1.12
Code 1.12 — Minnesota Code 1-1-2: major Q/QS wave by duration. This code is assigned when the Q wave is 0.04 s (40 ms) or wider in the leads of one anatomical region, regardless of its depth relative to the R wave. A Q wave of this width is rarely a normal septal q and is a major electrocardiographic sign of a previous myocardial infarction.
What the code means
The duration of a Q wave reflects how long the electrical activation is directed away from the recording electrode. In healthy hearts septal q waves are short — usually less than 0.03 s. A Q wave lasting 40 ms or more means that a substantial part of the wall under the electrode does not generate electrical forces, typically because it has been replaced by scar after myocardial infarction. The universal definition of myocardial infarction also uses Q-wave duration (≥ 0.03–0.04 s in two contiguous leads) as an ECG criterion of prior infarction.
Criteria by lead group
| Region | Leads examined | Code 1-1-2 criterion |
|---|---|---|
| Anterolateral | I, aVL, V6 | Q duration ≥ 0.04 s in lead I or V6 |
| Posterior (inferior) | II, III, aVF | Q duration ≥ 0.04 s in lead II |
| Anterior | V1–V5 | Q duration ≥ 0.04 s in any of V1–V5 |
Clinical significance
Wide Q waves point to transmural or extensive scar. Their location helps to identify the affected coronary territory: anterior leads — left anterior descending artery; inferior leads — usually the right coronary artery; lateral leads — the circumflex or diagonal branches. People with such Q waves have a higher risk of heart failure, ventricular arrhythmias and cardiovascular death and benefit from secondary prevention.
Other possible causes
- Hypertrophic or dilated cardiomyopathy
- Left bundle branch block, marked left ventricular hypertrophy
- Infiltrative diseases, myocarditis, cardiac tumours
- Electrode misplacement, especially of the precordial leads
Recommended next steps
- Compare with older ECGs to date the finding
- Echocardiography or cardiac MRI to confirm scar and assess heart function
- Control of cardiovascular risk factors; cardiology follow-up
if the Q wave is new and accompanied by chest pain, shortness of breath, sweating or fainting.
References
- 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
- 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
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