4.12

Minnesota Code 4-1-2: horizontal or down-sloping ST depression 1–2 mm — causes, ischaemia and next steps.

Code 4.12 — Minnesota Code 4-1-2: moderate ST depression. The J point is depressed by 1.0 mm or more but less than 2.0 mm below the PR baseline, with a horizontal or down-sloping ST segment. Like code 4-1-1, it belongs to the major ST abnormalities of the Minnesota Code. It typically indicates myocardial ischaemia or other repolarisation disturbances that need medical evaluation.

Minnesota Code 4ST depressionMyocardial ischaemia

ST-J depression1.0 – < 2.0 mm

ST shapehorizontal or down-sloping

Classmajor abnormality

Exercise test≥ 1 mm = positive

What it means

When part of the heart muscle receives too little blood, mainly the inner layer (subendocardium) is affected, and the surface ECG records ST depression in leads facing that area. A depression of 1 mm with a horizontal or down-sloping course is also the classic criterion of a positive exercise stress test. On a resting ECG, it may reflect ongoing ischaemia, hypertrophy with strain, the effect of drugs or electrolyte disturbances.

Figure 1. Left: normal ST segment. Right: horizontal ST-J depression of about 1.5 mm (Minnesota 4-1-2) with a flattened T wave.

Interpretation depends on context

Other explanations

Left ventricular hypertrophy (with high R voltage), digoxin, low potassium, fast heart rate, hyperventilation, bundle branch block (in which ST changes are not coded).

Suggests ischaemia

Chest pain or breathlessness on exertion, risk factors (smoking, diabetes, hypertension, high cholesterol), new changes compared with a previous ECG, changes in several neighbouring leads.

Clinical significance

In population cohorts, ST depression on the resting ECG has been associated with a higher risk of coronary events and death, independent of traditional risk factors. When a cause is not obvious, further evaluation usually includes echocardiography and a stress test or coronary imaging.

Call emergency services

if ST depression appears together with chest pain, pressure or tightness, breathlessness, cold sweat 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
Rautaharju PM, Surawicz B, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval. Circulation. 2009;119(10):e241–e250. doi:10.1161/CIRCULATIONAHA.108.191096
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

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