Pathophysiology of ischaemia and infraction (part 1) Flashcards
Define ischaemia?
relative lack of blood supply to tissue/organ leading to inadequate O2 supply to meet needs of tissue/organ: hypoxia
What is hypoxic?
a) low inspired O2 level
b) normal inspired O2 but low PaO2
What is anaemic?
normal inspired O2 but blood abnormal
not enough haemoglobin to carry oxygen
What are the 4 types of hypoxia?
hypoxic
anaemic
stagnant
cytotoxic
What is stagnant hypoxia?
normal inspired O2 but abnormal delivery
What are 2 types of stagnant hypoxia?
local e.g. occlusion of vessel
systemic e.g. shock
What is cytotoxic hypoxia?
normal inspired O2 but abnormal at tissue level
tissue cannot use oxygen that is being delivered to it
What factors effect oxygen supply?
inspired O2
pulmonary function
blood constituents
blood flow
integrity of vasculature
tissue mechanisms
What are 2 factors affecting oxygen demand?
- tissue itself - different tissues have different requirements
- activity of tissue above baseline value
What are examples of supply issues in ischaemic HD?
coronary artery atheroma
cardiac failure (flow)
pulmonary function - other disease or pulmonary oedema (LVF)
Anaemia
previous MI
What does it mean that the heart has a high intrinsic demand?
the control of the hearts output/ contraction force
increase cardiac output
What is atheroma/ atherosclerosis?
localized accumulation of lipid and fibrous tissue in intima of arteries
What is the clinical correlation of established atheroma in a cornionary artery?
stable angina
What is the clinical correlation of complicated atheroma in coronary artery?
unstable angina
What is angina?
when the coronary arteries receive not a sufficient blood supply
What are the clinical manifestations of stable angina?
pain on exertion but not at rest
When does a complicated atheroma in coronary artery occur?
something has happened to the atheroma, hemorrhage or plaque rupture
What happens if the plaque ulcerates of fissures?
thrombosis –> ischemia/infarction
What is the clinical consideration of atheroma in the aorta?
aneurysm
What is infarction?
lecture definition:
ischemic necrosis within a tissue/organ in living body produced by occlusion of either the arterial supply or venous drainage
death of tissue as a result of failure of blood supply
commonly due to obstruction of blood vessel by a atheroma or narrow of vessel channel
List 6 clinical consequences of atheroma/ischemia?
MI
TIA (transient ischemic attack)
cerebral infarction
abdominal aortic aneurysm
peripheral vascular disease
cardiac failure
Put these terms in order of events
- MI
- coronary artery disease
- cardiac failure
coronary artery disease
MI
cardiac failure
What can a change in the vessel wall cause? (Virchow’s triad)
thrombosis
Name the components of Virchow’s triad?
What are 3 categories of the effects of ischaemia?
acute
chronic
acute-on-chronic
What are the biochemical effects of ishaemia?
decrease oxygen –> anaerobic metabolism –> cell death
Are all cells equally susceptible to ischemia?
no, different tissues have variable o2 requirement and are variably susceptible to ischemia
What tissues are more affected ischaemia?
cells with high metabolic rate
Name cells with a high metabolic rate
specialized cells…
neurons
heart muscles cells
nerve cells
What are the clinical effects of ischaemia?
dysfunction
pain
physical damage - specialized cells
In the heart what can little bits of ischemia cause?
arrhythmia
What would you call myocardial pain?
angina
What are the outcomes of ischaemia?
no clinal effect
resolution versus therapeutic intervention
infarction
What is the aetiology of infarction?
cessation of blood flow
Name 4 things that can cause infarction? (cessation of blood flow)
thrombosis
embolism
strangulation e.g. gut
trauma - cut/ ruptured vessel
What are 4 factors which dictate the scale of damage of ischemia?
time period
tissue organ
pattern of blood supply
previous disease
How does anaerobic metabolism cause necrosis?
causes cell death –> liberation of enzymes –> breakdown of tissues (necrosis)
Where would you get coagulation necrosis?
lung
heart
Where would you get colliquitive necrosis?
brain
How long does it take to get myocyte necrosis?
20-40 minutes
