Lecture 10 - Thrombosis And Embolus Flashcards
What is a thrombus?
Formation of a solid mass of blood WITHIN the circulatory system
What is a clot?
A mass of blood OUTSIDE the vessel wall
Are thrombus and clot interchangeable terms?
NO
THROMBUS = solid mass INSIDE vessel
CLOT = mass of blood OUTSIDE vessel
What is Virchow’s Triad?
The 3 main factors needed for a thrombus to occur
What are the 3 factors of Virchow’s triad that can cause thrombus formation?
Abnormal:
Vessel wall
Blood flow
Blood components
How can the endothelium of blood vessels be damaged?
Atheroma
Inflammation (vasculitis)
Direct injury
Damage to heart (MI, Aortic valve stenosis)
What does Transmural mean?
Spanning the full thickness of the wall
What can cause stasis (slowing) of the blood?
Narrowing of vessels
Immobility
Low blood pressure
What can cause narrowing of blood vessels leading to stasis?
Stenosis
Atherosclerosis
How does immobility lead to stasis?
Skeletal muscle contraction not contributing to squeezing blood to heart
What can cause turbulent blood flow in the heart? (Healthy flow is laminar flow)
Defects in wall and heart valves
Atrial fibrillation
Dead cardiac muscle
What is the technical term for the blood being sticky?
It is in a hypercoagulable state
Who are more at risk of stasis
Smokers
Pregant/postpartum
COVID-19 patients
Why are smokers at risk of hypercoagulable blood?
More factor XII
Why are pregnant women more at risk of hypercoagulable blood?
More fibrinogen
Why are COVID-19 patients more at risk of hypercoagulable blood?
More cytokines
What are the properties of a Arterial Thrombus?
Pale
Granular
Low cell content (mainly platelets and fibrin)
Lines of Zahn
What cause the Iines of Zahn in an Arterial thrombus?
Layering of platelets, fibrin and RBCs
Why are venous thrombi redder than arterial thrombi?
Higher cell content
They are also softer
What is the function of Tissue plasminogen activator?
Converts Plasminogen to plasmin
If somebody has issues with Thrombi, what type of drug can be given?
Recombinant Tissue plasminogen activator
Why does giving streptokinase/recombinant tissue plasminogen activator help deal with a thrombus?
Increases Fibrinolysis and breaks down tthe fibrin dissolving the thrombus
More plasminogen → plasmin
What is the lysis outcome of a thrombus?
When fibrinolysis breaks down the thrombus (must be small) and blood flow restablished
What is propagation outcome of Thrombosis?
Progressive spread of thrombosis through the body
If a Thrombus propagates anterograde what does this mean?
Spreads proximally in the veins
If a Thrombus propagates retrograde what does this mean?
Distally in arteries
What is the organisation outcome of a thrombus?
Repair starts
Fibroblasts and capilaries grow inwards in vessel
Lumen is still BLOCKED
What is the recanalisation outcome of Thrombosis?
When one or more holes forms through the thrombus normally partially restoring blood flow
What is an Embolism?
When part of a thrombus breaks off and gets logged at a different site
What is Deep Vein Thrombosis (DVT) and how does it often cause Pulmonary Embolisms (PE)?
When thrombus forms in lower limb
Part breaks off and travels through the Inferior Vena cava, RA, RV through pulmonary artery causing Pulmonary embolism since it blocks the first capillary network it contacts
What are normally the effects of thrombosis in the venous system?
Congestion
Oedema
Ischaemia
Infarction
What is the effect of Cavernous sinus thrombosis?
Neurological conditions
What can Uteroplacental thrombosis cause?
Miscarriage
Poor fetal development
What is more damaging Arterial thrombosis or venous thrombosis?
Arterial thrombosis
What is more damaging Arterial thrombosis or venous thrombosis?
Arterial thrombosis
What are the typical effects of arterial thrombosis on tissue?
Ischaemia
Infarction
What is the normal effect of a Cerebral Artery Thromobsis?
Common cause of Ischaemic stroke
What is the normal effect of a Coronary Artery Thromobsis?
Myocardial infarction (MI)
What is the normal effect of a Mesenteric Artery and/or Renal artery Thromobsis?
Kidney damage
What is the normal effect of a Femoral, Iliac or Popliteal Artery Thromobsis?
Ischaemia to affected area of limb
What indicates a thrombus in a blood vessel on a histological image?
Not clear space in the lumen of the blood vessel
How can you see areas that have been damaged by myocardial infarction/ ischaemic damage of heart?
Usually replaced with areas of white fibrous scar tissue (cant conduct electrical signals, lead to arrhythmias and heart failure)
What is a thrombo-embolus?
An embolism that is caused by a piece of thrombus breaking off an blocking a vessel
Why can endocardial thrombi (in heart) have so many different negative effects/sites of damage?
Fragments of thrombus travel through aorta to many parts of body:
-Cerebral arteries
-Renal artery
-Mesenteric artery
-iliac/femoral arteries
What thromboembolism can a thrombus forming in a carotid artery do?
Embolism into cerebral circulation causing ischaemic stroke
What can happen (thromboembolism) when a thrombus forms in the abdominal artery?
Acute limb ischaemia
(Iliac, femoral or popliteal artery occluded)
What are risk factors for developing a DVT?
Immobility
Post operation
Pregnancy
Oral contraceptives
sever burns
How does a leg affected by DVT usually appear?
Unilateral leg swelling
Redness
What are the 3 levels of complication of a pulmonary thromboembolism?
Sudden death
Pulmonary infarct
Pulmonary hypertension
What gets blocked when sudden death occurs from a Pulmonary thromboembolism?
Massive embolus in main pulmonary artery
(60% reduction in blood flow to lungs)
What gets blocked when pulmonary infarct occurs from a Pulmonary thromboembolism?
Small embolus in peripheral pulmonary artery
What gets blocked when pulmonary hypertension occurs from a Pulmonary thromboembolism?
Multiples small repeated emboli
May cough up blood but should be fine
What are the other types of embolism besides thromboembolism?
Air embolism
Amniotic fluid embolism
Nitrogen embolism (The bends)
Tumour cells (disseminated malignancy)
Fat/bone marrow (post trauma0
How can air cause an embolism?
Air bubble blocks blood vessels (pulmonary embolism possible)
How can an amniotic fluid embolism occur?
During labour or C-section amniotic membrane tears and amniotic fluid can cause embolism in lungs
What is cardiac Myxoma?
Tumour that starts in the heart
Where do cardiac myxomatosis usually develop and how can they cause embolisms?
Develop LA, then LV then out to body and can cause blockages of vessels
How can you prevent thrombosis and thromboembolism in hospital patients?
Identify high risk patients
Give heparin (activates Antithrombin)
Limit bed rest
Aspirin (prevents prodcution of thromboxane)
Leg compressions in surgery (mimic action of skeletal muscle squeezing blood back to heart)
What does Well’s score indicate?
Likeliness of having DVT
What can be given if you suspect a DVT?
Anticoagulant therapy
Ultra sound
Heparin
What is an Embolectomy?
Surgically remove the embolus
Commonly done for legs with acute limb ischaemia
What are common Thombolytic drug to treat thromboemboli or thrombus?
Why are these given?
Recombinant tissue plasminogen activators:
-Streptokinase
-Ateplase
Stimulate conversion of Plasminogen to Plasmin so more fibrolysis can be done to break down thrombi
What oral coagulants can be give to treat thrombi or thromboemboli?
(Anti factor 10)
Rivaroxaban
Apixaban
Dabigatran
What is the problem with oral warfarin?
Needs constant monitoring
