Embolism

Question 1

What is the definition of an embolus?

Answer 1

A detached solid, liquid or gaseous mass within the circulation that is transported to a site distant to its origin

Question 2

What are the 3 main types of emboli?

Answer 2

Solid, liquid and gas

Question 3

List the types of solid emboli

Answer 3

thrombo-emboli (a blood clot that breaks free in the blood stream)
athero-emboli (atherosclerotic plaque that breaks off)
tumour emboli (metastasis)
bone marrow emboli (broken long bone fracture → marrow into the vessels forming an embolism)
foreign body emboli (e.g. infection - fungi from a dirty needle enters the circulation and forms a colony, breaks loose)

Question 4

List the types of liquid emboli

Answer 4

fat emboli (escape from bone marrow or injury to subcutaneous tissues)
amniotic fluid emboli

Question 5

List the types of gas emboli

Answer 5

air emboli (from injury to the lung or accidentally injected into blood stream)
nitrogen emboli (perfused from tissues)

Question 6

What are the sources of emboli in the systemic circulation?

Answer 6

thrombo-emboli

athero-emboli

Question 7

Where do embolisms originating in the systemic circulation usually end up?

Answer 7

Small vessels in the lower limbs (because in arterial circulation blood vessels get smaller further away from the heart)

Question 8

Where do embolisms originating from the venous circulation usually end up?

Answer 8

Usually travel through the R heart and end up in the lungs (pulmonary embolism). If they are in the portal venous system they will end up in the liver.

Question 9

What are the effects of a pulmonary embolus?

Answer 9

• Stops blood from R heart going into the lung
• Increased pressure in R ventricle (can’t unload the blood to the lungs)
• Ventilation-perfusion mismatch (not enough perfusion, less oxygen transfer to blood)
• Extent of the effects depend on the anatomical location of the embolism:

1. Main pulmonary artery at bifurcation: can cause acute right heart failure and sudden death
2. Large branch: can cause pulmonary haemorrhage and infarct
3. Smaller branch: can have no effect, or can cause pulmonary haemorrhage and infarct
4. Multiple smaller branches: causes chronic pulmonary hypertension and R heart failure

Question 10

Name the sites where solid emboli are involved.

Answer 10

Systemic “arterial” circulation
Venous system (which is associated with the pulmonary arterial system and portal system)
Lymphatic system

Question 11

What happens to an embolus?

Answer 11

Can either:

• dissolve
• develop superimposed thrombosis (thrombus develops on top of the embolus)
• becomes organised and re-canalised (incorporated into vessel wall causing narrowing of the lumen)

Question 12

Where do tumour, bone marrow and foreign body emboli usually occur?

Answer 12

Venous system

Question 13

Where will a solid embolism in the lymphatic circulation end up?

Answer 13

Lymph nodes

Question 14

What are the effects of fat embolism?

Answer 14

• Mechanical obstruction
• Fat is toxic to endothelium so it will set off inflammatory reaction (can also set off coagulation cascade)
• Fat embolism syndrome (pulmonary insufficiency, neuro symptoms, petechial rash, thrombocytopenia)

Question 15

How do amniotic fluid emboli occur? What are the effects?

Answer 15

• During childbirth the uterine veins may rupture
• Contents from amniotic sack enter the veins
• Biochemical effects and mechanical blockage
• Same as fat embolism syndrome (resp, neuro and petechial rash symptoms)

Question 16

What are the effects of an air embolism?

Answer 16

• Circulates and ends up in the R heart

- Acts as a physical obstruction and interferes with filling and output of the R heart