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Impact of a Negative Evaluation for Underlying Coronary Artery Disease on One-Year Resource Utilization for Patients Admitted With Potential Acute Coronary Syndromes

Posted on: Thursday, 16 December 2004, 03:00 CST

Abstract

Reduction in emergency department (ED) overcrowding is a major Joint Commission on the Accreditation of Health-care Organizations (JCAHO) initiative. One major source of ED overcrowding is patients waiting for telemetry beds. Objective: To determine whether, in patients admitted with a potential acute coronary syndrome, a negative evaluation for underlying coronary artery disease would reduce ED and hospital revisits over the subsequent year compared with patients who did not receive an evaluation for underlying coronary artery disease. Methods: Nine hundred ninety-nine consecutive patients admitted for potential acute coronary syndromes through the ED during a one-year period were screened for inclusion. Patients who had a negative evaluation for underlying coronary disease were compared with patients who were not evaluated for underlying coronary artery disease for subsequent ED visits, hospital admissions, and cardiac resource utilization over the year following the index visit via a health system-wide computerized record review. Patients with positive tests or biomarkers at the index visit were excluded. Each repeat visit was rated as "potentially cardiac" or "noncardiac." Results of echocardiograms, stress tests, and catheterizations and information about in- hospital deaths were obtained. Results: Six hundred ninety-two patients met the inclusion criteria: 556 patients received no evaluation for underlying coronary artery disease, 116 had a negative stress test, and 20 had a negative cardiac catheterization during the index visit. Patients with no evaluation for underlying coronary artery disease and patients with a negative evaluation had similar likelihoods of a repeat ED visit (negative test 39.0% vs. no test 40.3%; p = 0.85) and repeat hospital admission (28.7% vs. 31.5%; p = 0.61). The rates of a potentially cardiac-related ED visit (21.3 vs. 23.4%; p = 0.65) and hospital admission (17.7% vs. 20.7%; p = 0.48) were not significantly different. The two populations had similar utilization rates of echocardiograms, stress tests, and catheterizations (p > 0.70 for all). Conclusions: For patients admitted to the authors' institution with a potential acute coronary syndrome, there was no association between a negative evaluation for underlying coronary artery disease and overall or potentially cardiac ED visits, admissions, or cardiac resource test utilization over the year following the index visit. Key words: recidivism; emergency department; stress test; cardiac catheterization. ACADEMIC EMERGENCY MEDICINE 2004; 11:1272-1277.

In the United States, there are approximately six million emergency department (ED) visits each year for chest pain.1 Up to two-thirds of these patients are admitted, most of whom do not have acute cardiac pathology.2 Numerous studies have attempted to identify a low-risk group of patients who can be safely and immediately discharged home by using cardiac markers, clinical algorithms, cardiac imaging, neural networks, or combinations of these strategies.3-11 To date, no single strategy has been created with sufficient sensitivity and plausibility to be widely implemented.

Emergency department overcrowding, tightening budgets, and limited personnel resources necessitate new approaches to inefficient care. One major cause of ED overcrowding is the poor availability of inpatient beds. Since a large percentage of patients awaiting inpatient beds are being "ruled out" for acute coronary syndromes, it seems reasonable to evaluate strategies that could expedite the inpatient evaluation of this patient population. One possibility is transitioning traditional inpatient testing (such as stress tests) to the outpatient setting. Chan et al. demonstrated that compared with outpatient testing, inpatient stress testing did not impact 30-day cardiovascular outcomes.12 Thus, they concluded that stress testing could be safely deferred to the outpatient setting. However, it remains to be seen whether inpatient testing may have other beneficial effects, such as reduced ED or hospital recidivism rates and decreased future resource utilization.

In the present study, we investigated whether patients admitted for a potential acute coronary syndrome who received a negative inpatient evaluation for underlying coronary artery disease (CAD) had reduced rates of subsequent ED visits, hospital admissions, and cardiac resource utilization over a oneyear follow-up period, compared with patients who did not receive an evaluation for underlying CAD.

METHODS

Study Design. We conducted a prospective cohort study of patients admitted to the hospital with a potential acute coronary syndrome to determine whether patients who received an inpatient evaluation for underlying CAD were less likely to have subsequent ED visits, repeat hospitalizations, or cardiac resource utilization than patients who did not undergo such testing. This was a substudy of a larger investigation approved by the University of Pennsylvania Committee on Research Involving Human Subjects.

Study Setting and Population. Study subjects were patients who presented to the ED from March 1, 2001, to March 1, 2002, at an academic, urban, tertiary care hospital and were subsequently admitted for evaluation of a potential acute coronary syndrome. The ED had an annual census of approximately 50,000 adult visits. All ED patients >24 years of age who presented with chest pain and received an electrocardiogram were screened for inclusion. All patients discharged or who left against medical advice from the ED were excluded from the analysis. Patients with a positive test for underlying CAD during the hospital admission (stress or catheterization), who had a final diagnosis of unstable angina or acute myocardial infarction (AMI), or who died in the hospital were excluded from the study.

Study Protocol. Trained research assistants were present in the ED 16 hours a day, seven days a week. They prospectively enrolled patients and ensured that the treating physician completed a standardized data collection form.13 Collected data included demographics, characteristics of the chest pain, cardiac risk factors (hypertension, family history, diabetes mellitus, tobacco, hyperlipidemia), cocaine use, cardiac history, vital signs, physical examination (jugular venous distention, murmur, rales), treatments, and patient disposition. Patients' hospital courses were followed daily and information about complications and interventions was recorded. One-year information was obtained via the medical record search using computerized ED and inpatient medical records, as well as cross-checking the study logs for patients who repeatedly presented to the ED. No attempt was made to influence testing or treatment strategies while the patient was in the hospital.

Measures

Index Visit. The hospital course was followed daily by one of the investigators. Complications (arrhythmias, hypotension, congestive heart failure, delayed MI, cardiopulmonary resuscitation, death); interventions (percutaneous coronary interventions, coronary artery bypass grafting); and results of diagnostic testing were recorded as they occurred.

Each presenting electrocardiogram was characterized by the treating physician in regard to ST elevation, ST depression, T-wave inversion, hypertrophie T waves, pathologic Q waves, left bundle branch block, and right bundle branch block.

Acute myocardial infarction was defined in accordance with the European Society of Cardiology criteria.14 A diagnosis of AMI was made if the patient had an elevation of cardiac troponin I ≥2 ng/mL or creatine kinase-MB (CK-MB) enzyme ≥10 ng/mL. Unstable angina was considered to occur if there was documented reversible ischemia on stress test, coronary artery occlusion ≥70% in at least one vessel as seen during cardiac catheterization, or elevations of cardiac enzymes above laboratory normal but below levels necessary for diagnosis of AMI (troponin I ≥0.4 ng/mL but <2 ng/mL; CK-MB ≥ 5 ng/mL but <10 ng/mL).15

Follow-up. The investigators searched our health system's computerized charting record for every patient. Any visit to the ED or any hospital admission was reviewed and categorized as "potentially" cardiac or noncardiac. ED visits were considered "potentially" cardiac if the presenting complaint included chest pain, shortness of breath, syncope, or an anginal equivalent that caused the treating physician to initiate a cardiac evaluation. Hospital admissions were rated in the same manner. Determination of a potentially cardiac visit included review of electrocardiograms, biochemical markers, echocardiograms, stress testing, cardiac catheterizations, and admissions to a cardiac service. Admission and discharge dates were noted for every admission. A sample of repeat visits was reviewed by two chart abstractors independent of each other's rating (n = 30). There was 100% interrater agreement for determination of whether a given ED visit or admission was potentially cardiac or noncardiac, as defined above (κ = 1.0).

Echocardiograms were reported as positive or negative for likely underlying CAD based on the presence or absence of regional wall- motion abnormalities. At our institution, a variety of str\ess testing is available and utilized. Exercise treadmill tests were conducted with echocardiography or nuclear imaging. Chemical stress tests were induced with dobutamine or dipyridamole. Imaging was completed with technetium-99 sestamibi; resting and stress images were obtained and compared. The test was considered positive if there was a reversible perfusion defect or new wall-motion abnormality under stress. Cardiac catheterization was considered positive if coronary angiography revealed at least one vessel with more than 70% occlusion.

Data Analysis. All information was entered into a Microsoft Access database (Microsoft, Redmond, WA). Fisher's exact tests were performed to compare the negative test and nontested cohorts for each recorded outcome. Chi-square tests were performed on data sets with multiple variables to test for significance, and two-sided p- values were recorded. A value <0.05 was considered statistically significant.

RESULTS

There were 999 patients admitted to the hospital for evaluation of potential acute coronary syndrome during the study period. Of those, 692 met inclusion criteria: 116 patients had a negative stress test; 20 patients had a negative cardiac catheterization during their index visit, and 556 did not receive an evaluation of underlying CAD with either of these two tests. The two groups were similar in regard to demographics, presentation, electrocardiographic findings, and cardiac risk factors (Table 1).

Patients who initially received an evaluation for underlying CAD and had a negative catheterization or a stress test were similar to the patients who did not receive an evaluation for underlying CAD with respect to presenting symptoms, factors, and initial electrocardiographic findings.

With respect to our main outcomes (Table 2), patients who received an evaluation for underlying CAD were not different from patients who did not receive an evaluation. Overall, a total of 277 patients returned to the ED at least once (range 1-18) and 214 patients were admitted to the hospital at least once (range 1-14) in the year following their index hospitalization. There was no difference between the groups with respect to the presence of at least one or more ED visits (negative testing 39.0% vs. no testing, 40.3%; p = 0.85), or at least one repeat hospital admission (28.7% vs. 31.5%; p = 0.60).

For potentially cardiac repeat visits, 159 patients returned to the ED and 139 were admitted to the hospital one or more times. There was no difference between the groups with respect to at least one potentially cardiac return ED visit (negative testing 21.3% vs. no testing 23.4%; p = 0.65) or at least one potentially cardiac hospital admission (17.7% vs. 20.7%; p = 0.48).

TABLE 1. Patient Characteristics

With respect to duration before the first return ED visit [negative testing 129 days (85-174) vs. no testing 124 days (105- 144); p = 0.83] or first repeat admission [128 (82-175) vs. 140 days (119-160); p = 0.65], the two groups were also not significantly different (Figure 1).

In terms of resource utilization subsequent to the index visit, the two groups were nearly identical: the frequencies of inpatient echocardiograms (negative testing 50% vs. no testing 50%; p = 1.0), stress tests (21% vs. 22%; p = 1.0), and cardiac catheterizations (12.5% vs. 10.4%; p = 0.72) were not different.

TABLE 2. Main Outcomes

DISCUSSION

An American Hospital Association survey reported that approximately 79% of urban EDs were at or above capacity in 2002.16 Methods to reduce ED overcrowding are needed. One potential option is to expedite the release of inpatients so that these beds will be more rapidly available for new admissions. A high percentage of ED patients awaiting inpatient beds require telemetry. Therefore, expeditious transitioning of "rule-out"-acute-coronary-syndrome patients to the outpatient setting for further diagnostic testing would be expected to improve patient flow through the telemetry services. Previous studies indicate that a negative stress test has good negative predictive value for cardiac events over 12 months, is cost-effective, and can be performed using a variety of methods.17- 21 In spite of this, there still remains a significant proportion of patients admitted for potentially cardiac chest pain who do not receive such inpatient testing, 70% in some populations.12

There are two main reasons why inpatient stress testing might be beneficial. One is safety. Some investigators, such as Manini et al., have suggested that subsets of patients who receive inpatient stress tests have lower complication rates than those scheduled for outpatient tests.22 Others, such as Chan et al, found that an inpatient stress test did not reduce 30day cardiovascular complication rates and have suggested that expedited outpatient evaluation is just as safe.12 Another potential reason why inpatient testing might be preferable is that it may reduce return ED and hospital visits, particularly in the group of patients found not to have underlying cardiovascular disease. Our study found that this is not the case. We found that patients with a negative evaluation for underlying CAD were just as likely as patients without any evaluation to return to the ED, to be readmitted to the hospital, and to utilize a variety of cardiovascular resources over the year following the index visit.

Relatively few other studies have looked specifically at ways to reduce recidivism among chest pain patients. DeFilippi et al.23 compared cardiac catheterization with stress testing for CAD in low- risk patients, but also included data concerning return rates. They found that patients with a negative catheterization had significantly fewer return ED visits (10% vs. 30%; p < 0.001) and admissions (3% vs. 16%; p = 0.003) for chest pain than patients with a negative or nondeterminate electrocardiographic exercise treadmill test. Based on this study, in which all patients received diagnostic testing, the authors suggested that there would be a potential long- term cost effectiveness of early invasive diagnostic strategy for low-risk patients with chest pain. Unfortunately, they did not include a control group that did not receive catheterization or stress testing-the largest group of low-risk patients in most institutions. Our study extends their results by comparing patients who received their least invasive strategy (stress testing) with patients who did not receive any testing.

Shoyeb et al.24 compared patients who received a stress test or catheterization with patients who did not during an index visit. A protocol-driven riskstratification system was used to determine which patients were tested; 47% of their "intermediate-risk" population received a stress test and/or catheterization. The comparison groups included patients who had a positive diagnostic evaluation during their index visits. Using a short-term end point (three months), they found that patients with completed testing had a lower number of return ED visits for chest pain, reduced nonfatal MI, and decreased mortality. Our study suggests that their end point may have been too soon. We found that the average duration of time before a repeat visit (ED or admission) was just over 120 days. Therefore, they likely missed most of the repeat visits.

In contrast to both previous studies, we also used a broader definition of potentially cardiac visits, rather than depend on the presence of chest pain as the presenting chief complaint. Many other complaints and clinical scenarios compel physicians to initiate cardiac evaluations, and we attempted to incorporate those complaints into our review.

Figure 1. Return rates of patients who had negative test results compared with patients who did not have testing over the year following the index visit.

Our study prospectively identified consecutive patients with chest pain and selected a cohort that had a negative stress test or negative catheterization during their index visits. Over the course of the next year, we did not observe the expected differences between that group and patients who did not receive such testing. There are likely multiple reasons for our findings. The most simple and obvious is that the reassurance of having a negative test may not be sufficient to prevent patients from returning to the ED over the course of a year.

Second, our patient population has generally low socioeconomic status and low educational level. These patients may have reduced access to health care. It is likely that this population returns to the ED for multiple aspects of their medical care, regardless of the presence or absence of previous test findings. Conducting inpatient cardiac testing may also remove an incentive for patients to follow up with a primary care physician or cardiologist.

LIMITATIONS

This study has limitations that might affect the results. The study was conducted in an urban, inner-city academic hospital; therefore, the results may or may not be applicable to different patient populations. Factors such as socioeconomic status, educational level, and access to other health care options may have a direct influence on recidivism patterns and ED utilization. Other health care settings should be explored to see whether our results are applicable to different populations, including observation units that have the capability to perform stress testing prior to discharge from the ED. Studies conducted within those specific settings could also be useful for future utilization trends and triage decisions.

Given the numbers included in our study, we would be able to detect a difference of just over 10% between the two groups. If the difference were smaller, it could still be significant on a large scale. A decrease of just 5% may mean significantly fewer ED visits each year in the United States. However, this translates to a miniscule clinical difference within any given ED-a reduction of one patient \per day would not help ED overcrowding. Further investigation is justified to determine whether such a small percent change would be worth the cost of a large number of inpatient stress tests and/or invasive diagnostic evaluations.

Finally, we were able to examine follow-up records only from our own institution. Potential missed visits to outside hospitals may be distributed in equal proportions between our two study groups, but there was no way for us to validate this. It is also possible that patients with a negative evaluation may exhibit different behavior from those not evaluated. Patients with a negative evaluation may be less likely to seek nonurgent outpatient care since they have been reassured regarding the lack of serious condition. Alternatively, they might be more likely to seek nonurgent community care based on instructions (or referrals) made at the time of evaluation. Future studies should address these issues.

CONCLUSIONS

We examined the effect of a negative evaluation for underlying CAD on subsequent ED visits, hospital admissions, and cardiac resource utilization. For patients admitted to our institution with a potential acute coronary syndrome, there was no association between a negative evaluation for underlying CAD and overall or potentially cardiac ED visits, admissions, or cardiac resource test utilization over the year following the index visit.

Because we cannot eliminate the possibility that there were undetected differences between the groups of patients who did and did not receive an evaluation for underlying CAD during the index visit, randomized studies can better assess whether an inpatient cardiac evaluation impacts subsequent hospital visits or resource utilization.

References

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11. Limkakeng A Jr, Gibier AB, Pollack C, et al. Combination of Goldman risk and initial cardiac troponin I for emergency department chest pain patient risk stratification. Acad Emerg Med. 2001; 8:696- 702.

12. Chan GW, Sites FD, Shofer FS, Hollander JE. impact of stress testing on 30-day cardiovascular outcomes for low-risk patients with chest pain admitted to floor telemetry beds. Am J Emerg Med. 2003; 21:282-7.

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15. Hollander JE, Mayorga O, Sites FD, Shofer FS. Defining the outcomes of ED chest pain patient risk stratification studies: use of a standardized definition for unstable angina [abstract]. Acad Emerg Med. 2002; 9:375.

16. American Hospital Association. Cracks in the Foundation: Averting a Crisis in America's Hospitals. Chicago: AHA, 2002.

17. Colon PJ 3rd, Guarisco JS, Murgo J, Cheirif J. Utility of stress echocardiography in the triage of patients with atypical chest pain from the emergency department. Am J Cardiol. 1998; 82: 1282-4.

18. Kuntz KM, Fleischmann KE, Hunink MG, Douglas PS. Costeffectiveness of diagnostic strategies for patients with chest pain. Ann Intern Med. 1999; 130:709-18.

19. Garber AM, Solomon NA. Cost-effectiveness of alternative test strategies for the diagnosis of coronary artery disease. Ann Intern Med. 1999; 130:719-28.

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21. Ioannidis JPA, Salem D, Chew PW, Lau J. Accuracy of imaging technologies in the diagnosis of acute cardiac ischemia in the ED: a meta-analysis. Ann Emerg Med. 2001; 37:471-7.

22. Manini AF, Gisondi MA, van der Vlugt TM, Schreiber DH. Adverse cardiac events in emergency department patients with chest pain six months after a negative inpatient evaluation for acute coronary syndrome. Acad Emerg Med. 2002; 9:896-902.

23. deFilippi CR, Rosanio S, Tocchi M, et al. Randomized comparison of a strategy of prcdischarge coronary angiography versus exercise testing in low-risk patients in a chest pain unit: in- hospital and long-term outcomes. ] Am Coll Cardiol. 2001; 37:2042- 9.

24. Shoyeb A, Bokhari S, Sullivan J, et al. Value of definitive

diagnostic testing in the evaluation of patients presenting to the emergency department with chest pain. Am J Cardiol. 2003; 91:1410-4.

Kyle J. Shaver, BS, BA, Robert J. Marsan Jr., BS, Keara L. Sease, MAEd, Frances S. Shofer, PhD, Frank D. Sites, RN, BSN, Judd E. Hollander, MD

From the Department of Emergency Medicine, Hospital of the University of Pennsylvania (KJS, RJM, KLS, FSS, FDS, JEH), Philadelphia, PA.

Received March 8, 2004; revision received March 27, 2004; accepted July 9, 2004.

Supported in part by a grant from the Emergency Medicine Foundation and the Society for Academic Emergency Medicine.

Address for correspondence and reprints: Judd E. Hollander, MD, Department of Emergency Medicine, Ground Floor Ravdin Building, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104-4293. Fax: 215-662-3953; e-mail: jholland@ mail.med.upenn.edu.

doi:10.1197/j.aem.2004.07.007

Copyright Hanley & Belfus, Inc. Dec 2004

Source: Academic Emergency Medicine

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