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Pathophysiology of Acute Coronary Syndrome
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* in most of ACS cases syndrome occurs when an
atherosclerotic plaque ruptures, fissures or ulcerates and precipitates thrombus formation. This
results in sudden total or near-total arterial occlusion. Alternatively thrombus may break off from
a ruptured plaque and occlude smaller vessels like coronary arteries.
* systemic factors and inflammation also play role in changing haemostatic
and coagulation pathways and may play a part in the initiation of the intermittent thrombosis that
is a characteristic of unstable angina. Inflammatory acute phase proteins, cytokines, chronic
infections and catecholamine surges may enhance production of tissue factor, procoagulant activity
or platelet hyperaggregability.
* in the case of Q wave Mycardial infarction results in a spreading area of
necrosis that reaches epicardium in 4-6 hours – full thickness infarction
* in rare cases may be due to coronary artery occlusion by embolism, congenital
abnormalities, coronary artery spasm and a wide variety of systemic (particularly inflammatory)
diseases
* initially infarcted muscle is softened leading to an increase in ventricular
compliance but, as fibrosis takes place, compliance of heart muscles decreases
* poor correlation between angiographic severity of coronary stenosis and chance
of acute occlusion
* Other causes of reduced myocardial blood flow include mechanical obstruction
(e.g. air embolus), dynamic obstruction (e.g. vessel spasm), and infection or
inflammation.
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