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GPAC: Guidelines and Protocols Advisory Committee Acute Chest Pain - Evaluation and Triage Effective Date: November 10, 2008 Summary | Flow Sheet | Patient Guide | Full Guideline in PDF Recommendations and Topics ScopeThe objective of this guideline is to improve the efficiency and effectiveness of diagnosing acute coronary syndrome (ACS) in patients with acute chest pain. Improved diagnostic testing will reduce the number of patients with ACS who go undiagnosed after initial evaluation. ACS includes unstable angina and acute myocardial infarction (ST segment elevation MI [STEMI] and non ST segment elevation MI [NSTEMI]). This guideline does not address chronic stable angina or the prevention of ACS. Target Population: Adults presenting with chest pain in physicians' offices, walk-in clinics and emergency departments. Applicable diagnostic codes: 410 (acute myocardial infarction); 411 (other acute and subacute forms of ischemic heart disease); 413 (angina pectoris). Evaluation and DiagnosisA. Selection of patients who may have ACS Patients presenting with prolonged (> 10 minutes) acute chest pain suggestive of ACS (see Appendix A for suggesting features) require a history and physical examination. If a patient presents in a physician's office or walk-in clinic and no alternative cause can be found with certainty, referral of the patient to the Emergency Department (ED) for further evaluation and observation is essential.1 If a previous electrocardiogram (ECG) is available, send it with the patient. Referral of a patient with suspected ACS to a laboratory for ECG and/or cardiac biomarkers*, rather than to the Emergency Department, is not appropriate. * The term cardiac biomarkers refers to proteins such as troponin I and T, myoglobin and creatinine kinase MB (CK-MB), which are released into the blood after heart muscle necrosis. Because of its greater sensitivity and superior tissue-specificity, cardiac troponin is the preferred biomarker for the detection of myocardial injury.2 B. Initial evaluation in the Emergency Department (ED) Patients with chest pain suggestive of ACS need further evaluation with a history, physical examination, ECG and cardiac biomarkers, preferably troponin (Appendix B). Consider other life threatening causes of chest pain, such as aortic aneurysm, pulmonary embolism, perforated viscus and pneumothorax. This guideline does not cover the diagnosis of these conditions. Criteria for acute myocardial infarction3 Detection of rise and/or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile (the upper reference limit) together with evidence of myocardial ischemia with at least one of the following:
C. Interpretation of troponin values It is recommended that emergency rooms have urgent troponin testing available.2 It is recommended that the laboratory reports the 99th percentile as the decision-limit for myocardial injury. If it is higher than the 99th percentile, use the level at which the coefficient of variation (CV) is 10 per cent for the specific assay in use in that laboratory.4 When an elevated troponin is detected, clinical context and serial sampling are needed to evaluate the result. A rising and/or falling level is indicative of a recent myocardial injury. In addition to acute myocardial infarction (AMI), low-level troponin elevations can occur in various other conditions, such as end-stage kidney disease and congestive heart failure.5 A stable troponin level in the equivocal range, i.e. less than the 99th percentile, is consistent with an ongoing chronic disorder directly or indirectly affecting the heart. It is not diagnostic of AMI. ManagementA. Management of patients with definite ACS
B. Management of patients with possible ACS
ST segment changes are often associated with causes other than those of ischemic origin. If there is uncertainty about the underlying cause of an abnormal ECG, consider obtaining an urgent consultation with a cardiologist or internist. There is currently insufficient evidence to recommend computed tomography (CT) angiography in the acute workup of a patient with possible ACS. RationaleAmong patients with chest pain, the diagnosis of acute coronary syndromes (ACS) may be missed because no single objective test reliably identifies ACS in these patients.7 Inappropriate discharge can lead to preventable acute myocardial infarction (AMI) or sudden death.8,9 A Canada-US study showed that 57-99% of patients presenting to an ED with chest pain were admitted for further investigation,10 and in the participating Canadian hospitals, only 13-51% of admitted patients ultimately proved to have an acute coronary syndrome. In a recent evaluation in two Vancouver hospitals, 4.5% of patients with an AMI and 6.8% of patients with unstable angina were discharged with a non-ACS diagnosis.9 The use of guidelines can help to improve these unacceptable high false negative rates. The need for a clinical decision tool is urgent and there is great potential for improvements in detecting ACS. Some US centres have established chest pain evaluation units (CPEUs) to limit unnecessary coronary care unit (CCU) admissions. These CPEUs apply 9-12 hour step-wise AMI rule-out protocols using observation, serial ECGs and cardiac biomarkers, provocative tests and cardiac imaging. The CPEUs have reported reduced costs and improvements in the identification of ACS compared with facilities that admit all patients to the CCU. Chest pain units are not widely established in British Columbia partly because their true cost-effectiveness is unknown. Clinical variables associated with ACS include gender, age, family history, previous angina or AMI, pain characteristics, syncope, response to nitro-glycerine, diaphoresis, nausea and vomiting, blood pressure, rales, jugular venous distension, added or unusual heart sounds, descriptive gestures and arrhythmias. Many of the above are strong predictors of ACS but their clinical utility in individual patients is uncertain.9 Women and patients with diabetes11 often do not complain of typical chest pain and may present with atypical symptoms. ECG abnormalities are strong positive predictors, but as many as 82% of patients have normal or near normal ECGs at initial presentation.12 Cardiac biomarkers including CK-MB, myoglobin and troponins are released during AMI. The sensitivity of CK-MB assays and troponins may not reach levels high enough at the initial assessment to rely on cardiac biomarkers alone to rule out AMI or unstable angina. Sensitivity improves with serial testing.13 Stress tests may be dangerous in high-risk patients, require skilled interpretation and have limited availability in small communities. Diagnostic uncertainty leaves physicians with the risk of discharging someone who has ACS or admitting someone who does not have ACS. The most difficult cases of ACS to identify are those with chest pain but negative ECGs and cardiac biomarkers. The American Heart Association (AHA) has recently published a revised guideline for the management of patients with unstable angina and non-ST elevation myocardial infarction (NSTEMI).1 The algorithm from the AHA guideline has been adapted (Appendix C) to help BC physicians diagnose and manage patients who present with chest pain in the ambulatory setting. A table of risk features is also provided (Appendix B) to aid in diagnosis. References
Resources (for health care providers and patients)Heart and Stroke Foundation of BC & Yukon St. Paul's Hospital Healthy Heart Program BCHealthGuide Online BCNurseLine American Heart Association American Academy of Family Physicians The Journal of the American Medical Association National Heart, Lung and Blood Institute National Institute for Health and Clinical Excellence (NICE) AppendicesAppendix A: Features of acute chest pain Appendix B: Risk of death or non-fatal MI in patients with Unstable Angina (UA)/NSTEMI Appendix C: Evaluation and management of patients suspected of having ACS SponsorsThis guideline was developed by the Guidelines and Protocols Advisory Committee, approved by the British Columbia Medical Association and adopted by the Medical Services Commission. This guideline is based on scientific evidence current as of the effective date. The principles of the Guidelines and Protocols Advisory Committee are to:
DisclaimerThe Clinical Practice Guidelines (the "Guidelines") have been developed by the Guidelines and Protocols Advisory Committee on behalf of the Medical Services Commission. The Guidelines are intended to give an understanding of a clinical problem, and outline one or more preferred approaches to the investigation and management of the problem. The Guidelines are not intended as a substitute for the advice or professional judgment of a health care professional, nor are they intended to be the only approach to the management of clinical problems. PDF Format Some documents on this Web site are in PDF format and require a PDF reader. If you do not have Adobe Acrobat Reader Version 7.0 or the most recent version of another PDF reader, you can download Adobe Acrobat Reader by clicking on the 'Get Adobe Reader' icon.
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