Ischaemic disease pathophysiology
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Ischaemic Disease Pathophysiology: Key Mechanisms and Processes
Macrovascular and Microvascular Pathophysiology in Ischaemic Heart Disease
Ischaemic heart disease (IHD) is primarily caused by reduced blood flow due to blockages or dysfunction in the coronary arteries. This can involve both large (macrovascular) vessels, such as those affected by atherosclerotic plaques, and small (microvascular) vessels, where endothelial dysfunction and impaired coronary flow reserve play a significant role. These macro- and microvascular abnormalities often coexist and interact, contributing to the complexity of IHD. For example, coronary vasospasm and microvascular dysfunction are linked to the development of vulnerable plaques and increased inflammation, highlighting the interplay between different vessel types in disease progression .
The Ischaemic Cascade and Myocardial Dysfunction
The pathophysiology of myocardial ischaemia follows a sequence known as the ischaemic cascade. Initially, there are biochemical disturbances, followed by diastolic and systolic dysfunction, and then electrocardiographic changes. Painful angina is a late event in this cascade, meaning significant cellular and functional changes occur before symptoms appear. Additionally, phenomena such as myocardial stunning (temporary loss of function after blood flow returns) and hibernating myocardium (chronic reduction in function due to persistent low blood flow) are important adaptive responses to ischaemia 218.
Ischaemia-Reperfusion Injury and Inflammatory Responses
When blood flow is restored to ischaemic tissue (reperfusion), additional injury can occur. This ischaemia-reperfusion (I/R) injury is driven by the production of reactive oxygen species, activation of inflammatory pathways, and endothelial dysfunction. These processes lead to cell death, microvascular dysfunction, and can even affect remote organs, contributing to multiple organ dysfunction syndrome. The inflammatory response involves leukocyte adhesion, increased vascular permeability, and the release of cytokines and other mediators 57.
Mitochondrial Dysfunction and Oxidative Stress
Mitochondria play a central role in the pathogenesis of ischaemic diseases. During ischaemia and reperfusion, mitochondrial dysfunction leads to increased production of reactive oxygen species, which can damage cellular components and trigger apoptosis. Genetic and epigenetic factors affecting mitochondrial function are increasingly recognized as contributors to both ischaemic heart disease and stroke .
Pathophysiology in Other Organs: Kidney and Brain
Ischaemic injury is not limited to the heart. In the kidneys, ischaemia leads to acute kidney injury through hemodynamic disturbances, endothelial and epithelial cell injury, and a strong pro-inflammatory response. This can result in both immediate and long-term impairment of renal function .
In the brain, ischaemic stroke triggers a series of damaging events, including excitotoxicity, inflammation, and apoptosis, particularly in the area surrounding the core of the infarct (the penumbra). Capillary dysfunction leads to brain oedema, which progresses through distinct phases and can result in haemorrhagic transformation if severe 610.
Adaptive and Protective Mechanisms
The body has some natural protective mechanisms against ischaemic injury. Ischaemic preconditioning, where brief episodes of ischaemia make tissues more resistant to subsequent prolonged ischaemia, involves complex signaling pathways and changes in protein synthesis. These adaptive responses can reduce the extent of injury if triggered appropriately .
Conclusion
Ischaemic disease pathophysiology is complex and involves a combination of vascular, cellular, and molecular mechanisms. Both macrovascular and microvascular dysfunction contribute to disease in the heart, while similar processes underlie ischaemic injury in other organs like the kidney and brain. Key features include the ischaemic cascade, inflammatory responses, mitochondrial dysfunction, and adaptive mechanisms such as preconditioning. Understanding these processes is essential for developing effective treatments and improving outcomes in patients with ischaemic diseases 1234+6 MORE.
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