Exercise Testing in Chest Pain Units Rationale Implementation and Results

Ezra A. Amsterdam, MD, FACCa*, J. Douglas Kirk, MD, FACEPb, Deborah B. Diercks, MDb, William R. Lewis, MD, FACCa, Samuel D. Turnipseed, MDb aDepartment of Internal Medicine, University of California School of Medicine (Davis) and Medical Center, 4860 Y Street, Suite 2820, Sacramento, CA 95817, USA bDepartment of Emergency Medicine, University of California School of Medicine (Davis) and Medical Center, 4150 V Street, PSSB Suite 2100, Sacramento, CA 95817, USA

Although new diagnostic approaches have enhanced the evaluation of patients presenting to the emergency department (ED) with chest pain, this syndrome remains a major clinical challenge [1]. This symptom accounts for more than 8 million ED visits per year in this country, accounting for more than 2 million hospital admissions at a cost of $8 billion for presumed acute coronary syndrome (ACS) [2]. However, a coronary event is actually confirmed in only a minority of these patients [3]. This population poses a dilemma to the clinician of inadvertent discharge of those with a life-threatening condition versus unnecessary admission for a benign process with its associated expense and the potential risks of further tests. A low threshold for admission of these patients was advocated early in the coronary care unit (CCU) era by the admonition that ''patients should be admitted to the CCU solely on suspicion of having a myocardial infarction'' [4]. This approach has persisted because of the focus on patient welfare as well as the litigation potential of missed ACS [5]. Inadvertent discharge of patients with ACS persists at a rate of 4% to 5% and the mortality and morbidity of this group are substantial [6]. However, a consequence of the low threshold for admission has been large numbers of unnecessary hospitalizations, suboptimal

* Corresponding author. E-mail address: [email protected] (E.A. Amsterdam).

patient management, and inefficient resource use. This problem is reflected by the recent demonstration that an appreciable number of patients with coronary artery disease (CAD) who present with acute chest pain respond to proton pump inhibitors, reflecting the gastrointestinal cause of their symptoms [7].

The development of chest pain units (CPUs) is a response to the need for a strategy to effect accurate, safe, and cost-effective management of patients presenting with possible ACS. Although their initial purpose was to facilitate rapid coronary reperfusion therapy, these units have evolved into centers for management of the lower risk population that composes the majority of patients presenting with chest pain. The latter include those without initial, objective evidence of myocardial ischemia/ infarction in whom accelerated risk stratification can identify those requiring admission and those who can be safely discharged with outpatient follow-up [8-15]. A basic element of this accelerated diagnostic protocol (ADP) is stress testing after a negative initial assessment for myocardial infarction (MI) or unstable angina. The primary method of testing has been treadmill exercise electrocardiography (ECG) in the context of the ADP. Fundamental to this approach is the identification of patients with low clinical risk on presentation to the ED.

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