An economic analysis of an aggressive diagnostic strategy with single photon emission computed tomography myocardial perfusion imaging and early exercise stress testing in emergency department patients who present with chest pain but nondiagnostic electrocardiograms: Results from a randomized trial,☆☆,,★★

Preliminary results presented at the 71st Scientific Session of the American Heart Association, Dallas, TX, November 1998.
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Abstract

Study Objective: Conventional emergency department testing strategies for patients with chest pain often do not provide unequivocal diagnosis of acute coronary syndromes. This study was conducted to determine whether the routine use of single photon emission computed tomography (SPECT) imaging at rest and early exercise stress testing to assess intermediate-risk patients with chest pain and no ECG evidence of acute ischemia will lead to earlier discharges, more discriminate use of coronary angiography, and an overall reduction in average costs of care with no adverse clinical outcomes. Methods: All patients in this study had technetium 99m tetrofosmin SPECT imaging at rest and were randomly assigned to either a conventional (results of the imaging test blinded to the physician) or perfusion imaging–guided (results of the imaging test unblinded to the physician) strategy. Patients in the conventional arm were treated at their physician’s discretion. Patients in the perfusion imaging–guided arm were treated according to a predefined protocol based on SPECT imaging test results: coronary angiography after a positive scan result and exercise treadmill testing after a negative scan result. Study endpoints consisted of total in-hospital costs and length of stay. Hospital costs were calculated using hospital department–specific Medicare cost/charge ratios. Length of stay was calculated as total hospital room days billed (regular and intensive care). Results: We enrolled 46 patients, 9 with acute myocardial infarctions. Patients randomly assigned to the perfusion imaging–guided arm had $1,843 (95% confidence interval [CI] $431 to $6,171) lower median in-hospital costs and 2.0-day (95% CI 1.0 to 3.0 days) shorter median lengths of stay but similar rates of in-hospital and 30-day follow up events as patients in the conventional arm. Conclusion: An ED chest pain diagnostic strategy incorporating acute resting 99mTc tetrofosmin SPECT imaging and early exercise stress testing may lead to reduced in-hospital costs and decreased length of stay for patients with acute chest pain and nondiagnostic ECGs. [Stowers SA, Eisenstein EL, Wackers FJTh, Berman DS, Blackshear JL, Jones AD Jr, Szymanski TJ Jr, Lam LC, Simons TA, Natale D, Paige KA, Wagner GS. An economic analysis of an aggressive diagnostic strategy with single photon emission computed tomography myocardial perfusion imaging and early exercise stress testing in emergency department patients who present with chest pain but nondiagnostic electrocardiograms: results from a randomized trial. Ann Emerg Med. January 2000;35:17-25.]

Introduction

Each year 5 million patients with chest pain are seen in US emergency departments.1 Although the immediate objective for emergency physicians is to identify patients with ST-segment elevation as candidates for initiation of reperfusion therapy for acute myocardial infarction (AMI),2, 3 the great majority of chest pain patients do not have ST-segment elevation or new ST-segment depression4 and pose a diagnostic dilemma.5 Typically, 60% of chest pain patients presenting to the ED are admitted for further cardiac evaluation, although fewer than 15% are proved to have AMIs.6 In addition, initial evaluations in the ED inadvertently miss 4% to 5% of patients with AMI.7, 8

Although the medical history, physical examination, and ECG provide considerable information for short-term risk assessment,9 emergency physicians require additional diagnostic tests for patients who are not initially classified as high risk.5 Several tests including radionuclide myocardial perfusion (single photon emission computed tomography [SPECT]) imaging,10, 11 echocardiography,12 exercise stress testing,13, 14 and assays of creatine kinase MB (CK-MB) isoenzyme and its subforms,15 myoglobin,16 troponin I,17 and troponin T18 are currently used for this purpose.19, 20 SPECT imaging has advantages over several of these technologies because it assesses the functional significance of coronary artery disease, which may not be predicted by coronary anatomy alone,21 has a high sensitivity and specificity for AMI,10, 11, 22 is not time-dependent,23 and has a demonstrated effectiveness in distinguishing patients at high and low risk for cardiac events during the acute phase24 and through 90 days of follow-up.25 Additionally, patients with normal SPECT imaging results and a normal or nondiagnostic exercise ECG have favorable 1-year outcomes.26

Although there is evidence that SPECT imaging in the ED can substantially reduce the number of unnecessary admissions11 and lead to potential cost savings in patients with typical chest pain and nondiagnostic ECGs,11, 27 these earlier results need to be validated with a prospective, randomized clinical trial. The hypothesis of the present study was that the routine use of rest SPECT imaging and early exercise stress testing to assess intermediate-risk patients with chest pain and no ECG evidence of acute ischemia would lead to earlier discharges, more discriminate use of coronary angiography, and an overall reduction in average costs of care with no adverse clinical outcomes. We also hypothesized that these reductions would occur in non-AMI patients and that care for AMI patients would not be negatively affected.

Our study was designed as a cost-minimization analysis and assumed no difference in clinical effectiveness between the 2 diagnostic strategies.28 We also assumed that a rest SPECT imaging diagnostic strategy would only be a viable option for hospitals with high-volume EDs. Thus, the analysis was performed from the hospital’s perspective.

Section snippets

Materials and methods

Patients presenting to the ED of 2 study sites between July 1, 1996, and September 30, 1997, with chest pain believed to be of cardiac origin were evaluated for eligibility to participate. One site was a tertiary care institution in the suburbs of Jacksonville, FL; the other site was an urban hospital with a high percentage of managed care patients. Inclusion criteria were as follows: (1) ongoing chest pain with a duration of less than 12 hours; (2) no ECG ST-segment elevation or depression

Results

A total of 46 patients were enrolled in the study (6% of the 757 unspecified chest pain patients seen at the 2 sites during the enrollment period). Twenty-three patients were randomly assigned to each of the 2 diagnostic arms (conventional and perfusion imaging–guided). For a relatively small sample size, the 2 cohorts were remarkably similar. Mean patient age was similar (58 and 63 years in the conventional and perfusion imaging–guided arms, respectively). Most patients were white, and women

Discussion

The majority of patients who present to EDs with chest pain have normal or nondiagnostic ECG findings. Only about 15% to 17% have an acute coronary syndrome in which salvage of myocardium is time dependent,33, 34, 35 whereas the great majority of these patients have a good prognosis and can be considered for outpatient management. Thus, early risk stratification of patients with chest pain and a nondiagnostic ECG has the potential to improve cost efficacy in those without disease and

Acknowledgements

We thank Linda Davidson-Ray, BA, for management of the cost collection activities; Marian Jones-Richmond, BBA, for construction of the database; Rita Kaurs, MSHSA, and Edward Bernbom, DPM, for their technical assistance and expertise; Kevin J. Anstrom, MS, for his assistance with the statistical analyses, and Kathy B. Gates, BS, for coordination of the core laboratories.

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  • Cited by (0)

    Supported in part by grants from Medi-Physics, Inc, Amersham Healthcare, Arlington Heights, IL.

    ☆☆

    Address for reprints: Eric L. Eisenstein, DBA, Duke University Medical Center Box 3865, Durham, NC 27710; 919-668-8984,fax 919-668-7057; E-mail [email protected].

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