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Chest Pain in the Emergency Department: Uncertainty and the Test of Time

1991; Elsevier BV; Volume: 66; Issue: 9 Linguagem: Inglês

10.1016/s0025-6196(12)61586-9

1942-5546

Thomas H. Lee,

Cardiac Arrest and Resuscitation

When patients with acute chest pain are assessed in the emergency department, even the most experienced physicians become reacquainted with that sense of uncertainty that they first encountered as medical students. About 15% of these patients have acute myocardial infarction1Lee TH Goldman L The coronary care unit turns 25: historical trends and future directions.Ann Intern Med. 1988; 108: 887-894Crossref PubMed Scopus (83) Google Scholar and are therefore at increased risk for development of life-threatening complications. Determining which patients should be admitted to the hospital and the coronary-care unit, however, is difficult because no single piece of clinical data from the assessment in the emergency department can be relied on to diagnose or exclude ischemic heart disease.2Lee TH Cook EF Weisberg M Sargent RK Wilson C Goldman L Acute chest pain in the emergency room: identification and examination of low-risk patients.Arch Intern Med. 1985; 145: 65-69Crossref PubMed Scopus (377) Google Scholar The clinical and economic “stakes” in the physicians' triage decisions for these patients are high. When the diagnosis of acute myocardial infarction is overlooked and patients are sent home, the mortality during the next 72 hours is about 25%,3Lee TH Rouan GW Weisberg MC Brand DA Acampora D Stasiulewicz C Walshon J Terranova G Gottlieb L Goldstein-Wayne B Copen D Daley K Brandt AA Mellors J Jakubowski R Cook EF Goldman L Clinical characteristics and natural history of patients with acute myocardial infarction sent home from the emergency room.Am J Cardiol. 1987; 60: 219-224Abstract Full Text PDF PubMed Scopus (554) Google Scholar in comparison with about 6% for patients with infarction who are hospitalized.4White LD Lee TH Cook EF Weisberg MC Rouan GW Brand DA Goldman L Chest Pain Study Group Comparison of the natural history of new onset and exacerbated chronic ischemic heart disease.J Am Coll Cardiol. 1990; 16: 304-310Abstract Full Text PDF PubMed Scopus (36) Google Scholar Because of respect for this potentially catastrophic complication, physicians have a low threshold for admitting patients to the hospital; only about 3% of patients with infarction are dismissed from the emergency department.1Lee TH Goldman L The coronary care unit turns 25: historical trends and future directions.Ann Intern Med. 1988; 108: 887-894Crossref PubMed Scopus (83) Google Scholar Nonetheless, this excellent sensitivity for detecting infarction has been achieved only by the admission of many patients without infarction or other unstable conditions to the coronary-care unit and other monitored settings. Thus, about 70% of patients admitted to coronary-care units with suspected infarction ultimately have this diagnosis “ruled out.” Although some of these patients require monitoring for other problems, the in-hospital mortality for patients in whom acute infarction is excluded is only 0.3%.4White LD Lee TH Cook EF Weisberg MC Rouan GW Brand DA Goldman L Chest Pain Study Group Comparison of the natural history of new onset and exacerbated chronic ischemic heart disease.J Am Coll Cardiol. 1990; 16: 304-310Abstract Full Text PDF PubMed Scopus (36) Google Scholar In an era of increasingly constrained resources, the costs of admitting low-risk patients to monitored facilities cannot be ignored. My colleagues and I found that the mean (±SD) duration of stay for 274 patients admitted to Brigham and Women's Hospital for acute chest pain who did not have acute myocardial infarction or ischemic heart disease and who had no clinical complications was 2.7 ± 2.6 days, and their mean charges were $2,862 ± $2,292.5Udvarhelyi IS, Goldman L, Komaroff AL, Lee TH: Determinants of resource utilization for patients admitted for evaluation of acute chest pain. J Gen Intern Med (in press)Google Scholar Charges are not always an accurate reflection of the true costs of caring for patients, but the estimated costs of a day in the coronary-care unit at our institution exceed $1,200 (unpublished data)—a figure that does not include medications, tests, or professional fees. What help is available for the physician in the emergency department who is struggling with decisions about patients with chest pain? The best single test is electrocardiography. Although the initial electrocardiogram may be nondiagnostic in about 20% of patients with acute infarction, patients with infarction without electrocardiographic changes suggestive of ischemia have low rates of subsequent life-threatening complications6Rouan GW Lee TH Cook EF Brand DA Weisberg MC Goldman L Clinical characteristics and outcome of acute myocardial infarction in patients with initially normal or nonspecific electrocardiograms: a report from the Multicenter Chest Pain Study.Am J Cardiol. 1989; 64: 1087-1092Abstract Full Text PDF PubMed Scopus (235) Google Scholar, 7Brush Jr, JE Brand DA Acampora D Chalmer B Wackers FJ Use of the initial electrocardiogram to predict in-hospital complications of acute myocardial infarction.N Engl J Med. 1985; 312: 1137-1141Crossref PubMed Scopus (297) Google Scholar if they are admitted to the hospital. A normal or nonspecific electrocardiogram, however, does not indicate that patients can be safely dismissed from the emergency room to resume their usual activities. Other laboratory tests have proved disappointing. The development of rapid assays for creatine kinase and its MB isoenzyme8Lee TH Goldman L Serum enzyme assays in the diagnosis of acute myocardial infarction: recommendations based on a quantitative analysis.Ann Intern Med. 1986; 105: 221-233Crossref PubMed Scopus (237) Google Scholar has made these data available to the emergency department at many institutions, but the results of these assays are abnormal in only about a third of the patients with infarction at the time of initial assessment.9Lee TH Weisberg MC Cook EF Daley K Brand DA Goldman L Evaluation of creatine kinase and creatine kinase-MB for diagnosing myocardial infarction: clinical impact in the emergency room.Arch Intern Med. 1987; 147: 115-121Crossref PubMed Scopus (107) Google Scholar New radioimmunoassays for creatine kinase-MB,10Piran U Kohn DW Uretsky LS Bernier D Barlow EH Niswander CA Stastny M Immunochemiluminometric assay of creatine kinase MB with a monoclonal antibody to the MB isoenzyme.Clin Chem. 1987; 33: 1517-1520PubMed Google Scholar, 11Al-Sheikh W Heal VA Pefkaros KC Pina IL Serafini AN Ihmedian IH Ashkar FS Evaluation of an immunoradiometric assay specific for the CK-MB isoenzyme for detection of acute myocardial infarction.Am J Cardiol. 1984; 54: 269-273Abstract Full Text PDF PubMed Scopus (11) Google Scholar subforms of creatine kinase-MB,12Puleo PR Guadagno PA Roberts R Scheel MV Marian AJ Churchill D Perryman MB Early diagnosis of acute myocardial infarction based on assay for subforms of creatine kinase-MB.Circulation. 1990; 82: 759-764Crossref PubMed Scopus (126) Google Scholar and creatine kinase isoforms13Hashimoto H Abendschein DR Strauss AW Sobel BE Early detection of myocardial infarction in conscious dogs by analysis of plasma MM creatine kinase isoforms.Circulation. 1985; 71: 363-369Crossref PubMed Scopus (36) Google Scholar, 14Jaffe AS Serota H Grace A Sobel BE Diagnostic changes in plasma creatine kinase isoforms early after the onset of acute myocardial infarction.Circulation. 1986; 74: 105-109Crossref PubMed Scopus (56) Google Scholar have been developed; thus, more rapid and specific diagnosis of acute myocardial infarction may be possible in the future. It seems unlikely, however, that these tests will have sufficient sensitivity for detecting infarction that a normal result will justify a decision to dismiss a patient. Poor sensitivity also limits the usefulness of other tests that have been studied in the emergency department, including determination of serum myoglobin15Gibler WB Gibler CD Weinshenker E Abbottsmith C Hedges JR Barsan WG Sperling M Chen I-W Embry S Kereiakes D Myoglobin as an early indicator of acute myocardial infarction.Ann Emerg Med. 1987; 16: 851-856Abstract Full Text PDF PubMed Scopus (104) Google Scholar and two-dimensional echocardiography.16Oh JK Miller FA Shub C Reeder GS Tajik AJ Evaluation of acute chest pain syndromes by two-dimensional echocardiography: its potential application in the selection of patients for acute reperfusion therapy.Mayo Clin Proc. 1987; 62: 59-66Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar Therefore, the finding by Gay and associates, in a study reported in this issue of the Proceedings (pages 885 to 891), that lipoprotein analysis is of no value in the assessment of chest pain in the emergency department should not be surprising. An increased cholesterol level is a risk factor for the development of coronary disease, and Goldman and co-workers17Goldman L Cook EF Mitchell N Flatley M Sherman H Rosati R Harrell F Lee K Cohn PF Incremental value of the exercise test for diagnosing the presence or absence of coronary artery disease.Circulation. 1982; 66: 945-953Crossref PubMed Scopus (59) Google Scholar have previously shown that it is a significant independent correlate of the presence of coronary artery disease. As demonstrated in the current report, however, this correlation is too weak to be of value in the assessment of patients with suspected myocardial infarction or acute ischemic heart disease. The multivariate analysis demonstrates that the electrocardiogram and the “clinical impression”—which integrates several pieces of clinical data—were the independent correlates of the final diagnosis. Gay and colleagues have performed a service by substantiating the lack of usefulness of lipoprotein analyses in the assessment of this patient population because clinicians may be subtly swayed by these data when they are available. In the course of our investigations of this syndrome, my colleagues and I have reviewed many thousands of emergency department records, some of which reflected a low or normal cholesterol level as part of the justification for decisions to send patients home. This report clearly indicates that lipoprotein analyses should not play a role in this decision-making process. Instead, the physician should rely on data from the history, physical examination, and electrocardiogram. To help clinicians integrate these data, we and others have developed multivariate algorithms for the identification of patients with acute myocardial infarction18Goldman L Cook EF Brand DA Lee TH Rouan GW Weisberg MC Acampora D Stasiulewicz C Walshon J Terranova G Gottlieb L Kobernick M Goldstein-Wayne B Copen D Daley K Brandt AA Jones D Mellors J Jakubowski R A computer protocol to predict myocardial infarction in emergency department patients with chest pain.N Engl J Med. 1988; 318: 797-803Crossref PubMed Scopus (524) Google Scholar and acute ischemic heart disease.19Pozen MW D'Agostino RB Selker HP Sytkowski PA Hood Jr, WB A predictive instrument to improve coronary-care-unit admission practices in acute ischemic heart disease: a prospective multicenter clinical trial.N Engl J Med. 1984; 310: 1273-1278Crossref PubMed Scopus (479) Google Scholar These decision aids are intended to assist the risk-stratification process by providing physicians access to experience based on thousands of patients. It is hoped that improved identification of patients who are at low risk for major complications will allow physicians to triage them to lower levels of care or perhaps dismiss them from the emergency department. Pozen and associates19Pozen MW D'Agostino RB Selker HP Sytkowski PA Hood Jr, WB A predictive instrument to improve coronary-care-unit admission practices in acute ischemic heart disease: a prospective multicenter clinical trial.N Engl J Med. 1984; 310: 1273-1278Crossref PubMed Scopus (479) Google Scholar performed a study in which physicians who were assessing patients with chest pain in the emergency department were given predictions of the patients' risks of acute ischemic heart disease by a study nurse. This intervention led to decreased rates of admission of patients with this diagnosis to the hospital and coronary-care unit; however, whether the influence of this intervention resulted from the information per se or from the human interaction needed to transmit it is uncertain. Furthermore, physicians in other settings have been reluctant to use this decision aid when it was not provided by human beings.20Corey GA Merenstein JH Applying the acute ischemic heart disease predictive instrument.J Fam Pract. 1987; 25: 127-132PubMed Google Scholar Thus, the current “state of the art” for such decision aids is that they seem to be valid predictors of risks, but the optimal method of integrating their use has not been identified and their ability to improve efficiency remains uncertain. Perhaps the only test that can eliminate uncertainty completely for patients with suspected myocardial infarction is time itself—a period of observation during which serial electrocardiograms and determinations of cardiac enzymes are obtained. The usual “rule out myocardial infarction” admission has been 24 hours, but we have recently shown that a 12-hour observation period is appropriate for patients with a low risk of infarction in the emergency department, as assessed with a previously validated decision aid.21Lee TH Juarez G Cook EF Weisberg MC Rouan GW Brand DA Goldman L Ruling out acute myocardial infarction: a prospective multicenter validation of a 12-hour strategy for patients at low risk.N Engl J Med. 1991; 324: 1239-1246Crossref PubMed Scopus (235) Google Scholar These findings should not be interpreted as a recommendation that patients be dismissed after 12 hours, but further diagnostic evaluations such as exercise testing and transfer to lower levels of care can be considered at that point. It seems unlikely that any test other than the test of time will ever completely remove uncertainty from the assessment of patients with acute chest pain in the emergency department. Even if uncertainty will always exist, physicians and institutions can minimize the anxiety associated with the triage of these patients by developing strategies for their care. The use of decision aids such as multivariate algorithms that can refine the risk-stratification process is one approach. Another is the development of low-cost alternatives to the coronary-care unit for patients whose risk for infarction is not sufficiently low that dismissal to home seems appropriate. One approach is initial triage to an intermediate-care or step-down unit, which is a cost-effective alternative to the coronary-care unit for patients with a risk of myocardial infarction of 5 to 20%.22Fineberg HV Scadden D Goldman L Care of patients with a low probability of acute myocardial infarction: cost effectiveness of alternatives to coronary-care-unit admission.N Engl J Med. 1984; 310: 1301-1307Crossref PubMed Scopus (213) Google Scholar These facilities, which include central electrocardiographic monitoring but have a lower nurse-to-patient ratio than coronary-care units, have expanded at many institutions in recent years. In the past, they were used as the next level of care for patients leaving the coronary-care or intensive-care unit (thus the name “step-down unit”). Currently, however, they are being used as the initial level of care for many patients with acute myocardial infarction, and observational data suggest that patients with relatively low probabilities of acute myocardial infarction have similar outcomes with intermediate and intensive care.23Fiebach NH Cook EF Lee TH Brand DA Rouan GW Weisberg M Goldman L Outcomes in patients with myocardial infarction who are initially admitted to stepdown units: data from the Multicenter Chest Pain Study.Am J Med. 1990; 89: 15-20Abstract Full Text PDF PubMed Scopus (54) Google Scholar My colleagues and I recently described our clinical experience with a new short-stay coronary observation unit,24Gaspoz JM, Lee TH, Cook EF, Weisberg MC, Goldman L: Outcomes of rule-out myocardial infarction patients admitted to a new short stay unit. Am J Cardiol (in press)Google Scholar a two-bed non-intensive-care unit with telemetry monitoring adjacent to the emergency department. This unit is used for patients with a low risk of acute myocardial infarction who do not have cardiac or noncardiac problems that necessitate more than minimal nursing care. Among the first 512 patients admitted to this unit, the rate of acute myocardial infarction was 3%, and only one serious complication occurred while patients were in the unit. The median duration of stay was 1 day. Fewer than half of the patients with chest pain in the emergency department are dismissed home,1Lee TH Goldman L The coronary care unit turns 25: historical trends and future directions.Ann Intern Med. 1988; 108: 887-894Crossref PubMed Scopus (83) Google Scholar and it seems unlikely that lipoprotein analysis or any test can substantially increase that rate without subjecting patients to inappropriate risks. Therefore, efforts to reduce health-care costs without harming patients may have to focus on rapid and repeated stratification of risks for patients after admission to the hospital and development of low-cost facilities such as the coronary observation unit.