急性心肌梗死AMI诊断和治疗进展(英文课件.ppt

Acute Myocardial InfarctionDEFINITION Acute myocardial infarction (MI) is defined as death or necrosis of myocardial cells. It is a diagnosis at the end of the spectrum of myocardial ischemia or acute coronary syndromes. Myocardial infarction occurs when myocardial ischemia exceeds a critical threshold and overwhelms myocardial cellular repair mechanisms that are designed to maintain normal operating function and hemostasis. Ischemia at this critical threshold level for an extended time period results in irreversible myocardial cell damage or death.1-3DEFINITION (Cntd.)Myocardial infarction can be subcategorized on the basis of anatomic, morphologic, and diagnostic clinical information. From an anatomic or morphologic standpoint, the two types of MI are transmural and nontransmural. A transmural MI is characterized by ischemic necrosis of the full thickness of the affected muscle segment(sIn a nontransmural MI, the area of ischemic necrosis is limited to either the endocardium or the endocardium and myocardium. The presence or absence of Q waves does not distinguish a transmural from a non-transmural MI as determined by pathology.4DEFINITION (Cntd. II)A more common clinical diagnostic classification scheme is also based on ECG findings as a means of distinguishing between two types of MIone that is marked by ST elevation STEMIand one that is not NSTEMIThe distinction between an ST-elevation MI and a non-ST-elevation MI also does not distinguish a transmural from a non-transmural MI. The presence of Q waves or ST segment elevation is associated with higher early mortality and morbidity; ACS TypesPREVALENCE In general, MI can occur at any age, but its incidence rises with age. The actual incidence is dependent upon predisposing risk factors for atherosclerosis, which are discussed below. Approximately 50% of all MIs in the US occur in people younger than 65 years of age. However, in the future, as demographics shift and the mean age of the population increases, a larger percentage of patients presenting with MI will be older than 65 years DIAGNOSIS Identifying a patient who is currently experiencing a MI can be extremely straightforward, very difficult, or somewhere in between. A straightforward diagnosis of MI can usually be made in patients who have a number of atherosclerotic risk factors along with the presence of symptoms consistent with a lack of blood flow to the heart. Patients who suspect that they are having a MI usually present to an emergency department. Once a patients clinical picture raises a suspicion of a MI, several confirmatory tests can be performed rapidly. These tests include ECG, blood testing, and echocardiography. HistoryPRODROMAL SYMPTOMS:history remains of substantial value in establishing a diagnosis. Resembles classic angina pectoris but it occurs at rest or with less activity than usual and can therefore be classified as unstable angina. Of the patients with AMI presenting with prodromal symptoms of unstable angina, approximately one third have had symptoms from 1 to 4 weeks before hospitalization; in the remaining two thirds, symptoms predated admission by 1 week or less, with one third of these patients having had symptoms for 24 hours or less. SIGNS AND SYMPTOMSAcuteMI may have unique presentations in individual patients. The degree of symptoms ranges from none at all to sudden cardiac death. An asymptomatic MI is not necessarily less severe than a symptomatic event; but patients who experience asymptomatic MIs are more likely to be diabetic. Chest pain described as a pressure sensation, fullness, or squeezing in the midportion of the thorax Radiation of chest pain into the jaw/teeth, shoulder, arm, and/or back Associated dyspnea or shortness of breath Associated epigastric discomfort with or without nausea and vomiting Associated diaphoresis or sweating Syncope or near-syncope without other cause Impairment of cognitive function without other cause A MI may occur at any time of the day, but most appear to be clustered around the early hours of the morning and/or are associated with demanding physical activity. Approximately 50% of patients have some warning symptoms (angina pectoris or an anginal equivalent) prior to the infarct.4Nature of PainThe pain of AMI is variable in intensity; in most patients it is severe and in some instances intolerable. The pain is prolonged, usually lasting for more than 30 minutes and frequently for a number of hours. Described as constricting, crushing, oppressing, or compressing; often the patient complains of a sensation of a heavy weight or a squeezing in the chest. Although the discomfort is typically described as a choking, viselike, or heavy pain, it may also be characterized as a stabbing, knifelike, boring, or burning discomfort. The pain is usually retrosternal in location, spreading frequently to both sides of the anterior chest, with predilection for the left side. Often the pain radiates down the ulnar aspect of the left arm, produc。