8. Thrombosis And Embolism Flashcards
What is the definition of thrombosis?
Formation of a solid mass of blood within the circulatory system
Give 3 causes of thrombosis and an example of each
Abnormalities of vessel wall - eg atheroma.
Abnormalities of blood flow - eg turbulence.
Abnormalities of blood components - eg post-op decreased fibrinolytic activity and not moving around much.
How do arterial thrombi appear?
Pale, granular, lines of Zahn, lower cell content.
How do venous thrombi appear?
Soft, gelatinous, deep red, higher cell content.
What are the 5 possible outcomes of thrombosis? What are each?
Lysis - complete dissolution of thrombus due to fibrinolytic system being active.
Propagation - progressive spread of thrombosis.
Organisation - reparative process.
Recanalisation - channels form through thrombus.
Embolism - part breaks off, travels through blood stream, lodges as distant site.
What outcome of thrombosis is most likely when thrombi are small?
Lysis
In what direction does propagation of thrombosis occur in arteries and veins? Why?
Arteries - distally.
Veins - proximally.
As blood is stagnant behind thrombus in direction of blood flow.
What happens in organisation as an outcome of thrombosis?
Ingrowth of firboblasts and capillaries (undergoes fibrous repair), lumen remains obstructed.
Name 2 arterial effects of thrombosis, and what they depend on
Ischaemia and infarction - MI.
Depends on site and collateral circulation.
Name 4 consequences of venous thrombosis.
Congestion and oedema - pain and skin ulceration.
Ischaemia.
Infarction.
Embolism of part of thrombus - occlusion of artery eg PE.
What is the definition of embolism?
Blockage of a blood vessel by solid, liquid or gas at a site distant from its origin.
What is the most common type of embolism? Name 3 other types.
Thrombo-emboli (broken off of the thrombus).
Other are air, amniotic fluid, nitrogen, medical equipment, tumour cells.
Where do most pulmonary emboli arise from?
Deep veins of thigh and popliteal vein
What can cause pulmonary hypertension?
Multiple small pulmonary emboli
What does a large pulmonary emboli cause?
Sudden death, right-sided heart failure, cardiovascular collapse.
What are saddle emboli?
Large emboli that become lodges at the bifurcation of an artery, blocking booth branches. Occur at bifurcation of pulmonary arteries and result in sudden death.
Where do thromboemboli in systemic arteries arise from?
Left heart, aneurysms, thrombi on ulcerated atherosclerosis
Where do thromboemboli in systemic arteries embolise?
Lower extremities, brain, intestines, kidneys, spleen, arms.
Why are thrombi commonly seen in the left heart?
Infarcts commonly affect left ventricle, thrombi form on affected necrotic endothelium in ventricular cavity.
AF results in decreased atrial contraction, dilation of left atrium, stagnation of blood, thrombus forms.
Vegetations are commoner on valves in the left heart.
What are paradoxical emboli?
Thromboemboli that form in the systemic veins but embolise to the systemic arteries. Is rare.
In what two ways can paradoxical emboli manage to bypass the lungs?
Small emboli pass through arterioles-venous anastomoses in the pulmonary circulation. (Way fat droplets pass through lungs in fat embolism).
Larger emboli enter systemic circulation by passing through defects in interventricular septum or patent foramen ovale during coughing, lifting or straining.
Where do emboli from atheroma usually affect and so what do patients present with?
Intestine, presenting with abdominal pain.
What are transient ischaemic attacks?
Episodes of neurological dysfunction that appear suddenly, last minutes to hours, then disappear.
What are transient ischaemic attacks a result of?
Microscopic emboli, usually atheroemboli from the carotid arteries (or sometimes thromboemboli from the left heart), to the brain.
