BMJ  2007;335:623-624 (29 September), doi:10.1136/bmj.39339.380093.BE

Editorials

Effectiveness of chest pain units

Trial shows no benefit overall, but success may vary as a result of operational factors that are difficult to measure

Acute chest pain is responsible for one in four emergency medical admissions in the United Kingdom,¹ and these figures are probably similar in most Western countries. People with chest pain are rightly encouraged to seek help early, and attendances to emergency departments are rising. Emergency departments are responsible for quickly identifying and treating people with acute myocardial infarction and unstable angina, and for evaluating people with a lower likelihood of acute coronary syndrome.

Identifying which patients at low risk of acute coronary syndrome can be safely sent home and which patients need further observation and investigation is not easy, especially when the consequences of misdiagnosis include infarction, arrhythmia, and death. The strategy of evaluating such patients in a chest pain unit based within or near the emergency department is used in 30% of emergency departments in the United States.² The practice is supported by randomised trials that studied particular risk groups and methods of diagnosis, and in healthcare settings specific to the US, so the results may not be generaliseable elsewhere.^{3 4 5} In theory, a chest pain unit should improve outcomes—but does it?

In this week's BMJ, a cluster randomised controlled trial (effectiveness and safety of chest pain assessment to prevent emergency admissions; ESCAPE) by Goodacre and colleagues tries to answer this question.⁶ It follows on from the encouraging results of a previously reported single centre randomised trial, which found that a chest pain unit reduced hospital admissions and health service costs.⁷

The ESCAPE trial enrolled 14 hospitals, seven of which had a chest pain unit. The trial defined low risk patients as those with chest pain possibly as a result of acute coronary syndrome, but who had no new electrocardiographic changes diagnostic of the syndrome or prolonged or recurrent cardiac-type pain. In people admitted to hospitals with a chest pain unit, serial electrocardiography was performed over two to six hours, biochemical markers were measured, and an exercise treadmill test was typically performed the next working day. People admitted to hospitals without a chest pain unit received the usual service typically consisting of admission for troponin measurements over 12 hours, with no early exercise testing.⁸ The outcomes were measured the year before and the year after either the introduction of the chest pain unit or continuance of the same service. The introduction of a chest pain unit had no significant effect on the proportion of people attending the emergency department with chest pain, the proportion of people with chest pain who were admitted, or the number of people admitted over the next 30 days. However, a small increase was seen in the proportion of patients reattending (odds ratio 1.10, 95% confidence interval 1.00 to 1.21, P=0.036) and in the number of daily medical admissions (1.7 per day, 0.8 to 2.5, P<0.001).³

Setting up a chest pain unit led to more patients being tested, but no reduction in the proportion of patients admitted. Why was this? Perhaps different staffing levels and opening hours reduced the impact of the chest pain unit—this might partially explain the variation in the proportion of adult attendances managed in these units (1-7/1000 attendances at the emergency department). The variation in the average age, risk factors, and known coronary heart disease between the chest pain units suggests that some patient selection occurred.⁸ Why was there no effect overall even though some chest pain units worked well? Perhaps factors that determine the success of a service (such as enthusiasm of the staff, buy in by other relevant specialties) are difficult to measure in a trial setting. Clearly, one size does not fit all, and how these services fit within the wider context of health care is important.

Patients expect serious disease not to be missed, and unless hospitals are explicit about what risks they are prepared to accept and pay for, clinicians will use whatever tests and periods of observation they can to rule out serious disease. The failure of this trial to show a benefit of chest pain units does not reduce the need to find and implement a diagnostic strategy to discriminate in this growing low risk patient population between patients with a low likelihood of an adverse outcome related to the acute coronary syndrome—who can be safely discharged—and those who need further treatment or inpatient evaluation. Future studies need to focus on the successful implementation of a new diagnostic service and where possible how such testing can be simplified.

Emergency Department, Southampton General Hospital, Southampton SO31 9HS

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Competing interests: None declared.

Provenance and peer review: Commissioned; not externally peer reviewed.

References

1. Goodacre S, Cross E, Arnold J, Angelini K, Capewell S, Nicholl J. The health care burden of acute chest pain. Heart 2005;91:229-30.[Free Full Text]
2. Brady W, Harrigan R, Chan T. Acute coronary syndromes. In: Marx J, Hockberger R, Walls R, eds. Rosen's emergency medicine. Concepts and clinical practice. 6th ed. Edinburgh: Mosby Elsevier, 2006:1154-99.
3. Farkouh ME, Smars PA, Reeder GS, Zinsmeister AR, Evans RW, Meloy TD, et al. A clinical trial of chest-pain observation unit for patients with unstable angina. N Engl J Med 1998;339:1882-8.[Abstract/Free Full Text]
4. Roberts RR, Zalenski RJ, Mensah EK, Rydman RJ, Ciavarella G, Gussow L, et al. Costs of an emergency department based accelerated diagnostic protocol vs hospitalization in patients with chest pain. A randomised controlled trial. JAMA 1997;278:1670-6.[Abstract]
5. Gomez MA, Anderson JL, Karagounis LA, Muhlestein JB, Mooers FB. An emergency department based protocol for rapidly ruling out myocardial ischemia reduces hospital time and expense: results of a randomised study (ROMIO). J Am Coll Cardiol 1996;28:25-33.[Abstract]
6. Goodacre S, Cross E, Lewis C, Nicholl J, Capewell S; on behalf of the ESCAPE Research Team. Effectiveness and safety of chest pain assessment to prevent emergency admissions: ESCAPE cluster randomised trial. BMJ 2007 doi: 10.1136/bmj.39325.624109.AE[Abstract/Free Full Text]
7. Goodacre S, Nicholl J, Dixon S, Cross E, Angelini K, Arnold J, et al. Randomised controlled trial and economic evaluation of a chest pain observation unit compared with routine care. BMJ 2004;328:254-7.[Abstract/Free Full Text]
8. Arnold J, Goodacre S, Morris F; ESCAPE Research Team. Structure, process and outcomes of chest pain units established in the ESCAPE trial. Emerg Med J 2007;24:462-6.[Abstract/Free Full Text]

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