5.4
Code 5.4 — Minnesota Code 5-4: low-amplitude positive T wave. The T wave is upright, but very small relative to the R wave: T amplitude less than 1/20 of the R amplitude in a lead where the R wave is at least 10 mm. It is the mildest T-wave item in the Minnesota Code and is classed as a minor abnormality. It is often non-specific, but in some cases it is an early marker of changed repolarisation.
Possible causes
- Low potassium, medicines (digoxin, antiarrhythmics, psychotropic drugs)
- Left ventricular hypertrophy, early ischaemic or post-ischaemic changes
- Hypothyroidism, anaemia, chronic lung disease
- Tachycardia, recent meal, hyperventilation
- Normal variant
Clinical significance
As a single finding, a low T wave has limited value. It becomes more relevant when it is new or combined with other ST-T changes, Q waves, high voltage or symptoms. In epidemiological research it is part of the group of minor ST-T abnormalities, which together are associated with a moderate increase in long-term cardiovascular risk.
Usually it is enough to discuss the result at a scheduled visit and to check blood pressure, cholesterol, glucose and, if appropriate, blood electrolytes. Seek urgent care if you have chest pain, breathlessness 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
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