# U wave mimicking long QT interval: the role of lead selection, repeated electrocardiograms, and premature atrial complexes

Fawzi Kerkouri, Florent Le Ven, Sarah Kerkouri, Jacques Mansourati

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Fawzi Kerkouri, Florent Le Ven, Sarah Kerkouri, Jacques Mansourati. U wave mimicking long QT interval: the role of lead selection, repeated electrocardiograms, and premature atrial complexes. European Heart Journal. Case Reports, 2025, 9 (6), pp.ytaf264. 10.1093/ehjcr/ytaf264. hal-05219698

HAL Id: hal-05219698

https://hal.univ-brest.fr/hal-05219698v1

Submitted on 22 Aug 2025

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Distributed under a Creative Commons Attribution 4.0 International License
# U wave mimicking long QT interval: the role of lead selection, repeated electrocardiograms, and premature atrial complexes

Fawzi Kerkouri ID ¹,²*, Florent Le Ven¹, Sarah Kerkouri³, and Jacques Mansourati¹,²

¹Department of Cardiology, University Hospital of Brest, Boulevard Tanguy Prigent, 29200 Brest, France; ²Université de Bretagne Occidentale (Univ Brest), Inserm, ORPHY EA 4324, 29200 Brest, France; and ³Université de Bretagne Occidentale (Univ Brest), CHU de Brest, 29200 Brest, France

Received 9 December 2024; revised 6 March 2025; accepted 19 May 2025; online publish-ahead-of-print 27 May 2025

**ESC curriculum** 5.6 Ventricular arrhythmia • 5.8 Cardiac ion channel dysfunction

## Case presentation

A 78-year-old woman with hypertension, paroxysmal atrial fibrillation treated by amiodarone (200 mg/day), and idiopathic pulmonary hypertension was admitted for cardiac decompensation. Her baseline electrocardiogram (ECG) showed sinus dysfunction and an apparently prolonged corrected QT (QTc) interval (540 ms) in leads V5 and DII (Figure 1A), without electrolyte disturbances or ischaemia. To determine if this represented true QT prolongation or false prolongation due to U-T wave fusion,¹ repeated ECGs at varying heart rates were performed. At 54/min, a double wave appeared in V5, suggesting a possible

U wave causing false QT prolongation (Figure 1B). At 58/min, the second wave amplitude exceeded the first and notably decreased following premature atrial complexes (PACs). This cycle length variation supports its identification as a U wave rather than a bifid T wave (Figure 1C).² At 62/min after mild exercise, the second wave amplitude further diminished, particularly after PACs, reinforcing its identification as a U wave (Figure 1D). As recommended leads (V5/II) showed persistent U-T wave fusion,³ measuring QT interval in these leads would erroneously suggest QT prolongation. Therefore, QT interval was accurately assessed in lead V2, where T and U waves were clearly separated, confirming a normal QT interval of 400 ms.

<footnote>* Corresponding author. Tel: +33 7 67 14 95 58, Email: eecmcfawzikerkouri@gmail.com</footnote>

<footnote>Handling Editor: Bogdan Enache</footnote>

<footnote>Peer-reviewers: Sebastian Feickert; Boldizsar Kovacs; Vera Maslova; Fabian Barbieri</footnote>

<footnote>© The Author(s) 2025. Published by Oxford University Press on behalf of the European Society of Cardiology.</footnote>

<footnote>This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.</footnote>
<figure><img src="image_2.png" /><figcaption>**Figure 1** (A) Baseline ECG at 47/min showing prolonged QT interval in DII/V5. (B) At 54/min, a double wave appeared in V5, suggesting potential U wave fusion. (C) At 58/min, the second wave's amplitude varied with heart rate and premature atrial complexes, while the T wave remained unchanged, supporting its identification as a U wave. (D) At 62/min, the second wave amplitude decreased, further reduced by premature atrial complexes, confirming the U wave's sensitivity to cycle length. QT interval was measured in V2, where T and U waves were clearly separated.</figcaption></figure>

**Acknowledgements**

The authors would like to thank the patient for consenting to share this case report.

**Consent:** The authors confirm that written consent for submission and publication of this case report, including images and associated text, has been obtained from the patient in line with COPE guidance.

*Conflict of interest:* None declared.

**Funding:** No funding.

**Data availability**

The data supporting the findings of this case report are available from the corresponding author upon reasonable request.

**References**

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2. Postema PG, Wilde AAM. The measurement of the QT interval. *Curr Cardiol Rev* 2014; **10**:287–294.

3. Tisdale JE, Chung MK, Campbell KB, Hammadah M, Joglar JA, Leclerc J, et al. Drug-induced arrhythmias: a scientific statement from the American Heart Association. *Circulation* 2020;**142**:e214–e233.