Letters

Diagnosing myocardial infarction

BMJ 2001; 323 doi: https://doi.org/10.1136/bmj.323.7325.1366 (Published 08 December 2001) Cite this as: BMJ 2001;323:1366

Randomised controlled trial and economic evaluation of a chest pain unit are in progress

  1. Steve Goodacre, health services research fellow (s.goodacre{at}sheffield.ac.uk),
  2. Francis Morris, consultant in accident and emergency medicine,
  3. Stephen Campbell, consultant cardiologist,
  4. Deborah Quinney, research fellow,
  5. Simon Capewell, chair of clinical epidemiology
  1. Medical Care Research Unit, University of Sheffield, Sheffield S1 4DA
  2. Northern General Hospital, Sheffield S5 7AU
  3. Department of Public Health, University of Liverpool, Liverpool L69 3BG
  4. Chest Pain Evaluation Unit, St Joseph Mercy Hospital, Pontiac, MI 48321, USA

    EDITOR—Acute chest pain is an important, but neglected, problem in the United Kingdom.1 Emerging diagnostic approaches, such as the use of ST segment monitoring in emergency departments, new cardiac markers, and chest pain units have been extensively investigated in the United States.2-4 Yet evaluation in the United Kingdom has progressed little beyond audit. Herren et al should therefore be congratulated for embarking on rigorous evaluation of this problem.5 The protocol they describe has impressive diagnostic performance for myocardial infarction. There are, however, several reasons why we cannot assume that this will lead to improved patient care and cost effectiveness.

    Assessment of acute chest pain requires more than simply ruling out myocardial infarction. Chest pain units in the United States typically provide provocative cardiac testing to stratify their patients further by risk. Immediate exercise stress testing is feasible in British emergency departments and is provided to patients within six hours of attendance at the Northern General Hospital in Sheffield.

    The Manchester study enrolled 383 patients over the course of one year. This represents approximately one patient per day and accounts for only a small proportion of attendances with chest pain to an urban emergency department. In these circumstances the selection process may be as important as the diagnostic protocol itself. A substantial proportion of patients have known coronary heart disease and present with characteristic angina-type pain, but have no diagnostic changes on electrocardiography. Were these patients included in the study? If not, how were they excluded?

    Without a control group it is impossible to know how the cohort described would be managed if there were no chest pain unit. American studies of chest pain units have shown cost savings compared with a control group that is routinely admitted and shown improved effectiveness compared with control groups with substantial discharge rates.4 A meaningful comparison should, however, reflect current routine practice—patients admitted or discharged according to the clinicians' judgment.

    A randomised controlled trial incorporating such a control group is currently in progress at the Northern General Hospital in Sheffield. An identical gold standard to that used in Manchester (troponin T) is being used to compare diagnostic accuracy. Evaluation also includes cardiac events over six months, quality of life, health utility, patient satisfaction, and cost effectiveness. Until such data are available chest pain units should be considered to be of unproved value in the United Kingdom.

    References

    1. 1.
    2. 2.
    3. 3.
    4. 4.
    5. 5.

    Additional tools may help to identify patients at low risk

    1. Carl E Palffy, director (palfmd{at}aol.com)
    1. Medical Care Research Unit, University of Sheffield, Sheffield S1 4DA
    2. Northern General Hospital, Sheffield S5 7AU
    3. Department of Public Health, University of Liverpool, Liverpool L69 3BG
    4. Chest Pain Evaluation Unit, St Joseph Mercy Hospital, Pontiac, MI 48321, USA

      EDITOR—The major flaw of the article by Herren et al is that it proposes that ruling out myocardial infarction allows a doctor to assume that the patient is at low risk and may be discharged from the emergency centre.1 Perhaps these patients are at low risk of myocardial infarction but not coronary artery disease. Another study, using a stress test or minimally invasive angiography, could elucidate this point.

      In our unit we typically use a period of 9–12 hours of serial cardiac enzyme measurements (CPK-mb or troponin i), in conjunction with ST segment monitoring, to rule out patients with myocardial infarction. The patient then has a stress thallium test or, at the preference of the cardiologist, heart catheterisation or coronary angiography. After a negative result on testing for ischaemia, the patient can then be safely discharged. It would be interesting to see if a six hour period of observation could be substituted for our current 9–12 hours. But to assert confidently that a patient is at low risk of coronary disease and poor outcome, this study would have to include a larger patient population, the gold standard of coronary imaging, and careful follow up of patients for adverse outcomes.

      References

      1. 1.
      View Abstract

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