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    5.4
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    5.4

    Novacode 5.4: possible myocardial infarction with minor Q waves and ST-T changes — interpretation and next steps.

    Code 5.4 (Novacode NC-5.4) — possible Q-wave myocardial infarction: minor Q waves with ST-T changes. The Q waves are small (minor), but they are accompanied by significant ST-segment or T-wave abnormalities. Together these changes suggest a possible past myocardial infarction or ischaemic damage. This is the least certain class of Novacode ECG myocardial infarction. The approximate Minnesota equivalent is 1-3-x combined with 4-1/4-2 or 5-1/5-2.

    Novacode 5Possible myocardial infarctionMinor Q + ST-T
    Novacode criterionQ-score ≥ 15 and ST-T ≥ 20
    Minnesota equivalent1-3-x + 4-1/4-2 or 5-1/5-2
    Typical Q20–30 ms
    Probability of MIpossible
    Normal complex compared with a small Q wave accompanied by ST depression and T wave inversion Normal q < 20 ms NC-5.4 minor Q + ST-T
    Figure 1. Left: normal complex. Right: small (minor) Q wave with ST depression and T-wave inversion — Novacode class 5.4.

    Interpretation

    Minor Q waves alone are common and usually harmless. What raises suspicion here are the ST-T changes in the same region, which may indicate ischaemia or a small, non-transmural scar. However, ST-T changes can also be caused by hypertrophy, medicines or electrolyte disorders, so the class is labelled only "possible" infarction.

    Clinical significance

    This finding calls for a cardiology assessment: comparison with earlier ECGs, echocardiography and, depending on symptoms and risk factors, a stress test or coronary imaging. Risk factors for coronary disease (blood pressure, cholesterol, diabetes, smoking) should be treated actively.

    Call emergency services

    if you have chest pain, pressure, breathlessness, cold sweat or fainting.

    References

    1. Rautaharju PM, Park LP, Chaitman BR, Rautaharju F, Zhang ZM. The Novacode criteria for classification of ECG abnormalities and their clinically significant progression and regression. J Electrocardiol. 1998;31(3):157–187.
    2. Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018). Eur Heart J. 2019;40(3):237–269. doi:10.1093/eurheartj/ehy462
    3. Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3

    This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.

    Published on 14 May 2019