Ischaemia and infarction

Question 1

ischaemia

Answer 1

relative lack of blood supply to tissue/ organ leading to inadequate oxygen supply to meet needs of tissue/ organ: hypoxia

Question 2

types of hypoxia

Answer 2

hypoxic, anaemic,

Question 3

hypoxic hypoxia

Answer 3

low inspired oxygen or normal inspired oxygen but low partial pressure of oxygen

Question 4

anaemic hypoxia

Answer 4

normal inspired oxygen but blood abnormal

Question 5

stagnant hypoxia

Answer 5

normal inspired oxygen but abnormal oxygen delivery eg occlusion of vessel (local) and shock (systemic)

Question 6

cytotoxic hypoxia

Answer 6

normal inspired oxygen but abnormal at tissue level

Question 7

factors affecting oxygen supply

Answer 7

inspired oxygen, pulmonary function, blood constituents, blood flow, integrity of vasculature, tissue mechanisms

Question 8

factors affecting oxygen demand

Answer 8

tissue type, activity of tissue above baseline value

Question 9

ischaemic heart disease

Answer 9

supply issues- coronary artery atheroma, cardiac failure, pulmonary function- other disease or pulmonary oedema, anaemia, previous MI
demand issues- heart has high intrinsic demand, exertion/ stress

Question 10

clinical correlation between ischaemic heart disease and atheroma

Answer 10

ulcerated/ fissured plaques leads to thrombosis which leads to ischaemia and or infarction

Question 11

functional effects of ischaemia

Answer 11

blood oxygen supply fails to meet demand due to decreased supply and increased demand or both. related to rate of onset. can be general, chronic, acute on chronic

Question 12

cellular effects of ischaemia

Answer 12

different tissues have variable oxygen requirement and variably susceptible to ischaemia, neurons, heart cells, renal tubular cells affected more than fat, bone etc

Question 13

clinical effects of ischaemia

Answer 13

dysfunction, pain, physical damage

Question 14

outcome of ischaemia

Answer 14

no clinical effect, resolution, infarction

Question 15

aetiology of infarction

Answer 15

thrombosis, embolism, strangulation eg gut, trauma

Question 16

scale of damage of ischamia and infarction depends on

Answer 16

time period, tissue organ, pattern of blood supply, previous disease

Question 17

types of necrosis

Answer 17

coagulative and colliquitive

Question 18

myocardial ischaemia process and time

Answer 18

anaerobic metabolism and onset of ATP depletion, loss of myocardial contractility, ultrastructural changes eg myofibrillar relaxation, glycogen depletion, cell and mitochondrial swelling. all happens within a few mins. 20-30mins means irreversible damage. 20-40 mins myocyte necrosis. 1 hour to injury to microvasculature

Question 19

appearances of infarcts over time

Answer 19

less than 24 hours swollen mitochondria, 24-48 hours acute inflammation initially at edge of infarct, loss of specialised cell features, 72 hours- chronic inflammation, macrophages remove debris, granulation tissue, fibrosis

Question 20

pale infarcts occur in

Answer 20

myocardium, spleen, kidney, solid tissues. turn yellow and red periphery after 72 hours

Question 21

red infarcts occur in

Answer 21

lung, liver loose tissues, previously congested tissue, venous occlusion, secondary/ continuing blood supply. little change after 72 hours

Question 22

end result of infarct

Answer 22

scar replaces area of tissue damage (more white) and shape depends on territory of occluded vessel

Question 23

reparative processes of myocardial infarction

Answer 23

cell death, acute inflammation, macrophage phagocytosis of dead cells, granulation tissue, collagen deposition, scar formation

Question 24

transmural infarction

Answer 24

ischaemic necrosis affects full thickness of the myocardium

Question 25

acute infarcts are classified according to

Answer 25

whether there is elevation of the ST segments on the ECG.

Question 26

non stemi

Answer 26

no ST segment elevation but a significantly serum troponin level. thought to correlate with a subendocardial infarct

Question 27

effects infarction

Answer 27

site of dependent, size of infarct, death, dysfunction, contribution of previous disease/ infarction

Question 28

complications of myocardial infarction

Answer 28

sudden death, arrhythmias, angina, cardiac failure, cardiac rupture, papillary muscle, reinfarction, pericarditis, papillary muscle dysfunction, pulmonary embolism secondary to deep vein thrombosis, mural thrombosis, ventricular aneurysm, dresslers syndrome