis
- Superficial thrombophlebitis
What are the risk factors for venous thrombosis (stasis and hypercoagulability)?
- Increasing age
- Pregnancy
- Hormonal therapy (COCT/HRT)
- Tissue trauma (including surgery)
- Immobility
- Obesity
- Systemic disease
- Family history
What systemic diseases are associated with increased risk of venous thrombosis?
- Cancer
- Myeloproliferative neoplasm
- Autoimmune disease
- Inflammatory bowel disease
- Connective tissue disease e.g SLE
- Antiphospholipid syndrome: arterial and venous thrombosis
How is venous thrombosis diagnosed?
- Pretest probability scoring
- Wells score
- Geneva score
- Lab test if probability low
- D-dimer
- If Thrombosis likely then go straight to Imaging
- Doppler US
- V/Q scan (chest X ray done first to exclude other causes of chest symtoms)
- CT pulmonary angiogram (gold standard when investigating for PE. Gives anatomical information.)
What is the aim of management in venous thrombosis?
- Prevent clot extension
- Prevent clot embolisation
- Prevent clot recurrence in long term treatment
What drugs can be given for venous thrombosis?
Anticoagulants (for 3 months or long term)
- LMWH (can be used in pregnancy and for cancer associated thrombosis) -
- Coumarins (warfarin)
- DOACs
- Thrombolysis only in selected cases
- Massive PE
Heritable thrombophilia
An inherited predisposition to venous thrombosis
Give examples of common heritable thrombophilia’s.
- Factor V Leiden
- Prothrombin G20210A
Give examples of rare heritable thrombophilias.
- Antithrombin deficiency
- Protein C deficiency
- Protein S deficiency
What is the clinical utility of screening for heritable thrombophilias?
- Majority are not predictive of recurrent event
- Screening of asymptomatic family members not recommended
- Limited thrombophilia screening: restricted to high risk heritable thrombophilia (antithrombin deficiency)
What are microvascular clots formed of?
Platelets and/or fibrin
What does microvascular thrombus result in?
Diffuse ischaemia
What does microvascular thrombus principally occur in?
Disseminated Intravascular Coagulation (DIC)
What is DIC?
Diffuse systemic coagulation activation
What does DIC occur in?
- Septicaemia
- Malignancy
- Eclampsia
What does DIC cause?
- Gangrene
- Organ failure
What causes bleeding in DIC?
Consumption of platelets and clotting factors leads to bleeding
Management of DIC
Low dose anticoagulant (Most deaths are caused by microvascular thrombosis rather than bleeding)
