Thrombotic Disorders Flashcards
What are the elements of haemostasis?
Primary haemostasis - primary plug formation
Blood coagulation
Fibrinolysis
What are the elements of primary haemostasis?
Vasoconstriction mediated by substances e.g. catecholamines, nitric oxide, calcium
Platelet adhesion to damaged endothelium
Platelet aggregation
What is involved in coagulation?
Insoluble fibrin formation - fibrin cross linking
What is the end goal of haemostasis?
Fibrin production which leads to fibrinolytic pathways
What promotes the breakdown of plasminogen to plasma?
tPA and factor XII
What is a thrombus and what is a thromboembolism?
Thrombus is a clot arising in the wrong place, thromboembolism is the movement of a clot along a vessel
What are the elements of Virchow’s triad?
Stasis
Hypercoagulability
Vessel damage
What are the types of thrombosis?
Arterial
Venous
Microvascular
What are the features of venous thrombus?
Red thrombus - predominantly fibrin, also red cells
Results in back pressure
Principally due to stasis and hypercoagulability
What are the types of venous thromboembolism?
Deep vein thrombosis Pulmonary embolism Visceral venous thrombosis Intracranial venous thrombosis Superficial thrombophlebitis
What systemic diseases are associated with venous thrombosis?
Cancer - some patients present with VTE as first sign of malignancy
Myeloproliferative neoplasm e.g. polycythaemia
Autoimmune disease
- IBD
- connective tissue disease e.g. SLE
- anti-phospholipid syndrome
What should be considered in an unprovoked DVT/PE with no obvious trigger?
Occult malignancy
How is venous thrombosis diagnoses?
Pretest probability scoring - Wells score/Geneva score
Laboratory testing - D-dimer
Imaging
- doppler ultrasound
- ventilation/perfusion scan
- CTPA
When is it recommended to go straight to imaging investigation of venous thrombosis?
If pretest probability is high
What does it mean if the d-dimer is negative?
Essentially excludes VTE if negative
If positive it does not confirm VTE as it can go up in a number of other conditions, needs to be considered in appropriate clinical circumstances
What feature on doppler ultrasound should raise suspicion of a clot?
If vein is non-compressible
What are the aims of management of VTE?
Prevent clot extension
Prevent clot embolisation
Prevent clot recurrence in long-term treatment
What drug type breaks down clots?
Thombolytics promote fibrinolysis so break down clots, anticoagulants do not break down clots
What do anticoagulants do?
Do not break down the clot - work to prevent clot formation or prevent pre-existing clot from getting larger
What drugs are used in management of VTE?
Anticoagulants
- LMWS
- coumarins e.g. warfarin
- direct oral anticoagulants
Thrombolysis only in selected cases e.g. massive PE
What is heritable thrombophilia?
An inherited predisposition to venous thrombosis
What are the causes of heritable thrombophilia?
Common - mutation in factor V Leiden or prothrombin G20210A
Rare - anti-thrombin deficiency, protein C deficiency, protein S deficiency
What are the features of factor V Leiden mutation?
Results in factor Va
Va should be broken down by activated aPC but with the mutation it becomes resistant to this
Activated protein C and protein S should break down factor V and VIII to keep haemostatis balance but there is a block of breakdown of factor V in this mutation
What are the physiological anticoagulants?
Protein C and S
If these are mutated, natural anticoagulation will not occur so predisposition to VTE occurs
