Pathophysiology of isachemia and infraction

Question 1

What is isachaemia?

Answer 1

• lack if blood supply to a tissue/organ due to little O2 supply
• hypoxia

Question 2

Types of hypoxia

Answer 2

Hypoxic

• low inspired O2 level
• normal inspired O2 level but low PaO2

Anaemic
-normal inspired O2 but blood abnormal

Stagnant

• normal inspired O2 but abnormal delivery
  a) local ( occlusion of vessel)
  b) systemic ( shock)

Cytotoxic
-normal inspired O2 but abnormal at tissue level

Question 3

State the factors that affect O2 supply

Answer 3

1. Inspired O2
2. Pulmonary function
3. blood constituents
4. Blood flow
5. Integrity of vasculature
6. Tissue mechanisms

Question 4

State the factors that affect O2 demand

Answer 4

• tissue itself

- activity of tissue

Question 5

Atheroma stages and its causes

Answer 5

Establish atheroma in CA > Stable angina

Complicated atheroma in CA > unstable angina

Ulcerated/fissuered plaques > thrombosis > isachaemia/infarction

Atheroma in aorta > aneurysm

Question 6

What can isachaemia lead to? !!!!!!!!!!!!!!!!

Answer 6

• MI
• TIA
• cerebal infarction
• abdominal aortic aneurysm
• peripheral vascular disease
• cardiac failure
• coronary artery disease > MI > cardiac failure

Question 7

Effect of isachaemia ( functional/general)

Answer 7

Functional

• blood/O2 supply fails to meet demand due to decreased supply. This increases the demand
• related to rate of onset

General

• acute
• chronic
• acute-on-chronic

Biochemical

• normal aerobic metabolism
• anaerobic metabolism

Cellular

• different tissues have variable O2 requirement + susceptible to ischaemia
• cells with high/low metabolic rate

Question 8

Clinical effects of isachaemia

Answer 8

• dysfunction
• pain
• physical damage( specialised cells)

Question 9

What is an infarction?

Answer 9

• necrosis of tissue/organ due to isachaemia

- due to occlusion of arterial supply/venous drainage

Question 10

Causes of infarction

Answer 10

1. thrombosis
2. embolism
3. strangulation ( gut)
4. trauma (cut/ruptured vessel)

Question 11

Severity of infarction is dependent on what factors?

Answer 11

• time
• tissue/organ
• pattern of BA
• previous disease

Question 12

Pathophysiology of infarction

Answer 12

Anaerobic metabolism > cell death > liberation of enzymes > breakdown of tissue

• coagulative necrosis ( heart, lung)
• colliquitive necrosis ( brain)

Question 13

Pathophysiology of myocardial infarction

Answer 13

-coronary arterial obstruction leads to decreased BF to region of myocardium > isachaemia, rapid myocardial dysfunction > myocyte death

Question 14

Pathophysiology of myocardial infaction ( time)

Answer 14

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Question 15

Appearances of infarcts

Answer 15

• few hours-12 hours swollen mitochondria on electron microscopy
• 24-48hrs microscopically accute inflammation at edge of infarct ; loss of specialised cell features
• End result :scar replaces area of tissue damage
• reperfusion injury

Question 16

Myocardial infarction pathophysiology (time)

Answer 16

njb

Question 17

Types of MI

Answer 17

Transmural infarction
-ischaemic necrosis affects full thickness of myocardium

Subendocardial infarction
-ischaemic necrosis limited to a region of myocardium under the endocardial lining of heart

Question 18

Transmural Infarction vs Subendocardial Infarction

Answer 18

-histological features same + repair time ( granulation tissue>fibrosis in subendocardial infarct shorter vs transmural infarct)

Question 19

Complications of MI

Answer 19

• death
• arrythmias, angina, CF, cardiac rupture
• pericarditis, pulmonary embolism secondary to DVT
• reinfarction, papillary muscle dysfuncion; necrosis/rupture> mitral incompetence
• mural thrombosis, ventricular aneurysm, dresslers syndrome