6. Thrombotic Disorders Flashcards
Define thrombosis
- pathological formation of an intravascular blood clot
- usually attached to the wall of the vessel
Define Embolism
Clot breaks off into the circulation
Lodges
Occludes distant vessel
What are the functions of the endothelium?
Barrier
Regulates fluid in tissues
Controls inflammation
Anticoagulant surface - thrombomodulin, activated protein C receptor
What is virchow’s triad?
Hypercoagulability
Stasis
Endothelial injury
What happens in the LA in AF?
Turbulence in the left atrial appendage
Clot can form which can break off and lodge somewhere in the body
Occurs more commonly in AF due to irregularly irregular pulse
What can cause hypercoagulability?
- Cancer - esp pancreas, lung, brain, gastric
- oestrogen- pregnancy, post-partum , COCP
- Antiphospholipid syndrome - found in SLE – anti-b2-GP1-antibody
- hereditary thrombophilia
- Factor V Leiden - unstable fV = more clottable
- ATIII deficiency
- Protein C and S deficiency
- Prothrombin mutation
What would you see in a DVT?
- Pain swelling sometimes erythema warmth shiny skin
- Lots of collaterals in the leg veins but occlusion in the larger pelvic or thigh veins is harder to bypass
- Diagnose with a duplex ultrasound if a vein is non-compressible then it is thrombosed
Where else may there be a venous thrombosis?
- in upper limb - rare. Usually iatrogenic due to lines, but may be cancer related
- Portal vein thrombosis - may cause abdo pain and swelling. Can lead to portal hypertension and therefore oesophageal varicies
- Central venous sinus thrombosis - rare, after pregnancy. Headache, blurry vision “venous stroke”
What causes a VTE/PE?
Unless there is a shunt, systemic venous blood must go through the lungs
Therefore when a large thrombus breaks off in a vein, the first small vessel it will lodge in is pulmonary artery
This leads to physiological dead space, where there is ventilation, but no perfusion of the blocked area
What are the signs and symptoms of PE?
Small ones
- symptoms = dyspnoea, pleuritic pain, haemoptysis
- Signs = tachycardia, tachypnoea, maybe pleural effusion signs
Larger
- fatal
- symptoms = syncope, pre-syncope, chest pain, dyspnoea
- signs = those of right heart strain
Why do you see RHF signs in PE?
RV has it easy throughout life
Not much resistance, as it is usually through the lungs
However, as soon as there is PE, it has to work harder
RV dilates, the more occlusion, the more it dilates
Leads to a downward spiral which leads to death
What is the treatment for vte?
Anticoagulation to prevent further VTE - give natural fibrinolytic enzymes a chance to clear the clot
Need to weigh up risks/benefits for each individual- risk of recurrent VTE vs risk of bleeding on treatment
What arterial thromboembolisms can occur?
- Arterial thrombosis - ruptured plaque lodges in end artery
- Acute limb ischaemia - clinical emergency. Thrombosis from ruptured atheroma in leg artery, or embolus from RA in AF
- Acute mesenteric ischaemia - more often embolic, but can be thrombotic in mesenteric artery. Diffuse, generalised abdominal pain, usually with N and V
- Stroke - primary thrombotic from atheroma rupture in supplying artery. Or embolic (big worry in AF)
What is paradoxical embolism?
DVT leads to a stroke
- patent foramen ovale, DVT can potentially embolise and go through the RA to LA, and out into arterial circulation
What disorders are associated with an increased risk of clotting?
Arterial
- Conditions and factors linked to atheroma
- Conditions and factors linked to AF
Venous
- very high risk - lower limb fracture, hip/knee surgery, major trauma, previous VTE, recent MI/HF
- moderate - chemo, cancer, AI disease, oestrogen, infarction
- weak - obesity, DM, age, pregnancy
