2.2 Pathology of MI

Question 1

what causes cell injury?

Answer 1

occurs when cells are stressed so severely that they are no longer able to adapt to oxygen deprivation, toxins, infectious agents and physical trauma

Question 2

What is ischaemia?

Answer 2

Loss of blood supply from impeded arterial flow or reduced venous drainage

Question 3

define infarction

Answer 3

occurs in any tissue in which there is sufficient ischaemia to cause tissue death or tissue necrosis

Question 4

What are the arterial causes of infarction?

Answer 4

complete blocage by thrombosis or emboism

Question 5

What are the types of necrosis?

Answer 5

Coagulative: denaturation of proteins, preservation is the cell outlines, classic finding in MI - get ghost cells
Liquefactive: Enzyme digesting dominant, classic finding in abscess and cerebral infarct
Caseous: found in TB (mainly at apex of lung)
Fat: focal areas of fat destruction, classic in pancreatitis

Question 6

risk factors for atherosclerosis

Answer 6

Male 
family history 
Hypertension 
Smoking 
diabetes mellitus 
Hypercholesterolaemia

Question 7

What is an unstable plaque?

Answer 7

Has a thin fibrous cap meaning that it can rupture easily and cause thrombosis. They also have new vessels which can rupture leading to haemorrhage

Question 8

What are the steps in coronary artery occlusion?

Answer 8

Acute plaque changes - disrupted plaque
Platelets undergo adhesion, aggregation and activation
Vasospasm
Activation of extrinsic pathway of coagulation, increase in thrombus size
within minutes complete occlusion of the artery

Question 9

features of transmural infarction

Answer 9

Full thickness ischaemia necrosis of the ventiricular wall
Distribution of a single coronary artery
ST elevation

Question 10

features of subendocardial infarction

Answer 10

Ischaemic necrosis limited to the inner 1/3 of ventricular wall
May involve the distribution of several coronary arteries
least well perfused area normally
non ST elevated

Question 11

Complications of MI (outside- inside)

Answer 11

Contractile dysfunction - arrhythmia - pericarditis - myocardial rupture - mural thrombosis - ventricular aneurysm

Question 12

what is haemopericardium

Answer 12

escape of blood from the ventricles into the pericardial cavity

Question 13

define ischaemic heart disease

Answer 13

syndromes arising due to myocardial ischaemia - angina, sudden death, myocardial infarction, chronic ischaemic heart disease with heart failure

Question 14

What is the pathogenesis of MI

Answer 14

coronary artery occlusion
Increased myocardial demand
Haemodynamic compromise
Presence or absence of collatereal vessels

Question 15

Macroscopic and microscopic changes of MI at day 1

Answer 15

Macro: subtle changes, dark mottling, subtle softening
Micro: scant neutrophils, coagulative necrosis, haemorrhage, contraction bands

Question 16

Macroscopic and microscopic changes of MI at 2 days

Answer 16

macro: mottled appearance with yellow/tan infarct
micro: coagulation necrosis and neutrophils

Question 17

Macroscopic and microscopic changes of MI at 1 week

Answer 17

macro: hyperaemic border and central tan softening
micro: disintegration of necrotic myofibres, dying neutrophils and macrophages

Question 18

Macroscopic and microscopic changes of MI at 2 weeks

Answer 18

macro: maximalls yellow with depressed infarct borders
micro: phagocytosis, granulation tissue and early fibrosis

Question 19

Macroscopic and microscopic changes of MI at 2 months

Answer 19

macro: white scarring
micro: dense collagenous scar

Question 20

Mnemonic for complications

Answer 20

Cardiac patients make me very angry

• contractile dysfunction and arrhythmia
• Pericarditis
• Myocardial rupture
• Mural thrombosis
• Ventricular aneurysm

Question 21

what are the complications of ventricular aneurysm

Answer 21

Mural thrombus, arrhythmia, LVF