Thrombotic events Flashcards
(33 cards)
What are the types of thrombotic events?
Arterial
- Coronary, cerebral, peripheral
Venous
- Deep venous thromboses
- Pulmonary Embolism
What is arterial thrombosis?
A blood clot which forms in the artery.
Risk factors for arterial thrombosis?
Factors that can cause damage to the endothelium, increase in foamy macrophages and platelet activation:
- Hypertension
- Smoking
- High cholesterol
- Diabetes mellitus
What is the pathophysiology of atherosclerosis?
Damage to endothelium causes recruitment of “foamy” macrophages rich in cholesterol, resulting in the formation of cholesterol-rich plaques.
STABLE plaques result in stable angina and intermittent claudication.
UNSTABLE plaques result in stroke, unstable angina or myocardial infarction.
- Plaques rupture, platelets are recruited and cause acute thrombosis leading to sudden symptom onset.
- Leads to acute organ ischemia and infarction
Pathophysiology of platelets in arterial thrombosis?
- Plaque ruptures - more likely in the high pressure environment of the arteries.
- Exposed endothelium and release of Von Willebrand factor and other proteins for which platelets have receptors for leads to platelet adhesion to the site of injury.
- Platelets become activated - releases granules that activate coagulation and recruit other platelets to develop a platelet plug (e.g. ADP, thrombin and thromboxane A2).
- Platelet aggregation via membrane glycoproteins (fibrinogen)
Management of arterial thrombosis?
Basic principles of management:
- Aspirin and other anti-platelet drugs
- Modify risk factors for atherosclerosis
- Stop smoking, treat hypertension, treat diabetes and lower cholesterol.
What is deep vein thrombosis?
Refers to the intra-luminal occlusion of any vein within the deep system of a limb (either arm or leg) or the pelvis
Aetiology of venous thrombosis?
Venous thrombosis is considered to arise from the interplay between the three factors that make up Virchow’s triad
What are the components of Virchow’s triad?
Hypercoagulable state
Endothelial injury
Circulatory stasis
What are all the causes of hypercoagulable states?
- Malignancy
- Pregnancy and peripartum
- Oestrogen therapy
- IBD
- Sepsis
- Thrombophilia (abnormal tendancy to form blood clots)
What are all the causes of endothelial injury?
- Venous disorders
- Venous valvular damage (e.g. from previous DVT/PE - very strong RF)
- Trauma or surgery
- Indwelling catheters
What are all the causes of circulatory stasis?
- Left ventricular dysfunction
- Immobility or paralysis
- Venous insufficiency/varicose veins
- Venous obstruction - tumour, obesity, pregnancy
Pathophysiology of venous thrombosis?
The venous system is a low pressure system so platelets are not activated, this activates coagulation cascade which leads to clot rich in fibrin
What is the difference between DVT and PVT?
- Distal vein thrombosis: refers to DVT of the calves
- Proximal vein thrombosis: DVT of the popliteal or femoral vein, more likely to embolise
Symptoms for venous thrombosis?
- Calf - warmth, tenderness, swelling, erythema (unilateral)
- Mild fever
Signs of venous thrombosis?
- Pitting oedema
- Pain on palpation of deep veins
- Distention of superficial veins
Investigations for venous thrombosis?
- D-dimer: rule out test for patients considered unlikely to have a DVT based on the Wells score
- US Doppler leg scan: diagnostic, indicated if patient has raised D-dimers, or if they have a Wells score of 2 or more (in which case US would be first line)
Acute management for venous thrombosis?
- Anticoagulation: apixaban or rivaroxaban (DOACs) first line
- May be outpatient if patient considered low-risk
- If neither apixaban or rivaroxaban are suitable then either LMWH followed by dabigatran or edoxaban
OR LMWH followed by a vitamin K antagonist (i.e. warfarin)
- Percutaneous mechanical thrombectomy: used in massive DVTs
- IVC filter: does not actually treat the DVT but reduces the risk DVT embolising into the pulmonary arteries causing a PE, used in patients where anticoagulation is contraindicated
What type of drug is warfarin?
Vitamin K antagonist
Secondary prevention of venous thrombosis?
- The options for long term anticoagulation are warfarin, a DOAC or LMWH
- Treatment with a should be continued for at least three months
- Provoked DVT with reversible factors - 3 months
- Provoked DVT with irreversible factors, or unprovoked DVT - 3-6 months, potentially life-long depending on patient factors (e.g. genetic clotting disorder)
What are hereditary thrombophilias?
A group of genetic defects in which affected individuals have an increased tendancy to develop premature, unusual and recurrent thromboses
Aetiology of hereditary thrombophilias?
- Factor V Leiden
- Prothrombin 20210 mutation
- Antithrombin deficiency
- Protein C deficiency
- Protein S deficiency
Are there any symptoms with hereditary thrombophilias?
Usually does not have any symptoms, only becomes apparent when patient develops a thrombosis
When should a hereditary thrombophilia screening be considered?
- Venous thrombosis <45 years old
- Recurrent venous thrombosis
- Unusual venous thrombosis
- Family history of venous thrombosis
- Family history of thrombophilia
