动脉粥样硬化课件_8.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 动脉内膜或中膜发生非炎症性?、退化性和?增生性病变，导致管壁增厚变硬、失去弹性和管腔狭窄为共同特点的动脉病变。一般分为动脉粥样硬化、小动脉硬化和动脉中层钙化3种类型。它们的病因、发病?、病理过程及对机体的损害有很大的不同??，?其中以动脉粥样硬化为此病中最常见和重要。相当多的中年人因动脉粥样硬化引起严重的疾病如冠心病等，为老年人主要的死亡原因之一。小动脉硬化为小型动脉弥漫性增生性病变，其发生、发展与高血压及糖尿病有关，病变发展到一定阶段，即可引起多脏器功能障碍，对患者也具有极大的危害。动脉中层钙化不如前面两种多见，主要累及中型动脉，常见于四肢动脉尤其昌下肢动脉搏，引起管壁中层变质钙化，多不产生明显症状，其临床意义不大。???动脉壁由内膜、中膜和外膜组成，按管径大小，可分为大、中、小三级，大动脉如主动脉及其大分支的中膜含有大量弹力纤维，弹性大，也称为弹力型动脉；中动脉如冠状动脉、脑动脉、肾动脉和四肢动脉等，中层富含平滑肌，也称为肌型动脉；小动脉指管径在1毫米以下的动脉?，也属于肌型动脉，但内弹力膜薄而不明显，中膜的平滑肌亦很薄。 * * * * Atherosclerotic plaque has 2 main components: a soft, lipid-rich core and a hard, collagen-rich fibrous cap. In stable plaques, a thick fibrous cap may represent 70% of plaque volume. It stabilizes the plaque and prevents it from undergoing rupture. In contrast, unstable plaque has a thin fibrous cap and is at greater risk for rupture. In unstable plaque, the lipid-rich core may represent the majority of the plaque volume. The core is rich in extracellular lipids, which are formed by trapping blood-derived lipids, notably low-density lipoprotein, or by lipid-filled macrophages, known as foam cells. The plaque destabilizes due to inflammation by foam cells and other inflammatory mediators that make the plaque more vulnerable to rupture. This commonly occurs at the junction of the plaque and the less diseased vessel wall. As a result, the lipid core may be exposed to flowing blood leading to platelet-mediated thrombus formation. Falk reviewed the work of other investigators regarding the severity of stenosis and its association with the risk of MI. Results showed that 86% of MIs resulted from lesions that were 70% stenosed. Most experts prior to Falk thought that patients had heart attacks because of blockages that increased in size until they blocked the blood vessel and caused a heart attack.1 Based on the findings of Falk, we now know the primary cause of a heart attack is the rupture of unstable p