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3.3

Minnesota Code 3-3: borderline left R voltage (lead I R 15–20 mm or R V5/V6 + S V1 > 35 mm) — a grey-zone finding between normal and LVH.

Code 3.3 — Minnesota Code 3-3: borderline high-amplitude R waves (left). This code marks R-wave voltage that is increased, but below the threshold of code 3-1: R wave over 15 mm and up to 20 mm in lead I, or R in V5 or V6 plus S in V1 over 35 mm. It is a "grey-zone" finding: it may be an early sign of left ventricular hypertrophy, but it is also common in young, slim people and athletes.

Minnesota Code 3Borderline R voltageLeft ventricle

Lead IR > 15 and ≤ 20 mm

Precordial sumR V5/V6 + S V1 > 35 mm

Higher classcode 3-1 (R V5/V6 > 26 mm)

Confirmationechocardiography

What it means

QRS voltage depends not only on the mass of the left ventricle but also on the distance between the heart and the electrodes, chest-wall thickness, lung tissue and body build. That is why the same voltage may reflect hypertrophy in one person and a normal, thin chest wall in another. The criterion R V5/V6 + S V1 > 35 mm corresponds to the classic Sokolow–Lyon index.

Figure 1. Gradation of left-sided R voltage: normal, borderline (Minnesota 3-3) and high (Minnesota 3-1). The ST-T segment is normal in the borderline pattern.

Who has this pattern

Often normal

Age under 35–40, slim body build, regular sports training, no high blood pressure, normal ST-T.

Possible hypertrophy

Arterial hypertension, aortic stenosis, heart murmur, ST-T changes, left atrial enlargement, increase on serial ECGs.

Clinical significance

On its own, code 3-3 is a minor finding. In epidemiological studies it is used to track the development of hypertrophy over time; an increase in voltage on repeated ECGs is more informative than one value. In people with high blood pressure the finding is a reason to check blood pressure control and to consider echocardiography.

What to do

Measure your blood pressure regularly. Tell your doctor if you have exertional chest pain, breathlessness, fainting or a family history of cardiomyopathy — in that case echocardiography is advisable.

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
Hancock EW, Deal BJ, Mirvis DM, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part V: electrocardiogram changes associated with cardiac chamber hypertrophy. Circulation. 2009;119(10):e251–e261. doi:10.1161/CIRCULATIONAHA.108.191097
Sokolow M, Lyon TP. The ventricular complex in left ventricular hypertrophy as obtained by unipolar precordial and limb leads. Am Heart J. 1949;37(2):161–186. doi:10.1016/0002-8703(49)90562-1

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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