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Acute Coronary Syndromes: Non ST Elevation MI (ACS:NSTEMI)
Vidya S. Banka, MD, is director of interventional cardiology at Pennsylvania Hospital, and clinical professor of medicine at the University of Pennsylvania School of Medicine. Here, he discusses non-ST elevation myocardial infarction. The author has no relationships with commercial interests related to the content of this lecture. The author notes that ischemic heart disease is the most prevalent cardiovascular disorder in the United States, affecting some 213 persons/100,000 population. Non-ST elevation acute coronary syndromes can be subdivided into non-ST elevation MI (NSTEMI); and unstable angina. This lecture outlines the definitions, pathophysiology, diagnostic parameters, and therapeutic approaches to the NSTEMI syndromes. While unstable angina lacks precise definitions, the Canadian Cardiovascular Society has developed a classification system to grade anginal symptoms. There is also Braunwald's classification for unstable angina. The author discusses the prognosis for unstable angina, the role of macrophages, and the electrical and biochemical markers of myocardial injury. So far as management and early intervention are concerned, recent guidelines of the American College of cardiology and the American Heart Association recommend an early invasive approach in high-risk patients with acute coronary syndromes. The lecture describes the ICTUS trial involving 1200 high-risk patients with acute coronary syndromes without ST segment elevation but with a positive Troponin at entry. The introduction of IIb and IIIa receptor antagonists has offered a major advance in the management of acute coronary syndrome. Although their primary use has been during percutaneous coronary intervention procedures, more recently Eptifibatide and Tirofiban have been approved in the US for management of patients with non-ST elevation MI. Medical therapy in unstable angina/acute coronary syndromes with NSTEMI is to reduce prothrombotic/procoagulant effects in order to prevent total coronary occlusion and to provide improved myocardial blood flow by using coronary vasodilator agents to achieve these effects. The main treatment remains unfractionated or low molecular weight heparin and such antiplatelet agents as aspirin, for which there is strong evidence that it reduces the risk of myocardial infarction. The lecture continues with a discussion of low molecular weight heparin versus unfractionated heparin, a topic covered in a previous lecture on ST elevation myocardial infarction. The lecture concludes with a description of three acronymic trials – PURSUIT, PRISM, and CURE. |
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