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INTRODUCTION

Key Clinical Questions

  • image What is the optimal care and management of patients with ST-segment elevation myocardial infarction?

  • image What is the optimal care and management of patients with non-ST segment elevation acute coronary syndrome?

The term acute coronary syndrome (ACS) refers to the spectrum clinical presentations related to acute myocardial ischemia or infarction due to the abrupt reduction in coronary blood flow. ACS is divided into ST-segment elevation myocardial infarctions (STEMIs) and non-ST segment elevation acute coronary syndromes (NSTE-ACSs). The NSTE-ACS is further subdivided on the basis of elevated cardiac biomarkers of myocardial necrosis. Patients with elevated cardiac biomarkers are defined as non-ST segment elevation myocardial infarction (NSTEMI) and those without elevated biomarkers are termed unstable angina (UA).

This chapter will focus on the diagnosis, risk stratification, and treatment of patients with ACS based on the American College of Cardiology Foundation and American Heart Association (ACCF/AHA) practice guidelines for STEMI and NSTE-ACS. All guideline recommendations will be cited in this chapter and referenced according the American College of Cardiology Foundation/American Heart Association classification scheme (Table 128-1).

Table 128-1ACCF/AHA Classification of Recommendations and Level of Evidence

EPIDEMIOLOGY & PATHOPHYSIOLOGY

ACS is common, with over 780,000 patients experiencing an ACS event every year in the United States. Of these events, approximately 70% are classified as NSTE-ACS. ACS is related to an acute imbalance of myocardial oxygen consumption and demand, usually related to a sudden coronary artery obstruction. Autopsy studies suggest that most ACS events are related to acute coronary thrombosis, with acute plaque rupture being the most common etiology. The atherosclerosis at sites of plaque rupture is characterized by large lipid-laden necrotic cores overlying a disrupted thin fibrous cap. The second most common cause of acute coronary thrombosis is plaque erosion, characterized by thrombus formation at an area of denuded endothelium. These plaques are characterized by ...

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