Triage of Patients with Acute Chest Pain and Possible Cardiac Ischemia: The Elusive Search for Diagnostic Perfection

Quality Grand Rounds is a series of articles and companion conferences designed to explore a range of quality issues and medical errors. Presenting actual cases drawn from institutions around the United States, the articles integrate traditional medical case histories with results of root-cause analyses and, where appropriate, anonymous interviews with the involved patients, physicians, nurses, and risk managers. Cases do not come from the discussants' home institutions. Summary of the Case Mrs. T., a 68-year-old woman with many cardiac risk factors and a history of myocardial infarction (MI), presented with atypical symptoms but a changed electrocardiogram (ECG). These ECG changes were not appreciated by Dr. M., the emergency department physician, and Mrs. T. was mistakenly sent home with what proved to be an acute MI. Dr. M. was interviewed by a Quality Grand Rounds editor on 21 March 2002. The Case Twelve hours before presenting to the emergency department, Mrs. T. called the hospital's telephone triage nurse and reported dull, midsternal pain relieved after a bowel movement. After probing for associated symptoms, the nurse reassured the patient and told her to call back if she experienced any further discomfort. Several hours later, when the pain recurred, Mrs. T. called again. When asked whether she had sublingual nitroglycerin on hand, Mrs. T. confirmed that she had a bottle of nitroglycerin pills but that the expiration date had passed. She was told to take the nitroglycerin if the pain recurred and was given an appointment for 2 days later (at which time she was instructed to exchange her expired bottle for a new one). She was advised to call 911 if the pain recurred and was associated with nausea, diaphoresis, or dyspnea. Because of continued pain, the patient came into the emergency department of a large urban hospital 4 hours later (at approximately 2:00 a.m.) with a chief symptom of chest pain. The patient had a history of inferior-wall MI, hypertension, diabetes mellitus, hyperlipidemia, and peripheral vascular disease. She described the pain as very different from any pain that she had experienced in the past. It had a burning quality, was located across her epigastrium and chest, persisted for 4 to 6 minutes at a time, and had been intermittent for 24 hours. The pain came on at rest and was relieved by activity. She reported no associated dyspnea, diaphoresis, or nausea. Review of systems revealed 1 week of constipation. Dr. M., a moonlighting internist, was awakened from sleep to evaluate the patient. Physical examination revealed a pulse of 85 beats/min, blood pressure of 140/70 mm Hg, and respiratory rate of 18 breaths/min. The lungs were clear to auscultation, and heart sounds were normal, with no rubs, murmurs, or gallops. The ECG (obtained during a painful episode) was interpreted as sinus rhythm, with normal axis and normal intervals ( Figure 1 , top). Dr. M. noted a Q wave in lead III but specifically noted the absence of ST-segment and T-wave changes consistent with ischemia. The patient was discharged from the emergency department 1 hour later with a diagnosis of chest and abdominal pain secondary to constipation. She was prescribed a regimen to relieve constipation and was told to schedule a follow-up appointment with her primary physician. Figure 1. Electrocardiograms ( ECGs ) obtained at presentation and a previous comparison tracing. Top. Bottom. Diagnosing Chest Pain in the Emergency Department Few diagnostic decisions have been more heavily researched than the approach to the patient with acute chest pain. In the context of the patient safety movement, it is useful to consider this case not only for what it teaches us about triaging patients with acute chest pain but also for what it may reveal about improving the individual physician's diagnostic performance through the use of algorithms or protocols. Chest pain accounts for about 5.6 million emergency department visits annually, second only to abdominal pain as the most common reason for an emergency department visit. Approximately 1% to 4% of patients who present to an emergency department with what is actually an acute MI are mistakenly discharged (1-8), and the percentage of missed diagnoses increases when the denominator includes not only acute MI but also unstable angina. Patients discharged from the emergency department with MI have a generally worse prognosis than do appropriately hospitalized patients with MI (1-4), partly because of their risk for sudden death but also because of the delay in implementing treatments that are known to be effective for MI or the acute coronary syndrome (unstable angina or nonST-elevation MI). Patients with atypical symptoms, and especially patients without chest pain (2, 3), are most likely to be mistakenly discharged. The clinical question is which patients with acute chest pain have a presentation benign enough to make discharge from the emergency department safe and appropriate. Cost-effectiveness analyses suggest that a coronary care unit is the appropriate triage option for patients whose probability of acute MI is about 20% or higher (9, 10). For patients whose risks for MI or acute coronary ischemia are lower (5-8, 11), admission to telemetry units is often recommended, including a short stay on a chest pain (or coronary) evaluation or observation unit. In analyzing Mrs. T.'s presentation, it is essential to determine whether any combination of initial symptoms, signs, laboratory studies, or ECG findings has enough discriminatory power to reduce the likelihood of misdiagnosing an acute coronary syndrome to a level that would render discharge from the emergency department safe and appropriate. In the acute setting, the ECG is not only the most important piece of information (12), it is nearly as important as all other information combined. About 80% of patients with acute MI have an initial ECG that shows evidence of infarction or ischemia not known to be old (Figure 2), and any patient who has such abnormalities has too high a risk to be safely discharged, regardless of the clinical history or physical examination (13, 14). The sensitivity is lower if the goal is to identify ischemia in addition to infarction, but comparisons with previous ECGs can improve the accuracy and usefulness of interpreting the ECG (15). Although a normal ECG at presentation predicts a relatively lower risk for complications (16-18), it cannot absolutely exclude myocardial ischemia or even MI. For example, among patients mistakenly discharged from the emergency department, up to 50% have normal or nondiagnostic ECG findings (2, 19). Thus, even if Mrs. T.'s ECG had been normal or unchanged from her previous ECG, this would not have had enough negative predictive value to exclude an acute MI or the acute coronary syndrome. Figure 2. Receiver-operating characteristic curve of the initial electrocardiographic interpretation. MI New The description of the presenting symptom is also important. Patients with chest pain are more likely to have MI or the acute coronary syndrome (7, 8, 11, 14), but up to 25% of patients with these diagnoses may present with symptoms such as shortness of breath, dizziness, or weakness, so cardiac ischemia must also be considered in patients with these symptoms. Demographic factors and traditional cardiovascular risk factors (with the very notable exception of a history of MI or coronary disease [5, 6, 20, 21]) are of little importance in predicting the cause of acute chest pain (21-24). Aspects of the medical history that appreciably lower the patient's likelihood of ischemia (likelihood ratios of approximately 0.2) include reproducibility of pain with palpation or positional changes, pleuritic pain, stabbing pain, or pain radiating to the lower extremities (5, 6, 20, 21, 24). However, even these negative predictors cannot reliably exclude MI (20, 25). Mrs. T.'s description of painful episodes lasting only 4 to 6 minutes may also seem atypical, but the duration of symptoms is not a useful predictor (5, 7-9) unless the pain has persisted for 48 hours or more without ECG changes (5, 6). Patients who describe their pain as similar to previous episodes of cardiac ischemia are in a high-risk category (5, 18), but any chest pain carries a higher risk than no pain (7, 8, 11). Although the precise reproduction of chest pain by local palpation decreases risk (5, 18), normal results on physical examination do not lower the risk (5, 18, 20, 24). How can these data have been used in caring for Mrs. T.? She had pain that was different from her previous MI and was thought to have an unchanged ECG. If it is assumed that all of these data are accurate, she would have had less than a 7% risk for MI and a low risk for complications that would require intensive care (18). However, because of her history of coronary disease and the absence of a clear-cut benign diagnosis, because constipation is not an established cause of chest pain, and because her pain had not resolved, she is the type of patient for whom admission to a chest pain evaluation unit is appropriate (20, 21, 26-33) (Table). It is very important for individual hospitals to adopt clear guidelines for triaging such patients, because these patients may be evaluated by many different physicians with varying experience, knowledge, personality traits, and levels of fatigue (8, 34, 35). Table. Recommended Strategies for Determining Where To Admit Patients with Acute Chest Pain for Treatment of Ongoing Life-Threatening Conditions* Dr. M.: I think one of the factors that affected my decision making when I first evaluated the patient was the time of night (2:00 a.m.) and the fact that I had just awakened. I saw her less than a minute after being awakened. What I probably should have done was had her stay in the emergency department, even if I thought she was low risk (which I obviously at that time did), and let more time pass so that my sleep ine