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5.1

Novacode 5.1: Q-wave myocardial infarction with major Q waves — how Novacode scores Q waves and what a prior infarction means.

Code 5.1 (Novacode NC-5.1) — Q-wave myocardial infarction with major Q waves. Novacode assigns this class when the ECG shows large, wide pathological Q waves in at least one lead group (anterior, inferior or lateral). This indicates that an area of heart muscle has been replaced by scar after a myocardial infarction (heart attack). The infarction may be recent or old, and sometimes it was "silent", without typical symptoms. The Minnesota equivalent is code 1-1-x.

Novacode 5Myocardial infarctionPathological Q waves

Novacode criterionQ-score ≥ 35 in a lead group

Minnesota equivalent1-1-x (major Q)

Typical Q≥ 40 ms or Q/R ≥ 1/3

Probability of MIhigh

How Novacode grades Q waves

Instead of the separate Minnesota categories, Novacode combines the duration and amplitude of Q waves in each lead group into a weighted Q-score, and ST and T changes into an ST-T score. Myocardial infarction is diagnosed from combinations of these scores. NC-5.1 to NC-5.4 together form the Novacode "ECG myocardial infarction" category; NC-5.1 is its most certain grade.

Novacode Q and ST-T classes as given in the classification table used by this application.
Class	Q-score / ST-T score	Meaning
NC-5.1	Q ≥ 35	Q-wave MI, high probability
NC-5.2	Q ≥ 25 and ST-T ≥ 20	Q-wave MI
NC-5.3	Q ≥ 25 and ST-T < 20	possible MI
NC-5.4	Q ≥ 15 and ST-T ≥ 20	possible MI
NC-5.5 / 5.6	Q < 15; ST or T score ≥ 20	isolated major ischaemia
NC-5.7 / 5.8	minor Q or minor ST-T	minor

Figure 1. Left: normal small septal q wave. Right: wide, deep pathological Q wave with reduced R wave and T inversion — the pattern of a Q-wave myocardial infarction.

Location of the infarction

Anterior (V1–V4): left anterior descending artery
Lateral (I, aVL, V5–V6): circumflex artery or diagonal branches
Inferior (II, III, aVF): right coronary artery or circumflex artery

Clinical significance

Major Q waves are a reliable sign of a previous myocardial infarction, which the Fourth Universal Definition calls "prior MI" when other causes are excluded. People with Q-wave infarction have a higher risk of heart failure, arrhythmias and new coronary events. Treatment aims to prevent further events (antiplatelet drugs, statins, blood-pressure and diabetes control, stopping smoking) and to protect heart function. Echocardiography shows the extent of scarring.

Call emergency services

if Q waves are new and you have chest pain, breathlessness, cold sweat or fainting — they may be a sign of an evolving infarction.

Planned evaluation

Even without symptoms, this finding needs a cardiology assessment, echocardiography and secondary prevention of coronary disease.

References

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.
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
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

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