Acute Myocardial Infarction（AMI）.pptVIP

Acute Myocardial Infarction Willis E. Godin, D.O. Acute Myocardial Infarction Despite vigorous attempts at population risk factor modification and primary prevention of arteriosclerosis, the incidence of hospitalization for myocardial infarction (MI) is increasing slightly Annually 1.7 million to 2 million admissions to US hospitals are for the evaluation of acute chest pain, and only 30% of patients admitted ultimately are found to have unstable angina or MI. Acute Myocardial Infarction Patients with acute myocardial infarction who are mistakenly discharged from the emergency department have short-term mortality rates of about 25 percent, at least twice what would be expected if they were admitted However, the admission of a patient with chest pain who is at low risk for acute myocardial infarction costs an average of $2,000 to $5,000 at many institutions and can lead to unnecessary tests and procedures, with their attendant costs and complications. Coronary Occlusion Gradual occlusion is caused by plaque disruption and mural thrombosis with extracellular matrix deposition, followed by healing and smooth-muscle proliferation. Thick stable plaques are least likely to rupture are more calcified. Acute Coronary Occlusion Sudden total or near-total arterial occlusion frequently develops in arteries that previously appeared to have minimal stenosis. Two thirds of arteries with plaques that rupture and in which a totally occlusive thrombus subsequently develops have stenosis of 50 percent or less before plaque rupture, and in 97 percent of patients, stenosis is initially less than 70 percent. Most infarctions are now thought to occur not at the site of a gradually narrowing chronic stenosis but rather in areas generally considered to not limit flow at rest, the junction of the plaque cap and the adjacent normal intima or the shoulder regions of the lipid pool Plaque composition Mature plaques are made up of two main components: a lipid-rich core and a meshwork of extra