Pathophysiology of ischaemia and infarction Flashcards
What are the 4 different kinds of hypoxia?
Hypoxic - low O2 or low PaO2
Anaemic - abnormal blood
Stagnant - abnormal delivery (occlusion/shock)
Cytotoxic - anaerobic metabolism
What factors affect O2 supply?
Inspired air Pulmonary function Blood constituents Blood flow Integrity of vasculature Tissue mechanics
What factors affect O2 demand?
Tissue requirements at baseline
Activity of tissue above baseline
How can IHD be caused by O2 supply issues?
Coronary artery atheroma Cardiac failure Pulmonary function Anaemia Previous MI causing damage
How can IHD be caused by demand issues?
High intrinsic demand of heart
Exertion and stress increases this
What are some clinical consequences of IHD?
MI TIA (symptoms of stroke that improve) Cerebral infarction Abdominal aortic aneurysm Peripheral vascular disease Cardiac failure
What is Poiseuilles law?
Flow depends on resistance and diameter of the vessel
What are the clinical effects of ischaemia?
Dysfunction
Pain
Physical damage to specialised cells
Cells with low met rates are safer (fat bone)
Define infarction
Ischaemic necrosis within a tissue produced by occlusion of either the arterial supply or venous drainage
What can cause infarction?
Thrombosis
Embolism
Strangulation
Trauma - ruptured/cut vessel
All stop blood flow
What does the degree of infarction depend on?
Time period
Tissue/organ
Pattern of blood supply
Previous disease
How long before there is irreversible damage following infarction?
20-30mins
Where are pale infarcts seen?
Solid tissues e.g. myocardium, spleen, kidney
24-28hr after
Where are red infarcts seen?
Loose tissues e.g. lung, liver
24-48hr after
What is reperfusion injury?
tissue damage caused by blood supply returning to tissue after period of ischaemia, which results in inflammation and oxidative damage rather than restoration of normal function
Describe the reparative processes seen in the heart following MI
Cell death Inflammation Macrophage phagocytosis of dead cells Granulation tissue Collagen deposition and scar formation
Whats a transmural infarction?
Necrosis affects full thickness of myocardium
What is a subendocardial infarction?
mostly limited to a zone of myocardium under the endocardial lining of the heart
What are some complications of MI
Arrhythmias Sudden cardiac death Angina Cardiac failure Cardiac rupture Reinfarction Pulmonary embolism secondary to DVT Papillary muscle dysfunction Mural thrombosis Ventricular aneurysm Dresslers syndrome
What is Dresslers syndrome?
Dressler’s syndrome is a type of pericarditis — inflammation of the sac surrounding the heart (pericardium). Dressler’s syndrome is believed to be an immune system response after damage to heart tissue or to the pericardium, from events such as a heart attack, surgery or traumatic injury
