الفهرس | Only 14 pages are availabe for public view |
Abstract Summary Acute coronary syndrome (ACS) is a syndrome (set of signs and symptoms) due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies. The most common symptom is chest pain which often radiating to the left shoulder or angle of the jaw, crushing, central and associated with nausea and sweating. Acute coronary syndrome is usually caused by one of three problems: ST elevation myocardial infarction (STEMI, 30%), non ST elevation myocardial infarction (NSTEMI, 25%), or unstable angina (38%). Acute myocardial infarction (AMI) indicates irreversible myocardial injury resulting in necrosis of a significant portion of myocardium (generally >1 cm). Atherosclerosis is the most common cause of myocardial infarction and its major risk factors are hyperlipidemia, diabetes, smoking, hypertension, gender and age. Endothelial dysfunction and inflammation have a major role in the initiation of the atherosclerotic plaque formation. Myocardial infarction occurs most often in the early morning hours. Mechanisms that may explain this circadian variation include morning increase in sympathetic tone and plasma catecholamine leading to increases in blood pressure, heart rate, coronary vascular tone, and myocardial contractility resulting in increased myocardial demand. |