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Short-term risk after initial observation for chest pain
The Journal of Emergency Medicine, Vol. 25, No. 4, pp. 357⫺362, 2003 Copyright © 2003 Elsevier Inc. Printed in the USA. All rights reserved 0736-4679/03 $–see front matter
doi:10.1016/S0736-4679(03)00238-5
Original Contributions
SHORT-TERM RISK AFTER INITIAL OBSERVATION FOR CHEST PAIN Christopher Lai,
MD,*
Thomas P. Noeller,
MD,*
Kristen Schmidt, Emerman, MD*
MD,*
Peter King,
MD,†
and Charles L.
*Department of Emergency Medicine, Cleveland Clinic Foundation, Cleveland, Ohio, and †Department of Emergency Medicine, Ohio Permanente Medical Group, Cleveland, Ohio Reprint Address: Charles L. Emerman, MD, Department of Emergency Medicine, Cleveland Clinic Foundation, 9500 Euclid Avenue/E19, Cleveland, OH 44195
e Abstract—Few studies have evaluated the necessity of immediate stress testing after observation for chest pain. The purpose of this study was to assess the safety of outpatient stress testing after discharge from a chest pain unit. We hypothesized that discharge from a chest pain unit before stress testing is associated with a low rate of shortterm adverse outcomes. This was a retrospective chart review of managed care patients discharged from the chest pain unit before the performance of stress testing. Records were reviewed for the occurrence of adverse cardiac outcomes before an outpatient stress test up to 60 days postdischarge. Primary outcomes were defined as death or myocardial infarction, and secondary outcomes as readmission for chest pain evaluation, unstable angina, or congestive heart failure. Three hundred forty-four patients were identified. One hundred sixty-six patients had either a recent prior stress test (17) or an outpatient test (149) performed within 60 days of discharge. During that time, 2 patients (0.6%) had a fatal out-of-hospital cardiac event, and there were 27 subsequent chest pain visits to the Emergency Department by 24 patients (7.0%). Nine patients (2.6%) were admitted to the hospital and 10 (2.9%) were readmitted to the observation unit for chest pain. We conclude that patients who have negative serial electrocardiograms and enzyme testing in a chest pain unit are at low risk for shortterm cardiac events. Appropriately selected patients may be discharged for subsequent outpatient testing. © 2003 Elsevier Inc.
INTRODUCTION Chest pain accounts for 5– 6 million visits to Emergency Departments (EDs) across the country every year and can be associated with coronary artery disease, the leading cause of death in the United States (1,2). Approximately 2% of patients with acute coronary syndromes are mistakenly discharged from the ED (3). With the additional benefit of a chest pain observation unit, the ED can decrease the number of missed myocardial infarctions without utilizing scarce hospital resources for low risk patients (4 – 6). Although there are differences in chest pain protocols, observation units generally follow a strategy to identify myocardial infarction (MI), unstable angina, and exercise-induced ischemia. After an MI has been ruled out by serial cardiac marker measurements and electrocardiography (EKG), a stress test may be done to evaluate cardiac risk and determine the need for further intervention. A negative stress test indicates a low risk of shortterm adverse cardiac events, whereas a positive result indicates higher risk and the need for more aggressive intervention (7–9). Providing stress tests every day of the week requires substantial resources. Because short-term risk after discharge from a chest pain unit without a stress test has not been well defined, it is not clear whether that commitment of resources is necessary. The purpose of this study
e Keywords— chest pain; observation; emergency service; hospital; exercise test; myocardial infarction
RECEIVED: 1 May 2002; FINAL ACCEPTED: 8 April 2003
SUBMISSION RECEIVED:
28 February 2003; 357
358
C. Lai et al.
was to evaluate the short-term safety of discharging observation unit patients after serial markers and EKGs with referral for further outpatient assessment and stress testing.
MATERIALS AND METHODS This was a retrospective chart review of patients admitted to our observation unit for chest pain evaluation on a Friday or Saturday from January 1998 to December 2000. Because these patients were discharged on the weekends when no stress testing was immediately available, they were routinely referred to their primary care provider (PCP) for follow-up evaluation and stress testing. Patients were identified by a search of the observation unit admission and discharge logs for diagnoses of chest pain, unstable angina, and “rule-out MI.” We limited our search to patient members of one managed care plan (Kaiser Permanente) with the expectation that complete follow-up data would be available. Patients were included only if they had information available in the managed care plan or hospital records to determine their 60-day outcome. Data were abstracted by a single reviewer using a standardized data collection form. The Cuyahoga County Coroner’s records were reviewed for any patients in whom 60-day outcome could not be determined from the managed care database or hospital records. Patients were excluded if they were admitted to the hospital from the observation unit for any reason at the index visit or if they had a stress test during this index visit. For patients with multiple ED visits, only the first one was considered. In the observation unit, patients underwent serial EKG and cardiac enzyme testing every 4 h for a total of 12 h while on continuous cardiac monitoring. The EKGs were over-read at the time by a cardiologist and subsequently categorized by one of the investigators who was blinded to the clinical data. Our experience is that 1% to 2% of patients will “rule-in” during observation unit evaluation. Patients who were felt to be high risk by the treating physician were admitted if it was felt to be unsafe to discharge the patient before stress testing. Patients who were discharged on the weekends were scheduled for outpatient testing at the discretion of the treating physician. The patients’ prior and subsequent cardiac evaluation, including stress tests or catheterization, were reviewed and categorized. The primary outcome was defined as death or MI within 60 days of discharge or before outpatient stress testing. Secondary outcomes included repeat visits resulting in hospital or CDU admission for chest pain, unstable angina, or congestive heart failure. Events that
Table 1. Study Demographics Descriptor
Cardiac event (%)
No cardiac event (%) p value
Age (years) 57.9 ⫾ 13.6 Gender Male 44.8 Race Caucasian 23.9 Risk factors Prior CAD 26.6 Prior MI 13.4 Prior revascularization 12.5 Hypertension 100 Diabetes 24.8 Hyperlipidemia 32.8 Cigarette use 24.2
60.3 ⫾ 13.3
⬍ 0.05
44.4
ns
33.3
ns
66.7 11.1 11.1 66.8 33.3 33.3 11.1
⬍ 0.05 ns ns ns ns ns ns
CAD ⫽ coronary artery disease; MI ⫽ myocardial infarction.
occurred during the index visit were not included. Stress test results were based on cardiology or radiology staff interpretations as documented in the medical record. An abnormal stress test was defined by the presence of findings indicating stress-induced ischemia. Follow-up data were obtained from review of the managed care organization and hospital records. Data were reviewed for patient demographics, details of the chest pain evaluation, 60-day outcomes, and stress testing. Descriptive data are presented as means and standard deviations, or as proportions. Fisher’s exact test or Students t-test was used as appropriate, and a p value less than 0.05 was considered statistically significant. This study was approved by the IRB of both the hospital and the managed care organization, and was in accordance with the Declaration of Helsinki. RESULTS Four hundred and forty-two patients were identified, of whom 98 were excluded for the following reasons. Thirty-one of the excluded patients were kept beyond 24 h and underwent stress testing the next day, 30 patients were admitted to the hospital, 19 visits were duplicate entries or repeat visits, 8 patients were misidentified in the log and were not observed for cardiac evaluation, 5 patients had an insurance change and were not in the Kaiser system, and 5 patients were otherwise lost to follow-up. Three hundred forty-four patients met study criteria. Patients were 19 to 95 years of age (mean 59.6, SD 13.7) (Table 1). One hundred fifty-four (44.8%) patients were male. Approximately 73.8% of the patients were African American, 24.1% were white, and 2.1% were listed as other. The most frequently documented cardiac risk fac-
Short-term Risk After Chest Pain
359
Table 2. Outcome of Observation Unit Care Category Observation Unit Discharge Dx
Follow-up Follow-up study
Results
Subject
Number
%
Non-cardiac chest pain Reflux Musculoskeletal Angina Unstable angina Other Number with PCP Average days after ED visit # with repeat ED visits Exercise stress Stress thallium Stress echocardiography Catheterization Normal Abnormal Indeterminate
248 35 34 5 1 21 190 9 24 85 50 10 4 103 24 22
72.1 10.2 9.9 1.5 0.3 6.1 55.2 7.0 24.7 14.5 2.9 1.2 69.1 16.1 14.8
tor was hypertension (67.7%), followed by hypercholesterolemia (32.8%) and known coronary artery disease (CAD) or angina (27.6%). Two hundred forty-nine patients (72.4%) did not have a prior history of CAD. Forty-three patients (12.5%) had a previous coronary artery bypass graft (CABG) or stent placement and 46 patients (13.4%) had a previous MI. The most common chief complaint was chest pain (86.9%). The majority of EKGs were categorized as non-specific ST-T wave changes (41.9%), followed by normal (36.9%) and old infarction (5.8%). The most common chest pain observation unit discharge diagnosis was noncardiac chest pain (72.1%) followed by gastroesophageal reflux (10.2%) and musculoskeletal pain (9.9%) (Table 2). In follow-up, 190 patients (55.2%) visited their PCP within an average of 9 (range 2–38) days after the index visit. One hundred forty-nine patients (43.3%) had a
Figure 1. Results of follow-up stress testing.
stress test. In total, 295 patients (85.8%) followed up with their PCP or had a stress test. The stress tests were performed an average of 22 ⫾ 15 days after the ED visit. The most frequent type of evaluation was exercise stress testing, followed by stress thallium, stress echocardiography, and catheterization (Table 2). The results are displayed in Figure 1. One hundred sixty patients (46.5%) had records of a prior cardiac evaluation (Figure 2). One hundred nine of these tests (31.7%) were normal, 35 (10.2%) were abnormal, 15 (4.4%) were indeterminate, and the result of 1 study (0.3%) was unknown. Only 34.3% of patients with a prior stress test had another stress test performed within the follow-up period compared with 51.1% of patients with no prior stress test (p ⫽ 0.002). Those with a history of an exercise treadmill test were most likely to have a study in follow-up (43.9%) compared with the least likely group, those who had a prior nuclear imaging test (18.2%; p ⫽ 0.008). Of the 195 patients who did not have an outpatient stress test, the emergency physician determined that 18 patients (5.2%) did not require one, and the PCP or cardiologist determined 79 patients (23.0%) did not require one. Nineteen patients (5.5%) refused a stress test. Seventeen patients (4.9%) had a recent stress test and 13 patients (3.8%) had a stress test scheduled after the 60-day period. Forty-nine patients (14.2%) did not follow up with their PCP. In follow-up, there were 27 return visits by 24 patients (7.0%) to the ED for chest pain. After the second visit, 5 patients were discharged home, 10 were admitted to the CDU, and 9 were admitted to the hospital (Table 3). None of these patients had a myocardial infarction. Eight patients had cardiac evaluation during this admission. Four had normal results, three had abnormal results, and one was indeterminate. Two patients died during the follow-up period as a
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Figure 2. Patients with prior cardiac evaluations.
result of out-of-hospital cardiac arrest. One of these arrests occurred 4 days after discharge, whereas the other occurred 49 days after discharge after several outpatient and ED evaluations. The primary outcome of death or MI was, therefore, documented in 2 (0.6%; 95% CI 0.1–2.1%) of the patients and the secondary outcome occurred in 19 (5.5%, 95% CI 3.4 – 8.5%) patients.
DISCUSSION We found that patients monitored in a chest pain observation unit have a low likelihood of significant cardiac events up to 60 days after discharge. This finding is consistent with other reports that patients evaluated with serial cardiac markers are at low risk for early adverse outcomes (5,10,11). Most previous studies have evaluated the short-term risk after observation unit-based stress testing. Patients discharged after a negative stress test have a low likelihood of subsequent cardiac events and few repeat ED
Table 3. Outcomes
Primary Death MI Secondary (Revisits) Discharged CDU Admitted CHF UA CP
#
%
95% CI
2 0
0.6 0
0.1–2.1 0.0–1.1
5 10 9 1 4 4
1.5 2.9 2.6 0.3 1.2 1.2
0.5–3.4 1.4–5.3 1.2–4.9 0.1–1.6 0.3–3.0 0.3–3.0
MI ⫽ myocardial infarction; CDU ⫽ ; CHF ⫽ congestive heart failure; UA ⫽ ; CP ⫽ .
visits and admissions (12–15). Even in patients who have had previous cardiac complications such as MI, angioplasty, or stent placement, a negative stress test implies a benign short-term course (16 –18). Mikhail et al. performed stress tests on 424 patients initially evaluated in their observation unit. None of the 400 (94%) patients with a negative stress test had a cardiac event within 14 days (8). Kirk et al. followed patients with a negative or non-diagnostic exercise stress test for 30 days and documented no cardiac events. Moreover, patients with a positive stress test had no documented cardiac mortality, although 10.7% of these patients returned to the ED within 30 days (19). Polanczyk et al. found a 17% re-visit rate among patients with a negative stress test, compared with 7% of our patients with no stress test. In their study, 2% of those with a negative exercise stress test experienced a cardiac event within 6 months, including MI, coronary artery bypass graft, and angioplasty (13). Diercks et al. reported a 1-year cardiac complication rate of 1.1% (including coronary artery bypass graft, percutaneous transluminal angioplasty, cardiogenic shock, ventricular fibrillation/tachycardia arrest, and myocardial infarction) for patients with a negative exercise stress test, compared with 36.8% in those with a positive test (20). Although the rate of death or MI in our study may be as high as 2.1%, the safety of discharging patients from the CDU without immediate stress testing seems comparable to an approach that includes immediate stress testing. It is unknown whether an immediate stress test would have prevented the two fatal events. It can be theorized that immediate stress testing might decrease the rate of return visits for chest pain or decrease the rate of admission for those returning, but further study is needed in this area. The potential benefits of discharging patients without immediate stress testing are somewhat institution-spe-
Short-term Risk After Chest Pain
cific. Availability of stress tests based on hospital resources and stress laboratory schedules will dictate how many tests are available for ED patients each day. Length-of-stay in the observation unit would be decreased if the patient is discharged once the “rule-out” protocol is completed without the need to wait for a stress test. Stress testing is just one tool used by clinicians for risk-stratification in a chest pain unit. In addition to a careful history that includes screening for traditional risk factors, consideration might be given to measurement of total cholesterol if not documented by the patient’s PCP. This is an opportunity to take advantage of a “teachable moment.” If the total cholesterol, HDL, LDL, or triglycerides are abnormal, patients are at higher risk for adverse outcomes and can be appropriately counseled and referred. Serum markers of inflammation such as C-reactive protein (CRP) have recently been incorporated as riskstratification tools in some, particularly high-risk, patient populations (21). Inflammation is increasingly recognized as a significant phenomenon in acute coronary syndromes. There are, as yet, no clear guidelines on the acute management of CDU patients with an elevated CRP compared to those with a normal CRP. However, it is clear that those with abnormal elevations are at higher risk for adverse outcomes and may be candidates for more aggressive interventions and certainly close followup, including risk factor modification. Elevated B-type natriuretic peptide (BNP), commonly measured now in patients with congestive heart failure, has been associated with a worse prognosis in patients with acute coronary syndromes (22,23). A “multimarker” approach incorporating troponin, CRP, and BNP recently has been shown to stratify risk for both short- and long-term outcomes in patients with ACS (24). The focus of the emergency physician is on the detection of an acute coronary event, but patients in a chest pain unit are excellent candidates for risk factor assessment that may help with acute decisions as well as with appropriate referral and risk-factor modification. The availability of follow-up is a critical issue in determining the safety of delayed stress testing. This study examined a managed care population, all of whom had an assigned PCP. About 86% of patients in our study received follow-up by 60 days, either with a stress test or by a visit to their doctor. Whether this would occur in another environment is unknown. In fact, having a primary physician is the most important factor in determining the likelihood that a patient will follow up (25). Lack of insurance and worries about cost have been cited as barriers to follow-up in other settings (26). Prior studies have evaluated other strategies to enhance follow-up,
361
including contact with the PCP and direct scheduling of outpatient appointments (27). Our study is limited by the small number of patients and the retrospective nature of this review. Confidence intervals around adverse event rates would be tighter if a larger group of patients was included. However, the overall event rate is consistent with that found in other studies evaluating chest pain unit follow-up. A formal risk-stratification scheme was not used to determine suitability for discharge. Rather, the decision to admit or discharge for outpatient follow-up was left to the discretion of the attending physician. Utilization of a riskstratification score to help determine suitability for immediate vs. outpatient stress testing is a focus of current research. The study population was derived from a single center caring for members of a managed care plan, which may have a different spectrum of cardiac disease than other ED populations. The managed care plan used in this study, however, enrolls a broad spectrum of patients. The age and ethnicity of the study sample, for example, is typical of an urban population seen in many EDs. Because these patients have primary care providers, it can be reasoned that they are more likely to follow up than others such as the uninsured. The safety of discharging patients from a CDU without stress testing is likely to be realized only in a group of patients who are likely to follow up.
CONCLUSION Patients discharged from a chest pain observation unit after appropriate evaluation, including serial electrocardiography and serum cardiac marker measurements, are at low short-term risk for adverse cardiac outcomes. Appropriately selected patients may be discharged for early follow-up and outpatient evaluation.
REFERENCES 1. National Center for Health Statistics. National Hospital Ambulatory Medical Care Survey; 1999. Emergency Department Summary. NCHS web page: www.cdc.gov/nchs/data/ad/ad320.pdf. 2. American Heart Association. 2001 heart and stroke statistical update. Dallas, TX: American Heart Association; 2000. 3. Pope JH, Azufderheide TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med 2000;342:1163–70. 4. Lee TH, Juarez G, Cook EF, et al. A prospective multicenter validation of a 12-hour strategy for patients at low risk. N Engl J Med 1991;324:1239 – 46. 5. Gaspoz JM, Lee TH, Weinstein MC, et al. Cost-effectiveness of a new short-stay unit to “rule out” acute myocardial infarction in low risk patients. J Am Coll Cardiol 1994;24:1249 –59. 6. Graff LG, Dallara J, Ross MA, et al. Impact on the care of the
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7. 8. 9.
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emergency department chest pain patient from the Chest Pain Evaluation Registry (CHEPER) study. Am J Cardiol 1997;80: 563– 8. Farkouh ME, Smars PA, Reeder GS, et al. A clinical trial of a chest-pain observation unit for patients with unstable angina. N Engl J Med 1998;339:1882– 8. Mikhail MG, Smith FA, Gray M, Britton C, Frederiksen SM. Cost-effectiveness of mandatory stress testing in chest pain center patients. Ann Emerg Med 1997;29:88 –98. Previtali M, Lanzarini L, Fetiveau R, et al. Comparison of dobutamine stress echocardiography, dipyridamole stress echocardiography and exercise stress testing for diagnosis of coronary artery disease. Am J Cardiol 1993;72:865–70. Hamm CW, Goldman BU, Heeschen C, Kreymann G, Berger J, Meinertz T. Emergency room triage of patients with acute chest pain by means of rapid testing for cardiac troponin T or troponin I. N Engl J Med 1997;337:1648 –53. Glover CL, Benink E, Tudor G, Aldag J, Smith M. Outcome analysis of chest pain patients discharged from the ED–a pilot study. Am J Emerg Med 2000;18:779 – 83. Kuntz KM, Fleischmann KE, Hunink MG, Douglas PS. Costeffectiveness of diagnostic strategies for patients with chest pain. Ann Intern Med 1999;130:709 –18. Polanczyk CA, Johnson PA, Hartley LH, Walls RM, Shaykevich S, Lee TH. Clinical correlates and prognostic significance of early negative exercise tolerance in patients with acute chest pain seen in the hospital emergency department. Am J Cardiol 1998;81:288 – 92. Steinberg EH, Koss JH, Lee M, Grunwald AM, Bodenheimer MM. Prognostic significance from 10-year follow-up of a qualitatively normal planar exercise thallium test in suspected coronary artery disease. Am J Cardiol 1993;71:1270 –3. Garber AM, Solomon NA. Cost-effectiveness of alternative test strategies for the diagnosis of coronary artery disease. Ann Intern Med 1999;130:719 –28. Beleslin BD, Ostojic M, Stepanovic J, et al. Stress echocardiography in the detection of myocardial ischemia. Circulation 1994;90: 1168 –76.
C. Lai et al. 17. Froelicher ES. Usefulness of exercise testing shortly after myocardial infarction for predicting 10-year mortality. Am J Cardiol 1994;74:318 –23. 18. Legrand V, Raskinet B, Laarman G, Danchin N, Morel MA, Serruys PW. Diagnostic value of exercise electrocardiography and angina after coronary artery stenting. Am Heart J 1997;133:240 – 8. 19. Kirk JD, Turnipseed S, Lewis WR, Amsterdam EA. Evaluation of chest pain in low-risk patients presenting to the emergency department: the role of immediate exercise testing. Ann Emerg Med 1998;32:1–7. 20. Diercks DB, Gibler WB, Liu T, Sayre MR, Storrow AB. Identification of patients at risk by graded exercise testing in an emergency department chest pain center. Am J Cardiol 2000;86:289 – 92. 21. Ferreiros ER, Boissonnet CP, Pizarro R, et al. Independent prognostic value of elevated C-reactive protein in unstable angina. Circulation 1999;100:1958 – 63. 22. de Lemos JA, Morrow DA, Bentley JH, et al. The prognostic value of B-type natriuretic peptide in patients with acute coronary syndromes. N Engl J Med 2001;345:1014 –21. 23. Omland T, Persson A, Ng L, et al. N-terminal pro-B-type natriuretic peptide and long-term mortality in acute coronary syndromes. Circulation 2002;106:2913– 8. 24. Sabatine MS, Morrow DA, de Lemos JA, et al. Multimarker approach to risk stratification in non-ST elevation acute coronary syndromes: simultaneous assessment of troponin I, C-reactive protein, and B-type natriuretic peptide. Circulation 2002;105:1760 –3. 25. Enguidanos ER, Rosen P. Language as a factor affecting follow-up compliance from the emergency department. J Emerg Med 1997; 15:9 –12. 26. Mouton CP, Beaudouin R, Troutman A, Johnson MS. Barriers to follow-up of hypertensive patients. J Health Care Poor Underserved 2001;12:290 –301. 27. Magnusson AR, Hedges JR, Vanko M, McCarten K, Moorhead JC. Follow-up compliance after emergency department evaluation. Ann Emerg Med 1993;22:560 –7.
doi:10.1016/S0736-4679(03)00238-5
Original Contributions
SHORT-TERM RISK AFTER INITIAL OBSERVATION FOR CHEST PAIN Christopher Lai,
MD,*
Thomas P. Noeller,
MD,*
Kristen Schmidt, Emerman, MD*
MD,*
Peter King,
MD,†
and Charles L.
*Department of Emergency Medicine, Cleveland Clinic Foundation, Cleveland, Ohio, and †Department of Emergency Medicine, Ohio Permanente Medical Group, Cleveland, Ohio Reprint Address: Charles L. Emerman, MD, Department of Emergency Medicine, Cleveland Clinic Foundation, 9500 Euclid Avenue/E19, Cleveland, OH 44195
e Abstract—Few studies have evaluated the necessity of immediate stress testing after observation for chest pain. The purpose of this study was to assess the safety of outpatient stress testing after discharge from a chest pain unit. We hypothesized that discharge from a chest pain unit before stress testing is associated with a low rate of shortterm adverse outcomes. This was a retrospective chart review of managed care patients discharged from the chest pain unit before the performance of stress testing. Records were reviewed for the occurrence of adverse cardiac outcomes before an outpatient stress test up to 60 days postdischarge. Primary outcomes were defined as death or myocardial infarction, and secondary outcomes as readmission for chest pain evaluation, unstable angina, or congestive heart failure. Three hundred forty-four patients were identified. One hundred sixty-six patients had either a recent prior stress test (17) or an outpatient test (149) performed within 60 days of discharge. During that time, 2 patients (0.6%) had a fatal out-of-hospital cardiac event, and there were 27 subsequent chest pain visits to the Emergency Department by 24 patients (7.0%). Nine patients (2.6%) were admitted to the hospital and 10 (2.9%) were readmitted to the observation unit for chest pain. We conclude that patients who have negative serial electrocardiograms and enzyme testing in a chest pain unit are at low risk for shortterm cardiac events. Appropriately selected patients may be discharged for subsequent outpatient testing. © 2003 Elsevier Inc.
INTRODUCTION Chest pain accounts for 5– 6 million visits to Emergency Departments (EDs) across the country every year and can be associated with coronary artery disease, the leading cause of death in the United States (1,2). Approximately 2% of patients with acute coronary syndromes are mistakenly discharged from the ED (3). With the additional benefit of a chest pain observation unit, the ED can decrease the number of missed myocardial infarctions without utilizing scarce hospital resources for low risk patients (4 – 6). Although there are differences in chest pain protocols, observation units generally follow a strategy to identify myocardial infarction (MI), unstable angina, and exercise-induced ischemia. After an MI has been ruled out by serial cardiac marker measurements and electrocardiography (EKG), a stress test may be done to evaluate cardiac risk and determine the need for further intervention. A negative stress test indicates a low risk of shortterm adverse cardiac events, whereas a positive result indicates higher risk and the need for more aggressive intervention (7–9). Providing stress tests every day of the week requires substantial resources. Because short-term risk after discharge from a chest pain unit without a stress test has not been well defined, it is not clear whether that commitment of resources is necessary. The purpose of this study
e Keywords— chest pain; observation; emergency service; hospital; exercise test; myocardial infarction
RECEIVED: 1 May 2002; FINAL ACCEPTED: 8 April 2003
SUBMISSION RECEIVED:
28 February 2003; 357
358
C. Lai et al.
was to evaluate the short-term safety of discharging observation unit patients after serial markers and EKGs with referral for further outpatient assessment and stress testing.
MATERIALS AND METHODS This was a retrospective chart review of patients admitted to our observation unit for chest pain evaluation on a Friday or Saturday from January 1998 to December 2000. Because these patients were discharged on the weekends when no stress testing was immediately available, they were routinely referred to their primary care provider (PCP) for follow-up evaluation and stress testing. Patients were identified by a search of the observation unit admission and discharge logs for diagnoses of chest pain, unstable angina, and “rule-out MI.” We limited our search to patient members of one managed care plan (Kaiser Permanente) with the expectation that complete follow-up data would be available. Patients were included only if they had information available in the managed care plan or hospital records to determine their 60-day outcome. Data were abstracted by a single reviewer using a standardized data collection form. The Cuyahoga County Coroner’s records were reviewed for any patients in whom 60-day outcome could not be determined from the managed care database or hospital records. Patients were excluded if they were admitted to the hospital from the observation unit for any reason at the index visit or if they had a stress test during this index visit. For patients with multiple ED visits, only the first one was considered. In the observation unit, patients underwent serial EKG and cardiac enzyme testing every 4 h for a total of 12 h while on continuous cardiac monitoring. The EKGs were over-read at the time by a cardiologist and subsequently categorized by one of the investigators who was blinded to the clinical data. Our experience is that 1% to 2% of patients will “rule-in” during observation unit evaluation. Patients who were felt to be high risk by the treating physician were admitted if it was felt to be unsafe to discharge the patient before stress testing. Patients who were discharged on the weekends were scheduled for outpatient testing at the discretion of the treating physician. The patients’ prior and subsequent cardiac evaluation, including stress tests or catheterization, were reviewed and categorized. The primary outcome was defined as death or MI within 60 days of discharge or before outpatient stress testing. Secondary outcomes included repeat visits resulting in hospital or CDU admission for chest pain, unstable angina, or congestive heart failure. Events that
Table 1. Study Demographics Descriptor
Cardiac event (%)
No cardiac event (%) p value
Age (years) 57.9 ⫾ 13.6 Gender Male 44.8 Race Caucasian 23.9 Risk factors Prior CAD 26.6 Prior MI 13.4 Prior revascularization 12.5 Hypertension 100 Diabetes 24.8 Hyperlipidemia 32.8 Cigarette use 24.2
60.3 ⫾ 13.3
⬍ 0.05
44.4
ns
33.3
ns
66.7 11.1 11.1 66.8 33.3 33.3 11.1
⬍ 0.05 ns ns ns ns ns ns
CAD ⫽ coronary artery disease; MI ⫽ myocardial infarction.
occurred during the index visit were not included. Stress test results were based on cardiology or radiology staff interpretations as documented in the medical record. An abnormal stress test was defined by the presence of findings indicating stress-induced ischemia. Follow-up data were obtained from review of the managed care organization and hospital records. Data were reviewed for patient demographics, details of the chest pain evaluation, 60-day outcomes, and stress testing. Descriptive data are presented as means and standard deviations, or as proportions. Fisher’s exact test or Students t-test was used as appropriate, and a p value less than 0.05 was considered statistically significant. This study was approved by the IRB of both the hospital and the managed care organization, and was in accordance with the Declaration of Helsinki. RESULTS Four hundred and forty-two patients were identified, of whom 98 were excluded for the following reasons. Thirty-one of the excluded patients were kept beyond 24 h and underwent stress testing the next day, 30 patients were admitted to the hospital, 19 visits were duplicate entries or repeat visits, 8 patients were misidentified in the log and were not observed for cardiac evaluation, 5 patients had an insurance change and were not in the Kaiser system, and 5 patients were otherwise lost to follow-up. Three hundred forty-four patients met study criteria. Patients were 19 to 95 years of age (mean 59.6, SD 13.7) (Table 1). One hundred fifty-four (44.8%) patients were male. Approximately 73.8% of the patients were African American, 24.1% were white, and 2.1% were listed as other. The most frequently documented cardiac risk fac-
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359
Table 2. Outcome of Observation Unit Care Category Observation Unit Discharge Dx
Follow-up Follow-up study
Results
Subject
Number
%
Non-cardiac chest pain Reflux Musculoskeletal Angina Unstable angina Other Number with PCP Average days after ED visit # with repeat ED visits Exercise stress Stress thallium Stress echocardiography Catheterization Normal Abnormal Indeterminate
248 35 34 5 1 21 190 9 24 85 50 10 4 103 24 22
72.1 10.2 9.9 1.5 0.3 6.1 55.2 7.0 24.7 14.5 2.9 1.2 69.1 16.1 14.8
tor was hypertension (67.7%), followed by hypercholesterolemia (32.8%) and known coronary artery disease (CAD) or angina (27.6%). Two hundred forty-nine patients (72.4%) did not have a prior history of CAD. Forty-three patients (12.5%) had a previous coronary artery bypass graft (CABG) or stent placement and 46 patients (13.4%) had a previous MI. The most common chief complaint was chest pain (86.9%). The majority of EKGs were categorized as non-specific ST-T wave changes (41.9%), followed by normal (36.9%) and old infarction (5.8%). The most common chest pain observation unit discharge diagnosis was noncardiac chest pain (72.1%) followed by gastroesophageal reflux (10.2%) and musculoskeletal pain (9.9%) (Table 2). In follow-up, 190 patients (55.2%) visited their PCP within an average of 9 (range 2–38) days after the index visit. One hundred forty-nine patients (43.3%) had a
Figure 1. Results of follow-up stress testing.
stress test. In total, 295 patients (85.8%) followed up with their PCP or had a stress test. The stress tests were performed an average of 22 ⫾ 15 days after the ED visit. The most frequent type of evaluation was exercise stress testing, followed by stress thallium, stress echocardiography, and catheterization (Table 2). The results are displayed in Figure 1. One hundred sixty patients (46.5%) had records of a prior cardiac evaluation (Figure 2). One hundred nine of these tests (31.7%) were normal, 35 (10.2%) were abnormal, 15 (4.4%) were indeterminate, and the result of 1 study (0.3%) was unknown. Only 34.3% of patients with a prior stress test had another stress test performed within the follow-up period compared with 51.1% of patients with no prior stress test (p ⫽ 0.002). Those with a history of an exercise treadmill test were most likely to have a study in follow-up (43.9%) compared with the least likely group, those who had a prior nuclear imaging test (18.2%; p ⫽ 0.008). Of the 195 patients who did not have an outpatient stress test, the emergency physician determined that 18 patients (5.2%) did not require one, and the PCP or cardiologist determined 79 patients (23.0%) did not require one. Nineteen patients (5.5%) refused a stress test. Seventeen patients (4.9%) had a recent stress test and 13 patients (3.8%) had a stress test scheduled after the 60-day period. Forty-nine patients (14.2%) did not follow up with their PCP. In follow-up, there were 27 return visits by 24 patients (7.0%) to the ED for chest pain. After the second visit, 5 patients were discharged home, 10 were admitted to the CDU, and 9 were admitted to the hospital (Table 3). None of these patients had a myocardial infarction. Eight patients had cardiac evaluation during this admission. Four had normal results, three had abnormal results, and one was indeterminate. Two patients died during the follow-up period as a
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C. Lai et al.
Figure 2. Patients with prior cardiac evaluations.
result of out-of-hospital cardiac arrest. One of these arrests occurred 4 days after discharge, whereas the other occurred 49 days after discharge after several outpatient and ED evaluations. The primary outcome of death or MI was, therefore, documented in 2 (0.6%; 95% CI 0.1–2.1%) of the patients and the secondary outcome occurred in 19 (5.5%, 95% CI 3.4 – 8.5%) patients.
DISCUSSION We found that patients monitored in a chest pain observation unit have a low likelihood of significant cardiac events up to 60 days after discharge. This finding is consistent with other reports that patients evaluated with serial cardiac markers are at low risk for early adverse outcomes (5,10,11). Most previous studies have evaluated the short-term risk after observation unit-based stress testing. Patients discharged after a negative stress test have a low likelihood of subsequent cardiac events and few repeat ED
Table 3. Outcomes
Primary Death MI Secondary (Revisits) Discharged CDU Admitted CHF UA CP
#
%
95% CI
2 0
0.6 0
0.1–2.1 0.0–1.1
5 10 9 1 4 4
1.5 2.9 2.6 0.3 1.2 1.2
0.5–3.4 1.4–5.3 1.2–4.9 0.1–1.6 0.3–3.0 0.3–3.0
MI ⫽ myocardial infarction; CDU ⫽ ; CHF ⫽ congestive heart failure; UA ⫽ ; CP ⫽ .
visits and admissions (12–15). Even in patients who have had previous cardiac complications such as MI, angioplasty, or stent placement, a negative stress test implies a benign short-term course (16 –18). Mikhail et al. performed stress tests on 424 patients initially evaluated in their observation unit. None of the 400 (94%) patients with a negative stress test had a cardiac event within 14 days (8). Kirk et al. followed patients with a negative or non-diagnostic exercise stress test for 30 days and documented no cardiac events. Moreover, patients with a positive stress test had no documented cardiac mortality, although 10.7% of these patients returned to the ED within 30 days (19). Polanczyk et al. found a 17% re-visit rate among patients with a negative stress test, compared with 7% of our patients with no stress test. In their study, 2% of those with a negative exercise stress test experienced a cardiac event within 6 months, including MI, coronary artery bypass graft, and angioplasty (13). Diercks et al. reported a 1-year cardiac complication rate of 1.1% (including coronary artery bypass graft, percutaneous transluminal angioplasty, cardiogenic shock, ventricular fibrillation/tachycardia arrest, and myocardial infarction) for patients with a negative exercise stress test, compared with 36.8% in those with a positive test (20). Although the rate of death or MI in our study may be as high as 2.1%, the safety of discharging patients from the CDU without immediate stress testing seems comparable to an approach that includes immediate stress testing. It is unknown whether an immediate stress test would have prevented the two fatal events. It can be theorized that immediate stress testing might decrease the rate of return visits for chest pain or decrease the rate of admission for those returning, but further study is needed in this area. The potential benefits of discharging patients without immediate stress testing are somewhat institution-spe-
Short-term Risk After Chest Pain
cific. Availability of stress tests based on hospital resources and stress laboratory schedules will dictate how many tests are available for ED patients each day. Length-of-stay in the observation unit would be decreased if the patient is discharged once the “rule-out” protocol is completed without the need to wait for a stress test. Stress testing is just one tool used by clinicians for risk-stratification in a chest pain unit. In addition to a careful history that includes screening for traditional risk factors, consideration might be given to measurement of total cholesterol if not documented by the patient’s PCP. This is an opportunity to take advantage of a “teachable moment.” If the total cholesterol, HDL, LDL, or triglycerides are abnormal, patients are at higher risk for adverse outcomes and can be appropriately counseled and referred. Serum markers of inflammation such as C-reactive protein (CRP) have recently been incorporated as riskstratification tools in some, particularly high-risk, patient populations (21). Inflammation is increasingly recognized as a significant phenomenon in acute coronary syndromes. There are, as yet, no clear guidelines on the acute management of CDU patients with an elevated CRP compared to those with a normal CRP. However, it is clear that those with abnormal elevations are at higher risk for adverse outcomes and may be candidates for more aggressive interventions and certainly close followup, including risk factor modification. Elevated B-type natriuretic peptide (BNP), commonly measured now in patients with congestive heart failure, has been associated with a worse prognosis in patients with acute coronary syndromes (22,23). A “multimarker” approach incorporating troponin, CRP, and BNP recently has been shown to stratify risk for both short- and long-term outcomes in patients with ACS (24). The focus of the emergency physician is on the detection of an acute coronary event, but patients in a chest pain unit are excellent candidates for risk factor assessment that may help with acute decisions as well as with appropriate referral and risk-factor modification. The availability of follow-up is a critical issue in determining the safety of delayed stress testing. This study examined a managed care population, all of whom had an assigned PCP. About 86% of patients in our study received follow-up by 60 days, either with a stress test or by a visit to their doctor. Whether this would occur in another environment is unknown. In fact, having a primary physician is the most important factor in determining the likelihood that a patient will follow up (25). Lack of insurance and worries about cost have been cited as barriers to follow-up in other settings (26). Prior studies have evaluated other strategies to enhance follow-up,
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including contact with the PCP and direct scheduling of outpatient appointments (27). Our study is limited by the small number of patients and the retrospective nature of this review. Confidence intervals around adverse event rates would be tighter if a larger group of patients was included. However, the overall event rate is consistent with that found in other studies evaluating chest pain unit follow-up. A formal risk-stratification scheme was not used to determine suitability for discharge. Rather, the decision to admit or discharge for outpatient follow-up was left to the discretion of the attending physician. Utilization of a riskstratification score to help determine suitability for immediate vs. outpatient stress testing is a focus of current research. The study population was derived from a single center caring for members of a managed care plan, which may have a different spectrum of cardiac disease than other ED populations. The managed care plan used in this study, however, enrolls a broad spectrum of patients. The age and ethnicity of the study sample, for example, is typical of an urban population seen in many EDs. Because these patients have primary care providers, it can be reasoned that they are more likely to follow up than others such as the uninsured. The safety of discharging patients from a CDU without stress testing is likely to be realized only in a group of patients who are likely to follow up.
CONCLUSION Patients discharged from a chest pain observation unit after appropriate evaluation, including serial electrocardiography and serum cardiac marker measurements, are at low short-term risk for adverse cardiac outcomes. Appropriately selected patients may be discharged for early follow-up and outpatient evaluation.
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