Pathophysiology of Ischaemia and Infarction Flashcards
What are the two reasons for ischaemic heart disease?
Supply issues
Demand issues
What kind of supply issues can cause ischaemic heart disease?
Coronary artery atheroma Cardiac failure Pulmonary function Pulmonary oedema Anaemia Previous MI
What kind of demand issues cause ischaemic heart disease?
Heart has a high intrinsic demand due to exertion or stress
What is the outcome of Ischaemia?
Can be no clinical effect
Resolution on its own or with therapeutic intervention
Infarction
What factors affect the scale of damage of infarction?
Time period
Tissue or organ
Pattern of blood supply
Previous disease
How long does severe iscahemia take to cause irreversible damage?
20-30 minutes
What is infarction?
Obstruction of the blood supply to an organ or region of tissue, typically by a thrombus or embolus, causing local death of the tissue
What is stagnant hypoxia?
Normal inspired O2 but abnormal delivery
What is cytotoxic hypoxia?
Normal inspired oxygen but abnormal at tissue level
What causes stagnant hypoxia?
Local effects such as occlusion of vessels
Systemic effects such as shock
What are the reparative processes that happen in order during myocardial infarctions?
- Cell death
- Acute inflammation
- Macrophage phagocytosis of dead cells
- Granulation tissue
- Collagen deposition (fibrosis)
- Scar formation
How long does it take for the formation of dense collagenous scars in an MI?
2 months or more
What are the effects of infarction?
Death
Dysfunction
What is a myocardial infarction?
Myocardial infarction is the partial death of heart tissue commonly known as heart attack.
What is ischaemia?
Relative lack of blood supply to a tissue or organ leading to inadequate oxygen supply to meet the needs of that tissue or organ
What are the factors affecting oxygen supply?
Inspired oxygen Pulmonary function Blood constituents Blood flow Integrity of vasculature Tissue mechanisms
What is atheroma or atherosclerosis?
Localised accumulation of lipid and fibrous tissue in the intima of arteries
What does atheroma in the aorta cause?
An aneurysm
What does an established atheroma in a coronary artery cause?
Stable angina
What does a complicated atheroma in a coronary artery cause?
Unstable angina
What does an ulcerated or fissured plaque cause?
Thrombosis which leads to ischaemia or infarction
What are the clinical consequences of an atheroma?
MI Transient ischaemic attack Cerebral infarction Abdominal aortic aneurysm Peripheral vascular disease Cardiac failure
What is the clinical effect of Ischaemia?
Dysfunction
Pain
Physical damage of cells
What are the possible outcomes of ischaemia?
No clinical effect
Resolution on its own or by therapeutic intervention
Infarction
