Coronary heart disease (CHD) is a worldwide health epidemic. In the United States, for example, it is estimated that 13.7 million Americans have CHD, including more than 7.2 million individuals who already have had a myocardial infarction (MI).1 In the group of persons older than 30 years of age, 213 per 100,000 individuals have CHD.1 Although age-specific events related to CHD have fallen dramatically in the last few decades, the overall prevalence has risen as populations age and patients survive the initial coronary or cardiovascular event. The Centers for Disease Control and Prevention estimates that life expectancy in America might be increased by 7 years if CHD and its complications were eradicated.2 Worldwide, 30% of all deaths can be attributed to cardiovascular disease, of which more than half are caused by CHD, and the forecasts for the future estimate a growing number as a consequence of lifestyle changes in developing countries.2 Globally, of those dying from cardiovascular diseases, 80% are in developing countries and not in the Western world.2
CHD represents a continuum of disease pathologies and its subsequent risks. CHD has been classified as chronic CHD, acute coronary syndromes, and sudden death. CHD may present clinically in many ways, extending from an asymptomatic finding to unexpected cardiac collapse. Chronic CHD is always secondary to coronary atherosclerosis, leading to mismatch of coronary blood flow and adenosine triphosphate homeostasis (imbalance of supply and demand) and a stable pattern of coronary ischemia. The clinical pattern includes stable angina pectoris and myocardial hibernation.3 This chapter, however, focuses on a more high-risk population, those with acute coronary syndromes.
Acute coronary syndrome (ACS) is a unifying term representing a common end result, acute myocardial ischemia. Acute ischemia is usually, but not always, caused by atherosclerotic plaque rupture, fissuring, erosion, or a combination with superimposed intracoronary thrombosis and is associated with an increased risk of cardiac death and myonecrosis.4 It encompasses acute MI (resulting in ST-segment elevation or non–ST-segment elevation) and unstable angina. Recognizing a patient with ACS is important because the diagnosis triggers both triage and management. Those deemed to have an acute coronary syndrome in the emergency department should be triaged immediately to an area with continuous electrocardiographic monitoring and defibrillation capability. An electrocardiogram (ECG) should be obtained and accurately interpreted within 10 minutes. Those patients with suspected ACS should be managed immediately with antiplatelet and anticoagulant therapies and considered for immediate revascularization mechanically or pharmacologically if new ST-segment elevation is noted.5
Because of the life-threatening nature of an ACS, it is prudent to have a low threshold in suspecting a patient with acute chest pain as potentially having an ACS. Because the efficient diagnosis and optimal management of these patients are derived from information mostly only readily available from initial clinical presentation, there is overlap of those with true ACS and those who ultimately do not have CHD as a cause of their ...