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Multi-beat averaging reveals u waves are ubiquitous and standing tall at elevated heart rates following exercise

Al-Karadi, Marwa S.; Langley, Philip


Marwa S. Al-Karadi


The reporting of U wave abnormalities is clinically important, but the measurement of this small electrocardiographic (ECG) feature is extremely difficult, especially in challenging recording conditions, such as stress exercise, due to contaminating noise. Furthermore, it is widely stated that ECG U waves are rarely observable at heart rates greater than 90 bpm. The aims of the study were (i) to assess the ability of multi-beat averaging to reveal the presence of U waves in ECGs contaminated by noise following exercise and (ii) to quantify the effect of exercise on U wave amplitude. The multi-beat averaging algorithm was applied to recover U waves in 20 healthy subjects in pre- and post-exercise recordings. Average beats were generated from 30 beat epochs. The prevalence of U waves and their amplitudes were measured in pre- and post-exercise recordings and changes in amplitude due to exercise were quantified. U waves were present in all subjects in pre-exercise recordings. Following exercise, U waves could not be seen in standard ECG but were observable in all 20 subjects by multi-beat averaging and despite significantly increased mean (±SD) heart rate (63 ± 8 bpm vs. 100 ± 9 bpm, p < 0.0001). Furthermore, U waves were observable in all subjects with heart rates greater than 90 bpm. U waves significantly increased in amplitude following exercise (38 ± 15 μV vs. 80 ± 48 μV, p = 0.0005). Multi-beat averaging is effective at recovering U waves contaminated by noise due to exercise. U waves were measurable in all subjects, dispelling the myth that U waves are rarely seen at elevated heart rates. U waves exhibit increased amplitudes at elevated heart rates following exercise.


Al-Karadi, M. S., & Langley, P. (2020). Multi-beat averaging reveals u waves are ubiquitous and standing tall at elevated heart rates following exercise. Sensors, 20(14), 1-12.

Journal Article Type Letter
Acceptance Date Jul 18, 2020
Online Publication Date Jul 20, 2020
Publication Date Jul 2, 2020
Deposit Date Jul 25, 2020
Publicly Available Date Oct 27, 2022
Journal Sensors (Switzerland)
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 20
Issue 14
Article Number 4029
Pages 1-12
Keywords ECG U wave; ECG T wave; Multi-beat averaging algorithm; Exercise ECG; High heart rates
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Copyright Statement
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (

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