Thombosis Flashcards
what are the two types of thrombotic events
Arterial
- Coronary, cerebral, peripheral
Venous
- DVT or PE
how does the venous system and the arterial system differ
arterial system
- much thicker, much higher pressure system
venous
- thinner, lower pressure, valves, platelets don’t get activated
what causes an arterial thrombosis
Atherosclerosis - damage to the epithelium, cholesterol plaque, it rupture, platelets stick to it, can lead to occluding the vessel
Therefore, a Platelet rich thrombus
what is the Tx for an arterial thrombosis
Aspirin or Clopidogrel
Modify risk factors for atherosclerosis
what is activated in a venous thrombosis
coagulation cascade i.e. fibrin clot
platelets not activated
what dysfunction in what triad leads to a venous thrombosis
think Virchow’s triad
- stasis
- vessel wall
- hypercoagulability
what is the Tx for a venous thrombosis
heparin/warfarin/
other new oral anticoagulants
going after secondary haemostasis
what are risk factors for a venous thromboembolism
Age Obesity Pregnancy Puerperium - the 6 weeks after child birth Oestrogen therapy Previous DVT/PE Trauma/surgery Malignancy Paralysis Thrombophilia
why is pregnancy a risk factor for venous thromboembolism
clotting factors raise to about 3 times normal to prepare for childbirth to try stop bleeding
Age, Pregnancy, Puerperium, Oestrogen therapy, Trauma/surgery, Malignancy and infection are associated with Hypercoagulability - why does this increase the risk of a venous thromboembolism
they are all associated with the release of tissue factor, raised vWF and factor 8.
what is thrombophilia
Familial or acquired disorders of the haemostatic mechanism which are likely to predispose to thrombosis.
what are potential mechanisms for thrombophilia
increased coagulation activity
decreased fibrinolytic activity
decreased anti-coagulant activity
what are potential reasons for a decreased anti-coagulant activity
low levels of anti-thrombin III
low levels of protein C and S
what is the commonest cause for a decreased anti-coagulant activity
factor V leiden
- varient in factor V gene, makes it more difficult for protein C and S to switch it off
what are examples of HEREDITARY thrombophilia
Factor V Leiden Prothrombin 20210 mutation Antithrombin deficiency Protein C deficiency Protein S deficiency
when should hereditary thombophilia screening be considered
Venous thrombosis <45 years old Recurrent venous thrombosis Unusual venous thrombosis Family history of venous thrombosis Family history of thrombophilia
Mx of hereditary thombophilia
Advice on avoiding risk
Short term prophylaxis
Short term anticoagulation
- treat episodes
Long term anticoagulation
- if recurrent thrombotic events
what is an example of an acquired thrombophilia
Antiphospholipid antibody syndrome
- more likely for thrombosis than hereditary thrombophilia
what is features of Antiphospholipid antibody syndrome
young women, autoimmune presenting with CLOT
Clotting [DVT, PE]
Livedo reticularis
Obstetric (recurrent misarriages)
Thrombocytopenia (decreased platelets)
what antibodies are seen in Antiphospholipid antibody syndrome
Anti-cardiolipin antibodies and lupus anti-coagulant.
Tx of Antiphospholipid antibody syndrome
Aspirin and Warfarin
due to activation of both primary and secondary haemostasis»_space; arterial and venous thrombosis
how does atherosclerosis occur
Damage to endothelium
Recruitment of ‘foamy’ macrophages rich in cholesterol
Forms plaques rich in cholesterol
Hyalinised and calcified»_space; arteries become hard
what are stable Atherosclerotic plaques
stable angina (coronary artery), intermittent claudication (leg artery)
what happens with an unstable Atherosclerotic plaque
Plaques rupture, platelets are recruited and cause acute thrombosis
Sudden onset of symptoms
Unstable angina or MI (coronary arteries)
Stroke (cerebral arteries)
what are risk factors for arterial thrombosis
Hypertension [damage to endothelium > platelet activation]
Smoking
High cholesterol
Diabetes
how is an arterial thrombosis prevented
Stop smoking Treat hypertension Treat diabetes Lower cholesterol Anti-platelet drugs
what chemicals do platelets secrete to recruit more platelets to the site i.e. activation
ADP
Thromboxane A2
how do platelets bind to sub endothelial collagen i.e. adhesion
Glycoprotein 1b and Von Willebrand Factor.
how to platelets attach to each i.e. aggregation
via fibrinogen and GPIIbIIIa
how does aspirin work
Inhibits cyclo-oxygenase [COX 1] which is necessary to produce Thromboxane A2
what are side effects of aspirin
- Bleeding
- Blocks production of prostaglandins:
- GI ulceration
- Bronchospasm
how does Clopidogrel and prasugrel work
ADP receptor antagonists
how does dipyridamole work
Phosphodiesterase inhibitor -reduces production of cAMP which is a ‘second messenger’ in platelet activation
how does abciximab work
GP IIb/IIIa inhibitors
- inhibit aggregation
how can serious bleeding in anti platelet therapy be reversed
platelet transfusion
what must happen prior to surgery is someone is on anti platelet therapy
stop anti-platelet agents 7 days prior
Sx and Signs of DVT
Unilateral
Pain
Swelling
Erythema
Sx and signs of PE
SOB
Pleuritic chest pain
Rub
Hypoxia
what is DVT prophylaxis and Tx
TED stockings
Physiotherapy
Early mobilisation
Heparin
Warfarin
