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    5.3
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    5.3

    Novacode 5.3: possible myocardial infarction with moderate Q waves and no major ST-T changes — other causes and confirmation.

    Code 5.3 (Novacode NC-5.3) — possible Q-wave myocardial infarction: moderate Q waves without major ST-T changes. The ECG shows moderate pathological Q waves, but the ST segment and T waves are normal or only slightly changed. A past myocardial infarction is possible, but less certain than in classes NC-5.1 and NC-5.2. The approximate Minnesota equivalent is code 1-2-x.

    Novacode 5Possible myocardial infarctionModerate Q waves
    Novacode criterionQ-score ≥ 25 and ST-T < 20
    Minnesota equivalent1-2-x
    ST-Tno major changes
    Probability of MImoderate / possible
    Normal complex compared with a moderate Q wave and normal ST segment and T wave Normal q < 30 ms NC-5.3 moderate Q, ST-T normal
    Figure 1. Left: normal complex. Right: moderate Q wave (about 30–40 ms) with a normal ST segment and upright T wave — Novacode class 5.3.

    Other causes of moderate Q waves

    • Old myocardial infarction with good healing
    • Hypertrophic cardiomyopathy (deep, narrow "septal" Q waves)
    • Left ventricular hypertrophy, left bundle branch block, WPW pattern
    • Chronic lung disease, heart position, lead misplacement
    • Normal variant, especially an isolated Q in lead III or aVL

    Clinical significance

    Because the probability of infarction is moderate, the finding is usually checked with echocardiography: a wall-motion abnormality in the matching region supports a past infarction. Previous ECGs help to establish whether the Q waves are new. Regardless of the final diagnosis, coronary risk factors should be assessed.

    What to do

    Arrange a visit with a doctor or cardiologist and bring previous ECGs. Seek urgent care if you have chest pain, breathlessness 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