Embolism, Infarction & Shock

Question 1

Embolism

Answer 1

An embolus is a mass of material in the vascular system that is able to become lodged in a blood vessel and block circulation

The majority of emboli are thrombi

Question 2

Sources of emboli

Answer 2

• Pieces of thrombus
• Infected lesions
• Gas bubbles
• Fat and bone marrow
• Amniotic fluid

Question 3

Pulmonary embolism

Answer 3

Pulmonary emboli usually occur as a complication of DVT

60-80% are clinically silent

Pulmonary emboli of key vessels can lead to sudden death, right heart failure and cardiovascular collapse

Pulmonary emboli of mid-sized vessels can lead to pulmonary haemorrhage

Question 4

Arterial emboli

Answer 4

Arterial emboli are commonly from intracardiac mural thrombi

They can block a variety of sites, causing tissue infarction in the surrounding area

Question 5

Infarction

Answer 5

An infarct is an area of ischaemic necrosis caused by occlusion of the arterial supply or venous drainage

99% of infarctions are a result of emboli

Question 6

Cause of infarction

Answer 6

• Emboli
• Vasospasm
• Haemorrhage of atherosclerotic plaques
• Vessel compression
• Traumatic rupture

Question 7

Morphology of infarcts

Answer 7

The shape of an infarction indicates its position

• Wedge-shaped = lung
• Triangular = kidney
• Scarred = spleen

Question 8

White infarction

Answer 8

A white infarction lacks haemorrhage and occurs in solid organs with end arterial circulation

Question 9

Red infarction

Answer 9

A red infarction is haemorrhagic

Question 10

Septic infarction

Answer 10

An infected infarct

Question 11

Bland infarction

Answer 11

An infarct that is not infected

Question 12

Outcomes of infarction

Answer 12

The outcome of an infarction depends on several factors

• Nature of the blood supply
• Rate of development
• Vulnerability of tissue
• Oxygen content of the blood

Question 13

Myocardial infarction

Answer 13

A myocardial infarction has several stages, it is not visible until at least 6 hours have passed

• 24 hours = colour change and inflammation seen
• Days/weeks = macrophage infiltration and fibrosis
• Months = fibrous scar

Question 14

Shock

Answer 14

Shock is the end pathway for many clinical events

It is due to inadequate tissue perfusion and is characterised by systemic hypotension

Question 15

Causes of shock

Answer 15

• Low cardiac output (e.g. heart failure)
• Hypovolaemic shock (e.g. blood loss)
• Septic shock (e.g. pooling of blood at peripheries)

Question 16

Symptoms of shock

Answer 16

Pale/bluish skin
Excessive thirst 
Weak pulse 
Nausea 
Rapid breathing 
Altered concious state 
Restlessness 
Irritability