Flashcards in Pathophysiology of Ischaemia and Infarction Deck (50)
What is hypoxia?
Relative lack of blood supply to the tissue/organ, leading to inadequate oxygen supply to meet the needs of that tissue/organ
What are the main types of hypoxia?
What is seen in hypoxic hypoxia?
Low inspired O2 level
Normal inspired O2 but low PaO2
What is seen in anaemic hypoxia?
Normal inspired O2 but abnormal blood
What is seen in stagnant hypoxia?
Normal inspired O2 but abnormal delivery, either local e.g. occlusion of a vessel or systemic e.g. shock
What is seen in cytotoxic hypoxia?
Normal inspired O2 but abnormal at tissue level
What factors affect oxygen supply?
Integrity of vasculature
What factors affect oxygen demand?
The tissue itself - different tissues have different requirements
Activity of the tissue above baseline value e.g. in exercise
What is ischaemia?
Inadequate blood supply to an organ or tissue
What is infarction?
Obstruction of the blood supply to an organ or tissue resulting in local cell death
Ischaemic necrosis within a tissue or organ in the living body
What is atheroma?
A localised accumulation of lipid and fibrous tissue in the intima of arteries
What does established atheroma in coronary arteries result in?
What does complicated atheroma in coronary arteries result in?
What do ulcerated or fissured atheromatous plaques result in?
Thrombosis, causing ischaemia or infarction
What can atheroma in the aorta result in?
What are the clinical consequences of atheroma?
Abdominal aortic aneurysm
Peripheral vascular disease
What is the effect of atheroma on blood flow, according to Poiseuille's formula?
Atheroma leads to narrowing of the vessel lumen due to occlusion or thrombus
A reduction in vessel radius in an atheromatous vessel results in a 16 fold reduction in blood flow
This reduced blood and therefore oxygen flow leads to ischaemia or infarction
What are the functional consequences of ischaemia?
Blood/O2 supply fails to meet demand due to low supply, high demand or both
What are the general consequences of ischaemia?
Acute - obvious signs and symptoms
Chronic - may go unnoticed over a long period of time, insidious onset
Acute on chronic - acute signs/symptoms on already compromised tissues
What are the biochemical consequences of ischaemia?
Normal aerobic metabolism affected
Anaerobic metabolism occurs, causing cell death
What are the cellular consequences of ischaemia?
Different tissues have variable O2 requirements so are variably susceptible to ischaemia
Cells with high metabolic rate e.g. cardiac cells and neurons are greatly and quickly affected by ischaemia
Cells with low metabolic rate e.g. fat cells are much less affected by ischaemia
What are the clinical consequences of ischaemia?
Physical damage of specialised cells
What are the potential outcomes of ischaemia?
No clinical effect
What might result in supply issues in IHD?
Coronary artery atheroma
Pulmonary function due to another disease causing pulmonary oedema e.g. left ventricular failure
What results in demand issues?
Increased exertion and stress
What causes infarction?
Occlusion of the arterial supply or the venous drainage
What might cause the cessation of blood flow?
What does the scale of damage resulting from ischaemia or infarction depend on?
Pattern of blood supply
What is the basic process of infarction?
Liberation of enzymes
Breakdown of tissue
Coagulative necrosis e.g. heart, lung
Colliquitive necrosis e.g. brain