الفهرس 
Pathogenesis of Acute Coronary SyndromePathogenesis Syndromes
B-Invasive Imaging of the Coronary AnatomyOnly 14 pages are availabe for public view
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Abstract
Acute coronary syndromes is an umbrella term used to cover any group of clinical symptoms compatible with acute myocardial ischemia which extend from acute myocardial infarction through minimal myocardial injury to unstable angina. Acute myocardial ischemia is chest pain due to insufficient blood supply to the heart muscle that results from coronary artery disease. Acute coronary syndromes encompass a spectrum of coronary artery diseases, including unstable angina, STEMI, NSTEMI.
The arterial supply of the heart is provided mainly by the left coronary artery and right coronary artery. The components of the normal vessel wall are arranged into three layers which include from inside to outside; intima, media, and adventia.
The risk factors for ACS include dyslipidemia, smoking, hypertension, diabetes, obesity, metabolic syndrome, sedentary life style, inflammations, homocysteinemia, and NSAIDS. Acute coronary syndromes are most often due to atherosclerotic plaques, which reduce the blood supply to a portion of the myocardium. However there are uncommon conditions that precipitate myocardial ischemia such as coronary spasm.
Disruption of an atherosclerotic fibrofatty plaque that is accompanied with thrombosis and vasoconstriction is responsible for varying degrees of coronary obstruction leading to unstable angina, and NSTEMI if there is a partial obstruction or STEMI if there is a complete obstruction.
The typical clinical presentation of ACS is retro-sternal pressure or heaviness radiating to the left arm, neck, or jaw, which may be intermittent (usually lasting several minutes) or persistent. These complaints may be accompanied by other symptoms such as diaphoresis, nausea, abdominal pain, dyspnea, and syncope. However, atypical presentations of ACS are not uncommon which include epigastric pain, recent-onset indigestion, stabbing chest pain, chest pain with some pleuritic features, or increasing dyspnea.
The physical examination is frequently normal. Signs of heart failure or haemodynamic instability may be the presenting findings. Physical findings such as pallor, increased sweating, or tremor may orientate towards precipitating conditions, such as anaemia and thyrotoxicosis.
ECG is the first-line diagnostic tool in the assessment of patients with suspected ACS. ECG changes in ACS may be ST-segment elevation, ST-segment depression, or T-wave inversion. A completely normal ECG does not exclude the possibility of ACS.
Other non invasive imaging studies of the heart may include chest radiograph, radionuclide myocardial perfusion imaging, Technetium-99m (99mTc) tetrofosmin single-photon emission computed tomography, resting cardiac magnetic resonance imaging, and dual-source 64-slice CT scanners.
Several biomarkers have been investigated to be used for diagnostic and risk assessment, such as the markers of myocardial cell injury which include troponin I, CK-MB, or myoglobin, myeloperoxidase, and ischemia modified albumin.
Acute coronary syndromes must be differentiated from the other cardiac causes of chest pain such as pericarditis, myocrditis, dilated cardiomyopathy, aortic stenosis, aortic dissection, hypertensive emergencies, or cardiac tamponade, and noncardiac causes of chest pain such as tension pneumothorax, pulmonary empolism, esophageal spasm, acute gastritis, gastroesophageal reflux disease, acute cholecystitis, bronchial asthma, or anxiety.
The initial management of patients with acute coronary syndromes includes a series of routine measures such as oxygen therapy, morphine sulfate, aspirin, clopidogrel, nitroglycerin, beta blocker, calcium channel blockers, angiotensin-converting enzyme inhibitors, anticoagulants, strict glucose control, and statins.
Choice of treatment strategy for patients with NSTEACS is based on risk stratification. Low-risk patients are initially managed by conservative treatment. Patients with intermediate-risk should undergo further assessment to allow reclassification into low-risk or high-risk categories. Patients with high-risk are best managed with aggressive medical therapy such as glycoprotein IIb/IIIa receptor inhibitors and invasive therapy such as coronary angiography and coronary revascularization.
Reperfusion therapy may be obtained with fibrinolytic therapy, PCI, or CABG surgery for management of patients with STEMI unless they are contraindicated.
Long term medical therapy include antiplatelet agents, beta blockers, low-density cholesterol lowering agents, inhibitors of the renin-angiotensin aldosterone system, nitroglycerin, calcium channel blockers, and treatment of major risk factors such as hypertension, smoking, dyslipidemia, and diabetes mellitus.
Complications of ACS include cardiogenic shock, rupture of interventricular septum, papillary muscle rupture, ventricular aneurysm, dysrrhythmia, conduction problems, blood clots, postprocedure chest pain, acute mitral regurgitation, pericarditis, right ventricular infarction, and recurrent ischemia.
Morbidity and mortality rates are high in young ACS patients, single living, and atypical clinical presentations. The initial therapeutic strategy is strongly related to long-term prognosis. A number of risk assessment tools such as the TIMI have been developed to assist in assessing the risk of death and ischemic events in patients with ACS.