- Infarction
- The formation of an infarct, an area of tissue death due to a local lack of oxygen. For example, in a myocardial infarction there is death of myocardial (heart muscle) tissue due to sudden (acute) deprivation of circulating blood. This is usually caused by arteriosclerosis with narrowing of the coronary arteries, the culminating event being a thrombosis (clot). Aside from designating the process of forming the infarct, infarction is synonymous with the infarct itself. The word "infarction" comes from the Latin "infarcire" meaning "to plug up or cram." It refers to the clogging of the artery.See also infarct.
* * *1. Sudden insufficiency of arterial or venous blood supply due to emboli, thrombi, mechanical factors, or pressure that produces a macroscopic area of necrosis; any organ can be affected. 2. SYN: infarct.- anterior myocardial i. i. involving the anterior wall of the left ventricle, and producing indicative electrocardiographic changes in the anterior chest leads and often in limb leads, I and aVL.- anteroinferior myocardial i. i. involving both anterior and inferior walls of the heart simultaneously.- anterolateral myocardial i. extensive anterior i. producing indicative changes across the precordium, often also on leads I and aVL.- anteroseptal myocardial i. an anterior i. in which indicative electrocardiographic changes are confined to the medial chest leads (V1–V4).- apical i. SYN: inferolateral myocardial i..- cardiac i. SYN: myocardial i..- inferior myocardial i. i. in which the inferior or diaphragmatic wall of the heart is involved, producing indicative changes in leads II, III, and aVF in the electrocardiogram. SYN: diaphragmatic myocardial i..- inferolateral myocardial i. i. involving the inferior and lateral surfaces of the heart and producing indicative changes in the electrocardiogram in leads II, III, aVF, V5, and V6. SYN: apical i..- lateral myocardial i. i. involving only the lateral wall of the heart, producing indicative electrocardiographic changes confined to leads I, aVL, or V5 and V6.- myocardial i. (MI) i. of an segment of the heart muscle, usually as a result of occlusion of a coronary artery. SYN: cardiac i., heart attack.Myocardial i. is the most common cause of death in the U.S. About 800,000 people annually sustain first heart attacks, with a mortality rate of 30%, and 450,000 people sustain recurrent heart attacks, with a mortality rate of 50%. The most common cause of MI is thrombosis of an atherosclerotic coronary artery. Less common causes are coronary artery anomalies, vasculitis, or spasm induced by cocaine, ergot derivatives, or other agents. Risk factors for MI include male gender, family history of MI, obesity, hypertension, cigarette smoking, and elevation of total cholesterol, LDL cholesterol, homocysteine, lipoprotein (a), or C-reactive protein. At least 80% of MIs occur in people without a prior history of angina pectoris, and 20% are not recognized, either because they cause no symptoms (silent i.) or because symptoms are attributed to other causes. Some 20% of people sustaining MI die before reaching a hospital. The classical symptom of MI is crushing anterior chest pain radiating into the neck, shoulder, or arm, lasting more than 30 minutes, and not relieved by nitroglycerin; typically pain is accompanied by dyspnea, diaphoresis, weakness, and nausea. Significant physical findings, often absent, include an atrial gallop rhythm (4th heart sound) and a pericardial friction rub. The electrocardiogram shows ST segment elevation (later changing to depression) and T wave inversion in leads reflecting the area of i.. Q waves indicate transmural damage and a poorer prognosis. Diagnosis is supported by acute elevation in serum levels of CK-MB, lactic dehydrogenase, the myoglobin isoenzyme of creatine kinase, and troponins. Unequivocal evidence of MI may be lacking during the first 6 hours in as many as 50% of patients. Death from acute MI is usually due to arrhythmia (ventricular fibrillation or asystole), shock (forward failure), congestive heart failure, or papillary muscle rupture. Other grave complications, which may occur during convalescence, include cardiorrhexis, ventricular aneurysm, and mural thrombus. Acute MI is treated (ideally under continuous ECG monitoring in the intensive care or coronary care unit of a hospital) with narcotic analgesics, oxygen by inhalation, intravenous administration of a thrombolytic agent, antiarrhythmic agents when indicated, and usually anticoagulants (aspirin, heparin), beta-blockers, and ACE inhibitors. Patients with evidence of persistent ischemia require angiography and may be candidates for balloon angioplasty. Data from the Framingham Heart Study show that a higher percentage of acute MIs are silent or unrecognized in women and the elderly. Several studies have shown that women and the elderly tend to wait longer before seeking medical care after the onset of acute coronary symptoms than men and younger persons. In addition, women seeking emergency treatment for symptoms suggestive of acute coronary disease are less likely than men with similar symptoms to be admitted for evaluation, and women are less frequently referred than are men for diagnostic tests such as coronary angiography. Other studies have shown important gender differences in the presenting symptoms and medical recognition of MI. Chest pain is the most common symptom reported by both men and women, but men are more likely to complain of diaphoresis, while women are more likely to experience neck, jaw, or back pain, nausea, vomiting, dyspnea, or cardiac failure, in addition to chest pain. The incidence rates of acute pulmonary edema and cardiogenic shock in MI are higher in women, and mortality rates at 28 days and 6 months are also higher.- nontransmural myocardial i. (NTMI) necrosis of heart muscle that fails to extend from the endocardium completely to the epicardium, often erroneously considered relatively benign.- posterior myocardial i. i. involving the posterior wall of the heart; also formerly used erroneously of infarctions involving the inferior or diaphragmatic surface of the heart.- silent myocardial i. i. that produces none of the characteristic symptoms and signs of myocardial i..- subendocardial myocardial i. i. that involves only the layer of muscle subjacent to the endocardium.- transmural myocardial i. i. that involves the whole thickness of the heart muscle from endocardium to epicardium. SYN: through-and-through myocardial i..- watershed i. cortical i. in an area where the distribution of major cerebral arteries meet or overlap.
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in·farc·tion in-'färk-shən n1) the process of forming an infarct <severe stress sometime between the 5th and 20th days after \infarction (Jour. Amer. Med. Assoc.)>* * *
n.the death of part or the whole of an organ that occurs when the artery carrying its blood supply is obstructed by a blood clot (thrombus) or an embolus. For example, myocardial infarction, affecting the muscle of the heart, follows coronary thrombosis. A small localized area of dead tissue produced as a result of an inadequate blood supply is known as an infarct.* * *
in·farc·tion (in-fahrkґshən) 1. infarct. 2. the formation of an infarct.
Medical dictionary. 2011.
