Thrombotic Disorders Flashcards
What are the 2 pathways involved in fibrinolysis and what are the activators/enzymes involved?
Extrinsic pathway - Tissue Plasminogen activator (TPA)
Intrinsic pathway - Factor XII
What do TPA and Factor XII react with in order to create plasmin?
Plasminogen
What does plasmin react with in order to create fibrinogen and fibrinogen breakdown products (e.g D-dimer)?
Fibrin
Draw a simplified version of the fibrinolysis pathway
What is a thrombus?
A clot arising in the wrong place
What is meant by the term thromboembolism?
Movement of a clot along a vessel
Draw Virchows Triad
What can cause problems with each component of Virchows Triad?
Stasis - Bed rest or Travel
Vessel Damage - Atherosclerosis
Hypercoagulability - Pregnancy or Trauma
What are the 3 locations in which thrombosis can occur?
1 - Arterial
2 - Venous
3 - Microvasculature
What is the most likely primary cause of an arterial thrombus?
Atherosclerosis
What are consequences of an arterial thrombus?
Ischaemia
Infarction
What are the most common types of arterial thromboembolism?
1) Coronary Thromboembolism
2) Cerebrovascular Thromboembolism
3) Peripheral Embolism
What conditions can occur due to a coronary thromboembolism?
MI
Unstable angina
What conditions can occur due to a cerebrovascular thromboembolism?
1) Stroke
2) TIA
What conditions can occur due to a peripheral thromboembolism?
1) Limb Ischaemia
What are the risk factors for arterial thromboembolism?
1) Smoking
2) Age
3) Sedentary lifestyle
4) Hypertension
5) Obesity
6) Diabetes Mellitus
7) High cholesterol
How are arterial thromboemboli’ primarily prevented?
1 - Lifestyle modification
2 - Treatment of vascular risk factors
How are arterial thromboemobli managed in an acute presentation?
1) Thrombolysis
2) Antiplatelet (aspirin/ticagrelor)/anticoagulant (warfarin/LMWH) drugs
What are the constituents of an arterial thrombus?
Platelets
Fibrin
What are the constituents of venous thrombus?
Red cells
Fibrin
What is the main physiological effect of venous thrombi’?
Back pressure
Thinking of Virchows Triad, what are the main causes of venous thrombus’?
Stasis
Hypercoagulability
What are the most common types of venous thromboembolism?
Deep vein thrombosus
Pulmonary embolism
What factors can affect stasis and hypercoagulability that both contribute to venous thromboembolisms?
1 - Immobility
2 - Surgery
3 - Obesity
4 - Pregnancy
5 - COCP/HRT
6 - Increasing age
What systemic diseases are associated with an increased risk of venous thrombosis?
1 - Cancer
2 - Myeloproliferative Neoplasm
3 - Inflammatory bowel disease
4 - SLE
What are the 2 pretest scoring methods used to indicate the likelihood of a venous thrombosis?
1 - Wells score
2 - Geneva score
Which pretest scoring method is best for diagnosing DVT’s?
Wells score
Which pretest scoring method is best for diagnosing PE’s?
Geneva score
What lab testing will be performed if the pretest probability score was low?
D-dimer
What sensitivity and specificity does the D-dimer test have?
Highly sensitive
Not specific
If the D-dimer result is low, what is the next step?
Imaging
If the pretest probability score is high, what would be the next step?
Imaging
No need for D-dimer test
What imaging modalities are used to diagnose venous thromboembolisms?
Compression Doppler USS
V/Q perfusion scan
CT Pulmonary Angiogram
What would be the features of a DVT on compresison doppler USS?
1 - Thrombosed vein enlarged
2 - Thrombosed vein non-compressible
What are the features of a PE on a V/Q perfusion scan?
Mismatch between perfusion and ventilation
What scan must be performed before doing a V/Q perfusion scan?
The patient must have a normal X-ray scan
What is the gold standard imaging method for PE’s?
CT Pulmonary Angiogram
What are the aims of management of DVT’s/PE’s?
1 - Prevent clot extension
2 - Prevent clot embolisation
3 - Prevent clot recurrence in long term
What are the anticoagulant drugs used to treat DVT/PE’s?
Anticoagulants - Warfarin, LMWH or DOAC’s
Thrombolysis for massive PE’s
What are the most common heritable thrombophilias?
1 - Factor V Leiden
2 - Prothrombin G202
What does Factor V Leiden cause?
An increase in clotting, i.e. a hypercoagulable state
What protein is affected by Factor V Leiden mutation?
Protein C
To which group of patients is thrombophilia screening useful?
Antithrombin deficiency
What sort of ischaemia is present with microvascular thrombus?
Diffuse ischaemia
In what condition are microvascular thrombus’ most common?
Disseminated Intravascular Coagulation (DIC)
In what conditions is DIC most commonly seen?
1 - Septicaemia
2 - Malignancy
3 - Eclampsia
