Chapter 013. Chest Discomfort (Part 7)

Unpublished data from Brigham and Womens Hospital Chest Pain Study, 1997–1999Markers of myocardial injury are often obtained in the emergency department evaluation of acute chest discomfort. The most commonly used markers are creatine kinase (CK), CK-MB, and the cardiac troponins (I and T). Rapid bedside assays of the cardiac troponins have been developed and shown to be sufficiently accurate to predict prognosis and guide management. Some data support the use of other markers, such as serum myoglobin, C-reactive protein (CRP), placental growth factor, myeloperoxidase, and B-type natriuretic peptide (BNP); their roles are the subject of ongoing research. Single values...
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Chapter 013. Chest Discomfort (Part 7) Chapter 013. Chest Discomfort (Part 7) Unpublished data from Brigham and Womens Hospital Chest Pain Study,1997–1999 Markers of myocardial injury are often obtained in the emergencydepartment evaluation of acute chest discomfort. The most commonly usedmarkers are creatine kinase (CK), CK-MB, and the cardiac troponins (I and T).Rapid bedside assays of the cardiac troponins have been developed and shown tobe sufficiently accurate to predict prognosis and guide management. Some datasupport the use of other markers, such as serum myoglobin, C-reactive protein(CRP), placental growth factor, myeloperoxidase, and B-type natriuretic peptide(BNP); their roles are the subject of ongoing research. Single values of any ofthese markers do not have high sensitivity for acute myocardial infarction or forprediction of complications. Hence, decisions to discharge patients home shouldnot be made on the basis of single negative values of these tests. Provocative tests for coronary artery disease are not appropriate for patientswith ongoing chest pain. In such patients, rest myocardial perfusion scans can beconsidered; a normal scan reduces the likelihood of coronary artery disease andcan help avoid admission of low-risk patients to the hospital. Promising earlyresults suggest that 64-slice CT and cardiac MRI may be of sufficient accuracy fordiagnosis of coronary disease that these technologies may become widely used forpatients with acute chest pain in whom the diagnosis is not clear. Clinicians frequently employ therapeutic trials with sublingualnitroglycerin or antacids or, in the stable patient seen in the office setting, a protonpump inhibitor. A common error is to assume that a response to any of theseinterventions clarifies the diagnosis. While such information is often helpful, thepatients response may be due to the placebo effect. Hence, myocardial ischemiashould never be considered excluded solely because of a response to antacidtherapy. Similarly, failure of nitroglycerin to relieve pain does not exclude thediagnosis of coronary disease. If the patients history or examination is consistent with aortic dissection,imaging studies to evaluate the aorta must be pursued promptly because of thehigh risk of catastrophic complications with this condition. Appropriate testsinclude a chest CT scan with contrast, MRI, or transesophageal echocardiography. Acute pulmonary embolism should be considered in patients withrespiratory symptoms, pleuritic chest pain, hemoptysis, or a history of venousthromboembolism or coagulation abnormalities. Initial tests usually include CTangiography or a lung scan, which are sometimes combined with lower extremityvenous ultrasound or D-dimer testing. If patients with acute chest discomfort show no evidence of life-threateningconditions, the clinician should then focus on serious chronic conditions with thepotential to cause major complications, the most common of which is stableangina. Early use of exercise electrocardiography, stress echocardiography, orstress perfusion imaging for such patients, whether in the office or the emergencydepartment, is now an accepted management strategy for low-risk patients.Exercise testing is not appropriate, however, for patients who (1) report pain thatis believed to be ischemic occurring at rest or (2) have electrocardiographicchanges not known to be old that are consistent with ischemia. Patients with sustained chest discomfort who do not have evidence for life-threatening conditions should be evaluated for evidence of conditions likely tobenefit from acute treatment (Table 13-3). Pericarditis may be suggested by thehistory, physical examination, and ECG (Table 13-2). Clinicians should carefullyassess blood pressure patterns and consider echocardiography in such patients todetect evidence of impending pericardial tamponade. Chest x-rays can be used toevaluate the possibility of pulmonary disease. Guidelines and Critical Pathways for Acute Chest Discomfort Guidelines for the initial evaluation for patients with acute chest pain havebeen developed by the American College of Cardiology, American HeartAssociation, and other organizations. These guidelines recommend performance ofan ECG for virtually all patients with chest pain who do not have an obviousnoncardiac cause of their pain, and performance of a chest x-ray for patients withsigns or symptoms consistent with congestive heart failure, valvular heart disease,pericardial disease, or aortic dissection or aneurysm. The American College of Cardiology/American Heart Associationguidelines on exercise testing support its use in low-risk patients presenting to theemergency d ...