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• New definition of an abnormal Q wave – is it clinically useful?
  Jesper Khédri Jensen
  Published on: 14 November 2005

• Published on: 14 November 2005

  New definition of an abnormal Q wave – is it clinically useful?

  • Jesper Khédri Jensen, MD
  • Other Contributors:
    • Hans Mickley, Poul Flemming Hoilund-Carlsen

  Dear Editor

  Since myocardial infarction (MI) was redefined five years ago(1), focus has been on troponins. However, with the consensus document the presence of an abnormal Q wave has also been redefined, but this change appears to have created only little controversy. Abnormal Q waves are still considered a definite objective sign of an established MI, and in this connection, the history of the patient is often in...

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  Dear Editor

  Since myocardial infarction (MI) was redefined five years ago(1), focus has been on troponins. However, with the consensus document the presence of an abnormal Q wave has also been redefined, but this change appears to have created only little controversy. Abnormal Q waves are still considered a definite objective sign of an established MI, and in this connection, the history of the patient is often insufficient(2). For decades the Minnesota criteria in different editions have been used worldwide, but a set of generally accepted international electrocardiographic criteria for an established MI have so far not been available. Therefore, we welcome the joint European-American initiative(1).

  However, using the new definition of an abnormal Q wave we recently demonstrated an increase in the proportion of patients categorized as having an established MI(3). This observation may result in additional patient examinations and a change in outcome measures of clinical and epidemiological trials. Finally, the redefinition may have consequences of psycho-social importance to the individual patient. Of interest, the new definition of an abnormal Q wave has been interpreted differently in recent Danish guidelines and in the series "Education in Heart"(4, 5). This, of course, is not appropriate and may cause confusion. A definition should be unambiguous.

  There exist no generally accepted set of rules defining how small the rate of false positive and false negative diagnoses should be in order to be "acceptable". This decision should preferably be based on a careful clinical judgement. In the present case, we propose that the false positive rate should be equal to the false negative rate and be <10- 15%.

  Finally, cardiologists and other physicians treating patients with ischemic heart disease should be familiar with the new Q wave definition (Table 1)1 in order to cope with the clinical dilemmas it may give rise to.

  Table 1 Electrocardiographic changes in established MI

  1. Any QR wave in leads V1 through V3 ≥ 30 ms (0.03 s);
  abnormal Q wave in lead I, II, aVL, aVF or V4 through
  V6 in any two contiguous leads and at least 1 mm in depth.

  References

  1. Myocardial infarction redefined--a consensus document of the joint european society of cardiology/american college of cardiology committee for the redefinition of myocardial infarction. Eur Heart J. 2000;21:1502- 1513

  2. Ammar KA, Kors JA, Yawn BP, Rodeheffer RJ. Defining unrecognized myocardial infarction: A call for standardized electrocardiographic diagnostic criteria. Am Heart J. 2004;148:277-284

  3. Jensen JK, Ovrehus K, Moldrup M, Mickley H, Hoilund-Carlsen PF. Redefinition of the Q wave - is there a clinical problem? Am J Cardiol. 2005:Accepted

  4. Grande P, Holmvang L. Akut koronart syndrom. Dansk Cardiologisk Selskab. 2004

  5. French JK, White HD. Clinical implications of the new definition of myocardial infarction. Heart. 2004;90:99-106

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  Conflict of Interest:
  None declared.

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