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Learn the differential diagnosis of ischemic chest pain and the laboratory tests used in the assessment of myocardial injury, including acute myocardial infarction.
Learn the clinical features of congestive heart failure (CHF) and the laboratory tests useful in ruling in and ruling out CHF and monitoring and risk outcomes assessment of patients with this disorder.
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There are many forms of cardiac disease. This chapter briefly covers the role of biomarkers in acute myocardial infarction (AMI) and congestive heart failure (CHF). The large numbers of other cardiac diseases are not discussed in this chapter because of the relatively minor role of diagnostic clinical laboratory tests in these disorders.
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Acute Myocardial Infarction
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The term AMI is defined as an imbalance between myocardial oxygen supply (ischemia) and demand, resulting in injury to and the eventual death of myocytes. AMI should be used when there is evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischemia. Such necrosis is most often associated with a thrombotic occlusion superimposed on coronary atherosclerosis. It is now apparent that the process of plaque rupture and thrombosis is 1 of the ways in which coronary atherosclerosis progresses. Total loss of coronary blood flow results in a clinical syndrome associated with an ST-segment elevation MI (STEMI). Partial loss of coronary perfusion, if severe, can lead to necrosis as well, which is generally less severe and is known as non-ST-segment elevation MI (NSTEMI). Both STEMI and NSTEMI are considered type 1 MIs. In instances of myocardial injury with necrosis with a condition other than coronary artery disease (CAD), which contributes to an imbalance between oxygen supply and/or demand (eg, coronary endothelial dysfunction, respiratory failure, hypotension, etc), this MI is a type 2 MI that is secondary to ischemic imbalance. Other ischemic events of lesser severity without myocardial necrosis are designated as angina, which can range from stable to unstable. About 1.7 million patients are hospitalized each year in the United States with an acute coronary syndrome (ACS). Approximately 700,000 patients suffer from an initial AMI annually and another 500,000 from a recurrent AMI. Coronary heart disease causes 20% of all deaths and cardiovascular diseases up to 40%. Historically, most deaths caused by ischemic heart disease have been acute, but as our therapeutic abilities have improved, the disease is slowly becoming a more chronic one.
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In many patients with AMI, no precipitating factor can be identified. The clinical history remains of substantial value in establishing a diagnosis. A prodromal history of angina can be elicited in 40% to 50% of patients with AMI. Of the patients with AMI presenting with prodromal symptoms, approximately one third have had symptoms from 1 to 4 weeks before hospitalization; in the remaining two thirds, symptoms predate admission by a week or less, with one third having had ...