PP 5 Thrombosis + Embolism Flashcards
Thrombosis defintion
Formation of solid mass of blood within the circulatory system
Thrombus definition
Solid mass of blood within circulatory system
Clot defintion
Mass of blood outside vessel wall
Thrombus vs clot
Thrombus is within circulatory system
Clot is outside circulatory system
What is Virchow’s triad?
Thrombus form when there’s abnormalities in:
- vascular wall
- blood flow
- blood components
What can cause damage to vascular system?
Atheroma
Inflammation - vasculitis
Direct injury
Damage to heart
Atheroma definition
Degeneration of arteries due to fatty deposition
What causes change to blood flow?
Stasis
Turbulent blood flow
Stasis in blood meaning
Slowing of blood
Causes of blood stasis
Narrowing of vessels
Low BP
Immobility
Causes of turbulent blood flow
Defects in walls + heart valves
Atrial fibrillation
Hypercoagulable state of blood meaning
Sticky blood
Who is at risk of hypercoagulable blood?
Smokers
Pregnancy + post-partum
Trauma + burns
Post-operative patients
Genetic diseases e.g anti thrombin III deficiency
Appearance of an atrial thrombus
Pale
Granular
Lower cell content
Lines of Zahn
Appearance of a venous thrombus
Deep red
Soft
Gelatinous
Higher cell content
Why are lines of Zahn present in arterial thrombi but not venous?
There is a degree of shielding by valves in veins
Describe the formation of thrombus
1- platelets are activated
2- platelets aggregate + bind together by fibrin
3- RBCs get trapped
4- thrombus formed
Role of plasmin
Degrades fibrin
Dissolves thrombus
What is a breakdown product of fibrin?
D-dimers
What can D-diners be detected in the blood for?
Indicate clotting occurring
What converts plasminogen to plasmin/
tPA tissue plasminogen activator
What breaksdown fibrin?
Plasmin
List possible outcomes of thrombosis
Lysis
Propagation
Organisation
Recanalisation
Embolism
What process restores complete blood flow after thrombosis?
Lysis
What is lysis of thrombosis?
Breakdown of thrombus
What type thrombi does lysis occur to?
Small ones
What is propagation of thrombus?
Spread of thrombosis
What is organisation of thrombus?
In growth of fibroblasts + capillaries
Lumen remains obstructed
What is recanalisation of thrombus?
Channel formation through an organised thrombus
What process restores partial blood flow after a thrombus?
Recanalisation
What is embolism of a thrombus?
Part of thrombus breaks off
Travels in bloodstream
Lodges at distant site
Effects of venous thrombosis
Congestion
Oedema
Ischaemia
Infarction
Common locations of venous thrombosis
Cavernous sinus
Subclavian vein
Inferior vena cava
Uteroplacental
Deep vein thrombosis
Effects of arterial thrombosis
Ischaemia
Infarction
Dependent on site + collateral blood supply
Common locations of arterial thrombosis
Cerebral artery
Carotid artery
Coronary artery
Mesenteric + renal artery
Femoral, iliac + popliteal artery
What can thrombosis in cerebral artery cause?
Ischaemic stroke
What can thrombosis in coronary artery cause?
Myocardial infarction
Embolism definition
Blockage of blood vessel by solid, liquid or gas at distant site room organ
Examples of embolisms
Thrombus
Air
Amniotic fluid
Nitrogen
Medical equipment
Fat
Tumour cells
List come predisposing factors to DVT
Immobility/bed rest
Post-operative
Pregnancy + post-partum
Oral contraceptives
Severe burns
Cardiac failure
Disseminated cancer
Superficial thrombophlebitis
Obesity
Old age
Previous/family history of DVT
What is Superficial thrombophlebitis?
Inflammation in superficial vein of leg
What can you do to prevent thromboembolism caused by bed rest?
Identify patients at high risk
Mobilise early + decrease bed rest
+/- aspirin
Low molecular weight heparin subcutaneously
Leg compression during surgery e.g. TED stockings + ‘flowtron boots’
Different types of pulmonary thromboembolisms + their effects
- massive coiled embolus in main PA - death
- small embolus lodges in peripheral PA - pulmonary infarct
- multiple repeated small emboli - pulmonary hypertension
What can be used to identify DVT in leg?
Ultrasound
What can be used to identify an embolism?
CT pulmonary angiogram
Why are NOAC/DOACs better than oral warfarin
Easier to manage - no tests needed
Warfarin requires many tests
Easy to accidentally overdose on warfarin
What does NOAC/DOAC stand for?
Noval/Direct Oral AntiCoagulant
Examples of NOAC/DOACs
Rivaroxaban
Apixaban
Dabigatron
Treatments of thrombosis
Clot busters/thrombolysis
Low molecular weight heparin
Oral warfarin
NOAC/DOAC
Embolectomy
Filters in IVc
Aspirin
Examples of clot busters
Streptokinase
Ateplase
How has warfarin work?
Inhibits synthesis of vitamin K dependent clotting factors
What drug increases PT and is monitored by regular INR measurements?
Warfarin
Conditions for which warfarin is used
DVT
Pulmonary embolism
Cardiac arrhythmias
After cardiac valve replacement
What tests are needed if you are in warfarin?
PT/INR test
What effect would a paracetamol overdose have on clotting tests?
Why?
PT raised
Paracetamol toxicity > liver failure
Prothrombin isn’t produced by the liver
What is prothrombin a test on?
Extrinsic pathway
Clotting factors made by the liver
What effect would a paracetamol overdose have on blood tests?
Raised PT
Raised ALT
What effect would a paracetamol overdose have on ALT tests?
Why?
Increased ALT
Hepatocytes die due to paracetamol toxicity
ALT leaks out of the damaged cell membranes
What is a paracetamol overdose treated with?
N-acetylcysteine
Why are pregnant women predisposed to DVT?
- Pregnancy blood is hypercoagulable
- The baby can compress venous outflow from legs and cause venous stasis
Why is low molecular weight heparin favoured over warfarin?
LMW heparins effective immediately
Warfarin takes a few days to become effective
What type of inhibitor is aspirin?
Non-competitive
What does aspirin do?
- Irreversible inhibits cylcooxygenase (enzyme for prostaglandin synthesis)
- platelets can’t produce thromboxane A2
- reduced platelet aggregation
What inhibits cyclooxgenase?
Aspirin - non competitively
Ibuprofen - competitively
What does low molecular weight heparin do?
Irreversible complexes with and activates antithrombin III
Bleeding time in aspirin
Prolonged
What does cyclooxgenase cataylse?
Prostaglandin synthesis
Where do the of thrombi that cause majority of pulmonary emboli arise from?
Deep veins of thigh + popliteal vein
What is most likely cause of thrombi occurring in veins
Blood stasis
What type of thrombi usually occur at site of endothelial injury?
Atrial and cardiac thrombi