A Clinical Prediction Rule for Early Discharge of Patients With Chest Pain

doi:10.1016/j.annemergmed.2005.08.007

Annals of Emergency Medicine

Volume 47, Issue 1, January 2006, Pages 1-10

https://doi.org/10.1016/j.annemergmed.2005.08.007 Get rights and content

Study objective

Current risk stratification tools do not identify very-low-risk patients who can be safely discharged without prolonged emergency department (ED) observation, expensive rule-out protocols, or provocative testing. We seek to develop a clinical prediction rule applicable within 2 hours of ED arrival that would miss fewer than 2% of acute coronary syndrome patients and allow discharge within 2 to 3 hours for at least 30% of patients without acute coronary syndrome.

Methods

This prospective, cohort study enrolled consenting eligible subjects at least 25 years old at a single site. At 30 days, investigators assigned a diagnosis of acute coronary syndrome or no acute coronary syndrome according to predefined explicit definitions. A recursive partitioning model included risk factors, pain characteristics, physical and ECG findings, and cardiac marker results.

Results

Of 769 patients studied, 77 (10.0%) had acute myocardial infarction and 88 (11.4%) definite unstable angina. We derived a clinical prediction rule that was 98.8% sensitive and 32.5% specific. Patients have very low risk of acute coronary syndrome if they have a normal initial ECG, no previous ischemic chest pain, and age younger than 40 years. In addition, patients at least 40 years old and with a normal ECG result, no previous ischemic chest pain, and low-risk pain characteristics have very low risk if they have an initial creatine kinase-MB (CK-MB) less than 3.0 μg/L or an initial CK-MB greater than or equal to 3.0 μg/L but no ECG or serum-marker increase at 2 hours.

Conclusion

The Vancouver Chest Pain Rule for early discharge defines a group of patients who can be safely discharged after a brief evaluation in the ED. Prospective validation is needed.

Introduction

Approximately 15% to 25% of patients who present to emergency departments (EDs) with undifferentiated chest pain prove to have acute coronary syndrome within 30 days. US data suggest that 2.1% of patients with acute myocardial infarction and 2.3% of patients with unstable angina are initially misdiagnosed,¹ whereas a recent Canadian study identified 11 of 241 (4.6%) missed cases of acute myocardial infarction and 10 of 157 (6.4%) cases of missed unstable angina.² Chest pain units reduce the rate of missed myocardial infarction but do so in part by including very-low-risk patients in extensive rule-out myocardial infarction protocols.3, 4, 5

Many investigators have developed chest pain risk stratification tools. Goldman et al⁶ developed a clinical/ECG algorithm that identified patients with less than 7% risk of acute myocardial infarction. Limkakeng et al⁷ subsequently found that 4.9% of patients who had low-risk Goldman criteria and a negative initial troponin I assay result experienced death, acute myocardial infarction, or revascularization within 30 days. Pozen et al8, 9 developed a 7-item predictive equation that reduced coronary care unit admissions but not inappropriate discharges. Selker et al10, 11, 12 modified this to create the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI), which defined low risk as less than 10% chance of acute coronary syndrome. The Erlanger protocol¹³ is an intense 2-hour assessment that includes serial ECGs and creatine kinase-MB (CK-MB) and troponin measurements, but it does not define a subset of patients who can forgo nuclear stress testing. The American Heart Association/Agency for Health Care Policy and Research guidelines suggest early discharge only for patients with “evidence” of an alternate diagnosis.¹⁴ Unfortunately, few patients clearly fall into this category. Our own study of patients with chest pain at 2 Vancouver hospitals identified that 5.4% of patients with acute coronary syndrome were discharged from the ED without a diagnosis or planned investigations and only 30% of those without acute coronary syndrome were discharged less than three hours after ED admission.²

Clinical prediction rules are decisionmaking tools for clinicians that contain elements of the medical history, physical examination, and simple diagnostic tests.¹⁵ An objective clinical prediction rule to identify very-low-risk patients with chest pain who can be safely discharged without prolonged ED observation, expensive rule-out protocols, or provocative testing is needed. Such a rule would help reduce emergency crowding, minimize patient inconvenience, and improve cost-effectiveness of acute coronary syndrome diagnostic testing.

Our specific objective was to develop a clinical prediction rule that would improve on current practice by identifying patients with chest pain who are safe for discharge after 2 hours of ED evaluation. The rule will miss fewer than 2% of acute coronary syndrome patients and allow discharge within 2 to 3 hours of at least 30% of patients without acute coronary syndrome.

Section snippets

Study Design

Using established methodology for clinical prediction rules,15, 16, 17 this prospective cohort study was conducted in 2 separate periods between June 29, 2000, and January 24, 2003, when research assistants were funded.

Setting and Selection of Participants

Patients presenting to St. Paul's Hospital, an urban tertiary care ED, with a primary complaint of anterior or lateral chest pain were eligible for the study. Research assistants obtained informed consent and enrolled eligible patients between 7 am and 10 pm 7 days per week.

Results

We enrolled 819 patients and subsequently excluded 50 patients from analysis, 31 who met exclusion criteria and 19 who were lost to follow-up. Of the 19 lost to follow-up, 14 were known to be alive at subsequent hospital visits, and the other 5 did not appear in the provincial death registry. Table 1 summarizes baseline characteristics and outcomes for the 769 patients analyzed showing 30-day diagnosis was acute myocardial infarction in 77 (10.0%) and definite unstable angina in 88 (11.4%).

Limitations

Although we used accepted and validated methodology,¹⁵ the Vancouver Chest Pain Prediction Rule was developed in 1 cohort of patients in a single center. We are currently beginning validation of the rule, and it will subsequently require evaluation of implementation in multiple centers. Our criterion standard for definite acute coronary syndrome was not based on mandated investigations but on a careful evaluation of all tests and visits during 30 days. It is possible that we missed some

Discussion

Patients who present to the ED with chest pain fall into 3 categories: those with objective ischemia who need admission and treatment, those with a clear noncardiac cause, and those who require a diagnostic process to rule out acute coronary syndrome and other life-threatening conditions. The Vancouver Chest Pain Rule identifies 32.5% of patients who do not have acute coronary syndrome using information available in the first 2 hours of the ED visit. These very-low-risk patients are identified

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The ideal high-sensitivity troponin (hsTn) cutoff for identifying those at low risk of 30 days events is debated; however, the 99th percentile overall or gender-specific upper reference limit (URL) is most commonly used. The magnitude of risk and the best management strategy for those with low-level hsTn elevation hasn’t been extensively studied.
We conducted a retrospective cohort analysis including 4396 chest pain patients (542 with low-level hsTn elevation) who ruled out for myocardial infarction (MI), had a stable high-sensitivity troponin T (hsTnT) levels (defined as < 5 ng/l inter-measurements increase in hsTnT levels), and were discharged from the emergency department without further ischemic testing. The aim of the study was to compare the 30-day incidence of adverse cardiac events (ACE) between patients with undetectable high-sensitivity troponin T (hsTnT) (group 1), patients with hsTnT within the 99th percentile sex-specific URL (group 2), and patients with low-level hsTnT elevation (between the 99th percentile URL and ≤ 50 ng/l) (group 3).
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Supervising editor: Judd E. Hollander, MD

Author contributions: DM, HR, EY, EG, FR, AA, and JS helped design the study, analyzed the data, and reviewed the manuscript. BB helped design the study, collected data, and reviewed the manuscript. JMC, GI, and CRT conceived and helped design the study, collected data, and wrote the manuscript. JMC takes responsibility for the paper as a whole.

Funding and support: Canadian Institutes of Health research grant MOP 53102 and Heart and Stroke Foundation of British Columbia and Yukon Grant. Materials for analysis of some laboratory testing were donated by Biosite.

Reprints not available from the authors.

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Original ResearchA Clinical Prediction Rule for Early Discharge of Patients With Chest Pain

Study objective

Methods

Results

Conclusion

Introduction

Section snippets

Study Design

Setting and Selection of Participants

Results

Limitations

Discussion

Am J Cardiol

Am J Cardiol

J Electrocardiol

Ann Emerg Med

Ann Emerg Med

Am J Med

Ann Emerg Med

Ann Emerg Med

Lancet

Am J Cardiol

Ann Emerg Med

Missed diagnoses of acute cardiac ischemia in the emergency department

N Engl J Med

Safety and efficiency of emergency department assessment of chest discomfort

CMAJ

Hospitals battle heart attacks with new chest pain centers

Hospitals

A computer protocol to predict myocardial infarction in emergency department patients with chest pain

N Engl J Med

Combination of Goldman risk and initial cardiac troponin I for emergency department chest pain patient risk stratification

Acad Emerg Med

Original Research
A Clinical Prediction Rule for Early Discharge of Patients With Chest Pain