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3.1

Minnesota Code 3-1: tall left-sided R waves (V5/V6 > 26 mm, limb leads > 20 mm, aVL > 12 mm) — the main ECG sign of left ventricular hypertrophy.

Code 3.1 — Minnesota Code 3-1: high-amplitude R waves (left). This code is assigned when the R wave is abnormally tall in the left-sided leads: R > 26 mm in V5 or V6, or R > 20 mm in any of I, II, III, aVF, or R > 12 mm in aVL. High R voltage is the main ECG criterion of left ventricular hypertrophy (LVH) — enlargement and thickening of the walls of the heart's main pumping chamber.

Minnesota Code 3High R voltageLeft ventricular hypertrophy

V5 / V6R > 26 mm

I, II, III, aVFR > 20 mm

aVLR > 12 mm

Sokolow–LyonS V1 + R V5/V6 ≥ 35 mm

What causes high R waves

A thickened left ventricular wall generates larger electrical forces, which are recorded as taller R waves in leads facing the left ventricle and deeper S waves in the right precordial leads. Left ventricular hypertrophy develops when the heart works against increased pressure or volume for a long time. It is initially an adaptation, but over time the thick, stiff muscle relaxes poorly, needs more oxygen and becomes prone to arrhythmias.

Figure 1. Left: normal R wave in V5. Middle: high R voltage (> 26 mm, Minnesota 3-1) with normal ST-T. Right: high R with ST depression and asymmetric T inversion — the 'strain' pattern of advanced LVH.

Main causes of left ventricular hypertrophy

Arterial hypertension — by far the most common cause
Aortic stenosis or regurgitation, mitral regurgitation
Hypertrophic cardiomyopathy (inherited thickening of the heart muscle)
Intensive endurance or strength training ("athlete's heart") — usually physiological and reversible
Infiltrative diseases (amyloidosis, Fabry disease), obesity, chronic kidney disease

Accuracy and interpretation

ECG voltage criteria are specific but not very sensitive: many people with LVH on echocardiography have normal voltage, while young, thin people and athletes may exceed the thresholds without hypertrophy. Combined criteria (Sokolow–Lyon, Cornell — R aVL + S V3 > 28 mm in men, > 20 mm in women) and the presence of ST-T "strain" changes increase reliability. ECG-detected LVH, especially with strain, is associated with increased risk of heart failure, atrial fibrillation, stroke and sudden death.

When to see a doctor

Discuss the finding with a doctor, especially if you have high blood pressure, a heart murmur, chest pain on exertion, breathlessness, fainting or a family history of cardiomyopathy or sudden death. Echocardiography confirms hypertrophy; blood-pressure control can make it regress.

References

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
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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