Pathophysiology of Ischaemia and Infarction Flashcards
What is the definition of ischaemia?
- Supply of oxygen to a tissue/organ is not enough for the demand of the tissue/organ
What are the 4 types of hypoxia?
- Hypoxic
- Anaemic
- Stagnant
- Cytotoxic
What causes hypoxic hypoxia?
- Low inspired O2 level
- Normal inspired O2 but low PaO2
What causes anaemic hypoxia?
- Normal O2 inspiration but blood abnormal
What causes stagnant hypoxia?
Normal inspired O2 but abnormal delivery
- Occlusion of vessels
- Systemic (e.g. shock)
What causes cytotoxic hypoxia?
- Normal inspired O2 but abnormalities at the tissue level
What factors affect oxygen supply?
- Inspired O2
- Pulmonary function
- Blood constituents
- Blood flow
- Integrity of vasculature
- Tissue mechanisms
What factors affect tissue demand?
- Type of tissue
- Activity of tissue above baseline
In ischaemic heart disease what are the supply issues?
- Coronary artery atheroma
- Cardiac failure
- Pulmonary function
- Pulmonary oedema (LVF)
- Anaemia
- Previous MI
What demand issues relate to ischaemic HD?
- Heart has a high demand
- Increases on exercise and stress
What type of atheroma will cause stable angina?
- Established
What type of atheroma will cause unstable angina?
- Complicated
What are the functional effects of ischaemia?
- Blood/O2 supply doesn’t meat demand so demand increases further leading to angina
What is released due to this lack of O2/blood supply?
- Lactic acid from anaerobic respiration
- Ultimately, if not converted back into pyruvate leads to cell death
What are the clinical effects of ischaemia?
- Dysfunction
- Pain
- Physical damage to specialised cells that can’t be replaced