Lecture 21 - Thrombosis Flashcards Preview

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Flashcards in Lecture 21 - Thrombosis Deck (20)
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Common sites of thrombosis

- arterial: coronary artery (MI), cerebral artery (stroke), femoral artery (peripheral vascular disease)
- Venous: pelvic, leg veins (DVT), Pulmonary artery (PE), hepatic, portal v (Veno-occlusive disease), cerebral vein (sinus thrombosis)
- other sites: heart valves: bacterial endocarditis
- multiple DIC


Arterial thrombosis

- atherosclerosis
- endothelial disruption
- platelet activation

- forms a platelet rich WHITE thrombus


Risk factors for arterial thrombosis

- Major: age, male, race,family hx, hyperlipidemia, hypertension, smoking, diabetes mellitus

- Minor: obesity, physical inactivity, stress/personality, other dietary factors, oestrogen deficiency, lipoprotein profiles, homocysteine


Atherosclerosis triggers arterial thrombosis

- normal vessel -> fatty streak -> fibrous plaque/calcification/hemorrhage -> plaque rupture, thrombosis


Therapy of arterial thromboembolism

- Aspirin: and/or other antiplatelet agents for threatened occlusion, improves survival after MI
- Heparin - unstable angina
- thrombolysis: streptokinase, tPA used acutely in MI, local urokinase in peripheral arterial occlusion
- warfarin: only after initial heparin therapy, used for long term prophylaxis, prevention


Antiplatelet agents

- COX inhibitors: aspirin, NSAID, Cox1/2
- phosphodiesterase inhibitors: dipyridamole
- ADP receptor inhibitors: clopidogrel
- GPIIb-IIIa antagonists: abciximab, tirofiban
- others: Serotonin antagonist, PAF antagonist
- newer agents are often more potent than aspirin but are more toxic and expensive


Venous thrombosis

- Venous obstruction
- impaired flow - stasis
- coagulation factor activation
- forms an erythrocyte-rich RED thrombus



- about 50% of patients with proximal DVT of the lef have asymptomatic PE
- DVT is found in around 80% of patients with PE (mainly asymptomatic)


Diagnosis of VTE

- most are clinically silent, proximal or distal
- 1cm
- differential Dx: MSK problems, impaired venous and lymphatic outflow, popliteal inflammatory Baker's cyst
- clinical suspicion mandates confirmation


Superficial thrombophlebitis

- saphenous veins, varicose veins, IV catheters, migratory superficial thrombophlebitis
- trousseau' sign - carcinoma
- tender cord, erythema, oedema
- low embolic risk


Diagnostic techniques

- ascending phlebography: contrast induced thrombosis of peripheral veins 2-3%, cost, time consuming
- duplex ultrasonography: symptomatic proximal DVT: sensitivity 93%, specificity 98%. Much lower sensitivity for detection of distal thrombu and in screening of asymptomatic patients


Upper limb thrombosis

- 1-2% of all DVT
- pain, swelling of upper extremity
- effort or exercise induced: hyperabduction, external rotation
- trauma to axillary or subclavian vein, absent in 13-32%
- thoracic outlet syndrome: first rib, fibromuscular band, clavicle, muscle hypertrophy
- central venous access devices


Risk factor for venous thrombosis

- prior history of VTE
- malignancy
- immobilisation
- heart failure
- pregnancy, OCP, HRT
- inherited prothrombotic factor
- age, obesity
- antiphospholipid antibodies: LA, ACA
- dehydration
- infection, indwelling central venous catheters


Post thrombotic syndrome

- chronic complication of DVT, 1/3 pts, severe in 5-10%
- clinical diagnosis: symptoms intermittent or persistent, aggravated by standing or walking, relieved by rest and elevation, aching, heaviness swelling cramps, itching and tingling
- signs: oedema, permalleolar telangiectasia, brown pigmentation, venous eczema, secondary varicose vein, ulceration


Post thrombotic syndrome

- risk factors: persistent LL symptoms, anatomically extensive DVT, recurrent extensive DVT, recurrent ipsilateral DVT, obesity, advanced age

- treatment: compressions


Thrombosis and travel

- long duration of travel is weak risk factor for VTE
- severe symptomatic PE: rare in flights
- VTE may be attributed to travel for 8 weeks after journey
- risk is greatest in individuals with preexisting risk factor VTE
- dehydration is not a risk factor but evidence that maintaining mobility may prevent VTE


Who should be on SC heparin injection

- those with previous travel-associated thrombosis
- those with previous spontaneous PE
- those with past thrombosis and multiple risk factor


Prevention of venous thrombosis

- mobilisation
- calf compression
- hydration
- LMWH short term or warfarin long term for those at risk


- is aspirin effective prophylaxis against venous thrombosis

- No
- bleeding can be a problem



- Subcutaneous administration
- predictable anticoagulant effect - no monitoring
- less bleeding
- potential for reversibility