8. Thrombosis And Embolism

Question 1

What is the definition of thrombosis?

Answer 1

Formation of a solid mass of blood within the circulatory system

Question 2

Give 3 causes of thrombosis and an example of each

Answer 2

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.

Question 3

How do arterial thrombi appear?

Answer 3

Pale, granular, lines of Zahn, lower cell content.

Question 4

How do venous thrombi appear?

Answer 4

Soft, gelatinous, deep red, higher cell content.

Question 5

What are the 5 possible outcomes of thrombosis? What are each?

Answer 5

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.

Question 6

What outcome of thrombosis is most likely when thrombi are small?

Answer 6

Lysis

Question 7

In what direction does propagation of thrombosis occur in arteries and veins? Why?

Answer 7

Arteries - distally.
Veins - proximally.
As blood is stagnant behind thrombus in direction of blood flow.

Question 8

What happens in organisation as an outcome of thrombosis?

Answer 8

Ingrowth of firboblasts and capillaries (undergoes fibrous repair), lumen remains obstructed.

Question 9

Name 2 arterial effects of thrombosis, and what they depend on

Answer 9

Ischaemia and infarction - MI.

Depends on site and collateral circulation.

Question 10

Name 4 consequences of venous thrombosis.

Answer 10

Congestion and oedema - pain and skin ulceration.
Ischaemia.
Infarction.
Embolism of part of thrombus - occlusion of artery eg PE.

Question 11

What is the definition of embolism?

Answer 11

Blockage of a blood vessel by solid, liquid or gas at a site distant from its origin.

Question 12

What is the most common type of embolism? Name 3 other types.

Answer 12

Thrombo-emboli (broken off of the thrombus).

Other are air, amniotic fluid, nitrogen, medical equipment, tumour cells.

Question 13

Where do most pulmonary emboli arise from?

Answer 13

Deep veins of thigh and popliteal vein

Question 14

What can cause pulmonary hypertension?

Answer 14

Multiple small pulmonary emboli

Question 15

What does a large pulmonary emboli cause?

Answer 15

Sudden death, right-sided heart failure, cardiovascular collapse.

Question 16

What are saddle emboli?

Answer 16

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.

Question 17

Where do thromboemboli in systemic arteries arise from?

Answer 17

Left heart, aneurysms, thrombi on ulcerated atherosclerosis

Question 18

Where do thromboemboli in systemic arteries embolise?

Answer 18

Lower extremities, brain, intestines, kidneys, spleen, arms.

Question 19

Why are thrombi commonly seen in the left heart?

Answer 19

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.

Question 20

What are paradoxical emboli?

Answer 20

Thromboemboli that form in the systemic veins but embolise to the systemic arteries. Is rare.

Question 21

In what two ways can paradoxical emboli manage to bypass the lungs?

Answer 21

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.

Question 22

Where do emboli from atheroma usually affect and so what do patients present with?

Answer 22

Intestine, presenting with abdominal pain.

Question 23

What are transient ischaemic attacks?

Answer 23

Episodes of neurological dysfunction that appear suddenly, last minutes to hours, then disappear.

Question 24

What are transient ischaemic attacks a result of?

Answer 24

Microscopic emboli, usually atheroemboli from the carotid arteries (or sometimes thromboemboli from the left heart), to the brain.

Question 25

Give 4 predisposing factors for DVT

Answer 25

Immobility
Post-op
Pregnancy and post-partum
Oral contraceptives
Severe burns
Cardiac failure
Disseminated cancer

Question 26

Name a way of prevention of thromboembolic disease

Answer 26

General prophylaxis eg anticoagulants, compression stockings, flowtron boots

Question 27

What drug is most commonly used as prophylaxis against thrombosis, and also to treat thrombosis?

Answer 27

Low molecular weight heparin

Question 28

What is aspirin used for?

Answer 28

Phrophylactic against DVT, patients with increased risk of MI and stroke

Question 29

What is warfarin used for?

Answer 29

Prophylaxis against thrombosis and to treat thrombosis.

Question 30

What does warfarin interfere with?

Answer 30

Vitamin K metabolism

Question 31

When is low molecular weight heparin used, and when is warfarin used?

Answer 31

Heparin works immediately, warfarin takes a few days

Question 32

How are fat emboli caused?

Answer 32

Bone fractured, done marrow dat cells injured break up, release oil droplets, coalesce over period of few days, sucked into venules torn by fracture, so symptoms seen a couple of days after fracture. Can pass into many organs.

Question 33

What happens in air embolism?

Answer 33

Negative pressure in veins of chest and head in inspiration means veins can draw in air after trauma. Air transported to right heart, bubbles gather as frothy mass that stops circulation.

Question 34

When can air embolism occur other than in trauma?

Answer 34

Labour

Question 35

How do amniotic fluid embolisms occur?

Answer 35

Amniotic fluid enters maternal circulation through tear in amniotic membranes.

Question 36

What does amniotic fluid embolism cause?

Answer 36

Sudden respiratory distress, hypotension, seizures, loss of consciousness, disseminated intravascular coagulation. Can also contain microscopic emboli of foetal origin, which are then found in the lungs.

Question 37

What are talcum emboli?

Answer 37

Microscopic foreign bodies with which drugs have been cut, found in lungs of IVDUs. Produce a marked foreign body reaction and pulmonary symptoms.