Chapter 013. Chest Discomfort (Part 7)

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Unpublished data from Brigham and Women's Hospital Chest Pain Study, 1997–1999 Markers of myocardial injury are often obtained in the emergency department evaluation of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 Chest Discomfort (Part 7) Unpublished data from Brigham and Women's Hospital Chest Pain Study, 1997–1999 Markers of myocardial injury are often obtained in the emergency department evaluation of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 of any of these markers do not have high sensitivity for acute myocardial infarction or for prediction of complications. Hence, decisions to discharge patients home should not be made on the basis of single negative values of these tests.
Provocative tests for coronary artery disease are not appropriate for patients with ongoing chest pain. In such patients, rest myocardial perfusion scans can be considered; a normal scan reduces the likelihood of coronary artery disease and can help avoid admission of low-risk patients to the hospital. Promising early results suggest that 64-slice CT and cardiac MRI may be of sufficient accuracy for diagnosis of coronary disease that these technologies may become widely used for patients with acute chest pain in whom the diagnosis is not clear. Clinicians frequently employ therapeutic trials with sublingual nitroglycerin or antacids or, in the stable patient seen in the office setting, a proton pump inhibitor. A common error is to assume that a response to any of these interventions clarifies the diagnosis. While such information is often helpful, the patient's response may be due to the placebo effect. Hence, myocardial ischemia should never be considered excluded solely because of a response to antacid therapy. Similarly, failure of nitroglycerin to relieve pain does not exclude the diagnosis of coronary disease. If the patient's history or examination is consistent with aortic dissection, imaging studies to evaluate the aorta must be pursued promptly because of the high risk of catastrophic complications with this condition. Appropriate tests include a chest CT scan with contrast, MRI, or transesophageal echocardiography.
Acute pulmonary embolism should be considered in patients with respiratory symptoms, pleuritic chest pain, hemoptysis, or a history of venous thromboembolism or coagulation abnormalities. Initial tests usually include CT angiography or a lung scan, which are sometimes combined with lower extremity venous ultrasound or D-dimer testing. If patients with acute chest discomfort show no evidence of life-threatening conditions, the clinician should then focus on serious chronic conditions with the potential to cause major complications, the most common of which is stable angina. Early use of exercise electrocardiography, stress echocardiography, or stress perfusion imaging for such patients, whether in the office or the emergency department, is now an accepted management strategy for low-risk patients. Exercise testing is not appropriate, however, for patients who (1) report pain that is believed to be ischemic occurring at rest or (2) have electrocardiographic changes 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 to benefit from acute treatment (Table 13-3). Pericarditis may be suggested by the history, physical examination, and ECG (Table 13-2). Clinicians should carefully assess blood pressure patterns and consider echocardiography in such patients to detect evidence of impending pericardial tamponade. Chest x-rays can be used to evaluate the possibility of pulmonary disease.
Guidelines and Critical Pathways for Acute Chest Discomfort Guidelines for the initial evaluation for patients with acute chest pain have been developed by the American College of Cardiology, American Heart Association, and other organizations. These guidelines recommend performance of an ECG for virtually all patients with chest pain who do not have an obvious noncardiac cause of their pain, and performance of a chest x-ray for patients with signs or symptoms consistent with congestive heart failure, valvular heart disease, pericardial disease, or aortic dissection or aneurysm. The American College of Cardiology/American Heart Association guidelines on exercise testing support its use in low-risk patients presenting to the emergency department, as well as in selected intermediate-risk patients. However, these guidelines emphasize that exercise tests should be performed only after patients have been screened for high-risk features or other indicators for hospital admission. Many medical centers have adopted critical pathways and other forms of guidelines to increase efficiency and to expedite the treatment of patients with high-risk acute ischemic heart disease syndromes. These guidelines emphasize the following strategies:
Rapid identification and treatment of patients for whom emergent reperfusion therapy, either via percutaneous coronary interventions or thrombolytic agents, is likely to lead to improved outcomes. Triage to non-coronary care unit monitored facilities such as intermediate-care units or chest pain units of patients with a low risk for complications, such as patients without new ischemic changes on their ECGs and without ongoing chest pain. Such patients can usually be safely observed in non- coronary care unit settings, undergo early exercise testing, or be discharged home. Risk stratification can be assisted through use of prospectively validated multivariate algorithms that have been published for acute ischemic heart disease and its complications. Shortening lengths of stay in the coronary care unit and hospital. Recommendations regarding the minimum length of stay in a monitored bed for a patient who has no further symptoms have decreased in recent years to 12 h or less if exercise testing or other risk stratification technologies are available. Nonacute Chest Discomfort The management of patients who do not require admission to the hospital or who no longer require inpatient observation should seek to identify the cause of the symptoms and the likelihood of major complications. Noninvasive tests for coronary disease serve both to diagnose this condition and to identify patients with
high-risk forms of coronary disease who may benefit from revascularization. Gastrointestinal causes of chest pain can be evaluated via endoscopy or radiology studies, or with trials of medical therapy. Emotional and psychiatric conditions warrant appropriate evaluation and treatment; randomized trial data indicate that cognitive therapy and group interventions lead to decreases in symptoms for such patients. Further Readings Brennan M-L et al: Prognostic value of myeloperoxidase in patients with chest pain. N Engl J Med 349:1595, 2003 [PMID: 14573731] Gibbons RJ et al: ACC/AHA 2002 guideline update for exercise testing. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing). Available at http://www.acc.org/qualityandscience/clinical/guidelines/exercise/dirindex.htm. Accessed on January 22, 2006 Gibson PB et al: Low event rate for stress-only perfusion imaging in patients evaluated for chest pain. J Am Coll Cardiol 39:999, 2002 [PMID: 11897442]
Heeschem C et al: Prognostic value of placental growth factor in patients with chest pain. JAMA 291:435, 2004 Kwong RY et al: Detecting acute coronary syndrome in the emergency department with cardiac magnetic resonance imaging. Circulation 197:531, 2003 Leber AW et al: Quantification of obstructive and nonobstructive coronary lesions of 64-slice computed tomography. J Am Coll Cardiol 46:147, 2005 [PMID: 15992649] Swap CJ, Nagurney JT: Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA 294:2623, 2005 [PMID: 16304077] Tong KL et al: Myocardial contrast echocardiography versus Thrombolysis in Myocardial Infarction score in patients presenting to the emergency department with chest pain and a nondiagnostic electrocardiogram. J Am Coll Cardiol 46:928, 2005 Tsai TT et al: Acute aortic syndromes. Circulation 205:3802, 2005