Common use of Mechanisms of myocardial damage Clause in Contracts

Mechanisms of myocardial damage. The severity of an AMI is dependent on three factors: the level of the occlusion in the coronary artery, the length of time of the occlusion, and the presence or absence of collateral circulation. In general, the more proximal the coronary occlusion, there is a greater risk of an increased area of necrosis. The larger the AMI, the chance of death due to a mechanical complication or pump failure increases. In addition, the longer the time period of vessel occlusion, there is a greater chance of irreversible myocardial damage distal to the occlusion. The death of myocardial cells first occurs in the area of myocardium that is most distal to the arterial blood supply, the endocardium. As the duration of the occlusion increases, the area of myocardial cell death enlarges, extending from the endocardium to the myocardium and ultimately to the epicardium. The area of myocardial cell death then spreads laterally to areas of watershed or collateral perfusion. The extent of myocardial cell death defines the magnitude of the AMI. If blood flow can be restored to at-risk myocardium, more heart muscle can be saved from irreversible damage or death. The ischemic zone will undergo inflammatory necrotic changes, and the myocardial tissue will eventually be completely replaced by fibrous infarct tissue. In the early stages after an AMI, the damage causes deterioration of cardiac muscle contractility and structural integrity. This results in thinning of the walls of the heart, which can have severe consequences including rupture at the site, expansion of the area of damage, and the formation of blood clots. After some weeks or months, this can evolve to dilatation of the heart, which further reduces its ability to pump blood efficiently, resulting in heart failure.