Identifying patients for early discharge: Performance of decision rules among patients with acute chest pain☆
Introduction
Although patients frequently present with symptoms of suspected acute coronary syndrome (ACS), risk stratification remains challenging and inefficient. Although the Thrombosis in Myocardial Infarction (TIMI) risk score and Global Registry of Acute Coronary Events (GRACE) score are recommended to aid risk stratification, they are not sensitive enough to avoid objective testing or inpatient care [1], [2], [3], [4]. Emergency Department (ED) patients with low-risk TIMI and GRACE scores have ACS rates above the acceptable miss rate of 1% [3], [5]. More sensitive rules have been reported, but they identify fewer than 20% of acute chest pain patients for early discharge [6], [7].
The HEART score and North American Chest Pain Rule (NACPR) are recently developed decision rules designed to identify ED patients with symptoms suggestive of ACS for early discharge without objective cardiac testing (stress testing or cardiac imaging). However, both require further validation before prospective implementation [7], [8]. In addition, there is little evidence comparing the clinical utility of these decision rules to each other or to an unstructured clinical evaluation (a clinical assessment based on physician gestalt without the use of a clinical decision rule).
Decision rules attempting to identify patients for early discharge based on a single troponin measurement have had varying success, highlighting the importance of serial troponin measurements to increase sensitivity [9], [10]. Recently, we reported that adding a second troponin measurement to the HEART score improved sensitivity for major adverse cardiac events from 58% to 100% in a low-risk cohort designated for observation unit care [9]. Therefore, the objective of this study was to determine the ability of three risk stratification strategies – an unstructured clinician assessment, NACPR, and HEART score, each combined with serial troponin measures – to identify patients for early discharge while maintaining an acceptable ACS miss rate (below 1%).
Section snippets
Study design
A secondary analysis was conducted of patients prospectively enrolled in the Myeloperoxidase In the Diagnosis of Acute coronary syndromes Study (MIDAS), clinical trial number NCT00415948. Participants were enrolled from May 2006 to September 2007, and all gave informed consent at the time of study entry. Details of the MIDAS trial have been previously described [11]. The MIDAS protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by
Results
From 12/2006 to 9/2007, 1107 patients with symptoms of suspected ACS were enrolled. Due to incomplete troponin data, 102 were excluded, leaving 1005 patients for analysis (Fig. 2). Complete assessment for 30 day ACS was obtained in 98% (988/1005) of the cohort, with their characteristics and outcomes summarized in Table 1. Most patients, 89.5% (899/1005), were admitted or received objective cardiac testing. Discharge from the ED without objective cardiac testing occurred in only 7.2% (72/1005)
Discussion
This analysis suggests that an unstructured assessment, NACPR, and HEART score, combined with 0 and 3 hour troponin measurements, can identify ED patients with acute chest pain for early discharge while retaining an acceptable ACS miss rate (below1%). These findings have added impact as these rules were applied to a cohort identified by their physicians as requiring objective cardiac testing. In fact, nearly 90% of this cohort were either admitted or received objective cardiac testing prior to
Conclusions
The HEART score combined with serial troponins identified a substantial number of patients for early discharge with a low missed ACS rate. Use of a structured clinical ACS risk assessment combined with two troponin results is highly sensitive for the detection of ACS. The HEART score plus serial troponins could improve efficiency and quality of chest pain care in the ED. A prospective study of the implementation of the HEART score and serial troponins is warranted.
Acknowledgment
The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.
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Funding: The MIDAS trial was funded by Biosite. In addition, Dr. Mahler receives funding from NIH T32 HL 87730.
Disclosures (past 12 months): Miller: research support from Siemens, 3M, PA Department of Health, American Heart Association, NIH. Provisional patent filing related to the prediction of coronary disease; Birkhahn: research support from Biosite, Alere, MediciNova, Astute Medical Inc., Bristol-Myers Squibb, NY Department of Health, NINDS; Nagurney: research support from Biosite, Alere, Clendevor, and NHLBI.
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This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.