Thrombosis and Risk factors for thrombosis Flashcards
What are the 3 factors that contribute to increased risk of thrombosis (Virchow’s triad)?
- Change in blood flow (stasis)
- Change in blood composition (hyper coagulation)
- Damage to vascular endothelium
What is the primary pathological reason for arterial thrombosis?
Atherosclerotic plaque formation and rupture
- platelet aggregation and thrombi formation
- increased with obesity, hypertension, smoking, diabetes, family history, inactivity, male,, age
What are the main causes for venous thrombi?
Stasis - lack of flow due to venous damage/compression
Hyper coagulability - thrombi composed of FIBRIN rather than platelet aggregation/accumulation
How does venous thrombi present?
DVT - swelling, warm, painful to touch
What is the main complication of DVT?
Pulmonary embolism
What are the clinical presentations of PE?
Syncope
AF (new)
Cough - haemoptysis
What are the complications of venous thromboembolism?
- Sudden death
- Post thrombotic syndrome - chronic leg swelling, discomfort, ulceration
What is the definition of hospital acquired venous thromboembolism?
VTE within 90 days of discharge
What does the care pathway for venous thromboembolism comprise?
1 Assess risk for VTE
2 Assess bleeding risk (due to anti coagulant drugs being view)
3 VTE prophylaxis (mechanical/pharmaceutical depending on bleeding risk)
4 Assess risks
What are the risk factors for VTE?
- Cancer/treatment
- > 60yrs old
- Trauma/surgery
- Dehydration
- Thrombophilias (blood conditions)
- Comorbilities e.g. MI
- Immobility
- HRT/oestrogen
- History of VTE
- Family history of VTE
- Pregnancy
- Obesity (>30 BMI)
- Varicose veins
What comprise the pro-coagulant and anti-coagulant factors?
Procoagulant - platelets and clotting factors
Anticoagulant - protein C/S, AT-III, fibrinolytic system
What is the general advice for people at risk of VTE?
_ensure they are well hydrated
- ensure they are mobile asap
- Aspirin/other antiplatelts = not adequate prophylaxis
Name a mechanical form of VTE prophylaxis?
Compression stockings (increasing compression as you go down leg)
What are the pharmacological VTE prophylaxis?
Low dose low molecular weight heparin
Dabigatran - thrombin inhibitor
Apixaban - factor X inhibitor
Fondaparinox - antiXa inhibitor
How does heparin induce its effects?
Activates Antithrombin or inhibits Xa (different ways)
What does fractionated heparin do?
Blocks Xa and binds to antithrombin (stimulates) in equal amounts
What does low molecular weight heparin do?
Binds to both anti Xa and antithrombin but confers more an anti Xa effect
Whats does fondapprinux do?
Only binds to anti Xa activity
What does dabigatran/ apixaban do?
Bind factor X and thrombin directly
What are D-dimers? What are they used for?
Products of fibrin breakdown by plasmin
Elevated D-dimers = fibrin clots have formed and plasmin has broken then down - therefore, exclusion
What exclusion tests for PE/DVT are performed?
Wells score
What is a useful way to diagnose DVT
CT scan/Ultrasound
What is the treatment for DVT/PE?
Low molecular weight heparin then warfarin (overlap)
- Dabigatran (inhibits thrombin)
- apixaban (inhibits factor X)
- Fondaparinux (anti Xa)
Whats is the management for VTE (recurrent)?
Warfarin
If because of pregnancy, only temporary so do not consider warfarin
What is a thrombopilia?
Acquired/congenital condition of haemostasis mechanism that predisposes individual to thrombosis
Name some INHERITED thrombophilia conditions
Protein C/S deficiency
Anti thrombin deficiency
Factor V Leiden
Prothrombin 20210A
Name an ACQUIRED thrombophilia condition
Antiphospholipid
What are the clinical features of thrombophilias?
- DVT
- PE
- Thrombosis in axillary, portal, cerebral and mesenteric veins
What is the function of antithrombin?
Xa and thrombin inhibitor
What is the function of protein C? how is it activated?
Thrombin binding to thrombomodulin on endothelium
- complex activates protein C
- anticoagulant (balances coagulant-anticoagulation)
What is the function of protein S?
Cofactor of protein C -functions to break down factors 5 and 8 by proteolysis
How is protein C/S deficiencies inherited?
Autosomal dominant (50% chance of inheriting in parent = sufferer)
What is factor V leiden?
Factor V resistance to protein C cleavage
What does prothrombin 20210A do?
Point mutation
Increases prothrombin levels
