Clinical aspects of thrombosis Flashcards
What is thrombosis?
Inappropriate blood coagulation within a vessel
When does appropriate blood coagulation occur?
When blood escapes from a vessel
What are the types of thrombosis?
In the arterial circulation:
- High pressure system
- Platelet rich
In the venous circulation:
- Low pressure system
- Fibrin rich
What can arterial thrombosis cause?
MII
Thrombotic stroke
When can venous thrombosis cause?
Leg deep vein thrombosis (MI) Pulmonary embolism (PE)
How to treat thrombosis?
Arterial thrombosis - anti-platelet drugs
Venous thrombosis - anticoagulant thrombosis
How does arterial thrombosis form?
Atherosclerotic plaque:
- Initial fatty streak
- Plaque enlargement
- Turbulence due to protrusion into lumen
- Loss of endothelium and collagen exposure
- Platelet activation and adherence
- Fibrin meshwork deposotion and red cell entrapment
- More turbulence, more platelet and fibrin deposition
- Thrombus of layers of platelets, fibrin and red cells
Risk factors for arterial thrombosis?
Main risk factors: Family history Diabetes mellitus Hypertension Hyperlipidaemia Smoking Atrial fibrillation for stroke
Other risk factors: Male sex Polycythaemia, gout Collagen vascular disease Lupus anticoagulant, high FVIII, high fibrinogen
How to manage arterial thrombosis?
Lifestyle: Quit smoking Exercise Diet Weight control
Antithrombotics: primary prevention in pts with atrial fibrillation
Treatment options for arterial thrombosis?
Antiplatelet agents: start acutely, continue long term
Aspirin:
Irreversible inhibitor of cyclooxygenase (COX1), inhibiting the production of thromboxane.
Inhibition lasts for the lifespan of platelet: ≈ 1 week.
Risk reduction of non fatal vascular event by 30%.
Risk reduction of fatal vascular event by 15%.
Dose: 75-300mg/day
Clopidogrel:
Irreversible ADP mediated platelet inhibition.
Inhibition lasts for the lifespan of platelet: ≈ 1 week.
Decreases the risk of MI 18%,
Risk of coronary stent thrombosis/recurrent stroke by 30%.
Dose 75mg/day
Thrombolysis
Indications:
MI, stroke within 3 hours, life-threatening PE
Drugs:
ALTEPLASE (rt-PA, tissue-type plasminogen activator)
STREPTOKINASE
Main side effect: bleeding
Invasive
Percutaneous coronary intervention (cardiac stenting)
Combined with 3 – 12 months aspirin + clopidogrel
Coronary artery bypass grafting
Carotid endarterectomy
Rehabilitation in all cases
Stroke: swallowing, malnutrition, mobilisation
Secondary prevention of arterial thrombosis (treatment)?
Lifestyle - Exercise, stop smoking, diet, weight control, safe alcohol use.
Blood pressure control
Cholesterol lowering
Diabetic control
Antithrombotic therapy in stroke associated with atrial fibrillation
What is atrial fibrillation?
Irregular heart rhythm
Embolisation leads to stroke
Impaired cardiac output
Treatment of atrial fibrillation?
DC cardioversion
HR control: B blockers, Ca channel blocker, digoxin, AV junction ablation
Anticoagulation
How does atrial fibrillation cause stroke?
- Blood pools in atria
- Blood clot forms
- Blood clot breaks off
- Blood clot travels to brain and blocks a cerebral artery causing a stroke
What can a deep vein thrombosis cause?
Pulmonary embolism = death OR pulmonary hypertension = chronic PE = death
Deep vein insufficiency = post-thrombotic syndrome = leg ulcers
How does a venous thrombosis form? (what are the risk factors)
Hypercoagulability - inherited, acquired
Vascular damage - acquired
Stasis - acquired
Risk factors of venous thrombosis?
Heritable:
- Antithrombin deficiency
- Protein C deficiency
- Factor V Leiden
- Prothrombin mutation 20210 A
Acquired:
- Age
- Previous VTE
- Antiphospholipid syndrome
- Paralysis
- Major trauma
- Pregnancy
- Chemo
- Obesity
- Contraceptive pill
Mixed:
- Raised FVIII
- Raised FIX
- Raised XI
- Raised fibrinogen
Heritable thrombophilias
TABLE…. SLide 21
List the types of heritable thrombophilias?
Factor V Leiden Prothrombin gene mutation Protein C deficiency Protein S deficiency Antithrombin deficiency
Name the most common heritable thrombophilia
Factor V leiden
What is the incidence of venous thrombosis?
50% of pts with a strong family history have heritable thrombophilia - thrombophilic defect is identifiable
1 in 1000 overall
Higher in older age
3 in 10.000 age 40
26 in 10.000 age 80
How to prevent a venous thrombosis?
Adequate hydration
Early mobilisation
Mechanical prophylaxis:
All surgical patients at risk of VTE
Graduated elastic compression hosiery
Intermittent pneumatic compression (flowtron boots or foot pumps).
Chemical prophylaxis prevents 50 – 70% of VTE:
- Low molecular weight heparin
- Direct oral anticoagulants
Risk assessment of VTE and dental surgery - what to do?
Do not routinely offer pharmacological or mechanical VTE prophylaxis to pts undergoing a surgical procedure with LA by infiltration with no limitation of mobility
Risk assess on admin and reassessed within 24hrs
VTE treatment?
Acute: - Anticoagulation - Thrombolysis - Thrombectomy Inferior vena cava filter
Long term:
- Anticoagulation
- Stockings
