Monitoring of cardiorespiratory vagal desynchrony using novel biomarkers derived from smartwatch electrocardiograms in a patient recovering from long COVID : case report
Kranck, Gustaf ; Ståhlberg, Marcus ; Andersson, Ulf ; Lundin, Johan and Fedorowski, Artur LU
(2025)
In European Heart Journal - Case Reports
9(10).
- Abstract
BACKGROUND: Long COVID and cardiovascular autonomic dysfunction, including postural orthostatic tachycardia syndrome (POTS), present significant healthcare challenges. Long-term monitoring is challenging due to the evolving nature of symptoms and the limited availability of objective diagnostic tools. With over 200 million electrocardiogram (ECG)-enabled smartwatches sold worldwide, these devices offer a promising solution for at-home diagnostics and disease tracking.
METHODS AND RESULTS: This study examines a 35-year-old male with long COVID, POTS, and chronic fatigue syndrome (CFS), who recorded 328 ECGs over using a Samsung smartwatch. The protocol required ECG recordings to be taken first in a sitting posture, followed by a... (More)
BACKGROUND: Long COVID and cardiovascular autonomic dysfunction, including postural orthostatic tachycardia syndrome (POTS), present significant healthcare challenges. Long-term monitoring is challenging due to the evolving nature of symptoms and the limited availability of objective diagnostic tools. With over 200 million electrocardiogram (ECG)-enabled smartwatches sold worldwide, these devices offer a promising solution for at-home diagnostics and disease tracking.
METHODS AND RESULTS: This study examines a 35-year-old male with long COVID, POTS, and chronic fatigue syndrome (CFS), who recorded 328 ECGs over using a Samsung smartwatch. The protocol required ECG recordings to be taken first in a sitting posture, followed by a standing position, with slow, controlled breathing. For testing, the patient used a Samsung smartwatch to perform a 30-s hand-to-hand single-lead ECG while engaging in 0.1 Hz diaphragmatic controlled breathing, consisting of 5 s of inhalation followed by 5 s of exhalation ( Appendix 1). S-/R-peak amplitude ratios, heart rhythm changes, and other biomarkers were analysed to assess autonomic function. Fatigue levels were self-reported via the BREATHE FLOW app using a three-grade scale, and health status was tracked monthly with the EQ-5D-5L model. Initially, the patient experienced severe fatigue and heart rhythm changes consistent with POTS. Electrocardiogram analysis revealed an increased S-wave amplitude and higher S/R ratio in standing posture, along with worsening respiratory sinus arrhythmia (RSA), indicating cardiorespiratory desynchrony. Over time, as symptoms improved, heart rate responses between sitting and standing normalized, and S/R ratio and RSA index followed self-reported fatigue levels, including fluctuations due to post-exercise fatigue.
CONCLUSION: Smartwatch-derived S-/R-wave amplitude ratio may serve as an accessible biomarker for tracking disease progression in long COVID. Given the widespread availability of smartwatches, standardized at-home protocols could improve diagnostics and monitoring for autonomic dysfunction.
(Less)
- author
- Kranck, Gustaf
; Ståhlberg, Marcus
; Andersson, Ulf
; Lundin, Johan
and Fedorowski, Artur
LU
- publishing date
- 2025-10
- type
- Contribution to journal
- publication status
- published
- subject
- in
- European Heart Journal - Case Reports
- volume
- 9
- issue
- 10
- article number
- ytaf425
- publisher
- Oxford University Press
- external identifiers
-
- pmid:41050528
- scopus:105017658479
- ISSN
- 2514-2119
- DOI
- 10.1093/ehjcr/ytaf425
- language
- English
- LU publication?
- no
- additional info
- © The Author(s) 2025. Published by Oxford University Press on behalf of the European Society of Cardiology.
- id
- b074aea3-ea49-4240-ae25-5637a3085ee1
- date added to LUP
- 2025-10-13 16:16:54
- date last changed
- 2025-11-25 07:57:57
@article{b074aea3-ea49-4240-ae25-5637a3085ee1,
abstract = {{<p>BACKGROUND: Long COVID and cardiovascular autonomic dysfunction, including postural orthostatic tachycardia syndrome (POTS), present significant healthcare challenges. Long-term monitoring is challenging due to the evolving nature of symptoms and the limited availability of objective diagnostic tools. With over 200 million electrocardiogram (ECG)-enabled smartwatches sold worldwide, these devices offer a promising solution for at-home diagnostics and disease tracking.</p><p>METHODS AND RESULTS: This study examines a 35-year-old male with long COVID, POTS, and chronic fatigue syndrome (CFS), who recorded 328 ECGs over using a Samsung smartwatch. The protocol required ECG recordings to be taken first in a sitting posture, followed by a standing position, with slow, controlled breathing. For testing, the patient used a Samsung smartwatch to perform a 30-s hand-to-hand single-lead ECG while engaging in 0.1 Hz diaphragmatic controlled breathing, consisting of 5 s of inhalation followed by 5 s of exhalation ( Appendix 1). S-/R-peak amplitude ratios, heart rhythm changes, and other biomarkers were analysed to assess autonomic function. Fatigue levels were self-reported via the BREATHE FLOW app using a three-grade scale, and health status was tracked monthly with the EQ-5D-5L model. Initially, the patient experienced severe fatigue and heart rhythm changes consistent with POTS. Electrocardiogram analysis revealed an increased S-wave amplitude and higher S/R ratio in standing posture, along with worsening respiratory sinus arrhythmia (RSA), indicating cardiorespiratory desynchrony. Over time, as symptoms improved, heart rate responses between sitting and standing normalized, and S/R ratio and RSA index followed self-reported fatigue levels, including fluctuations due to post-exercise fatigue. </p><p>CONCLUSION: Smartwatch-derived S-/R-wave amplitude ratio may serve as an accessible biomarker for tracking disease progression in long COVID. Given the widespread availability of smartwatches, standardized at-home protocols could improve diagnostics and monitoring for autonomic dysfunction.</p>}},
author = {{Kranck, Gustaf and Ståhlberg, Marcus and Andersson, Ulf and Lundin, Johan and Fedorowski, Artur}},
issn = {{2514-2119}},
language = {{eng}},
number = {{10}},
publisher = {{Oxford University Press}},
series = {{European Heart Journal - Case Reports}},
title = {{Monitoring of cardiorespiratory vagal desynchrony using novel biomarkers derived from smartwatch electrocardiograms in a patient recovering from long COVID : case report}},
url = {{http://dx.doi.org/10.1093/ehjcr/ytaf425}},
doi = {{10.1093/ehjcr/ytaf425}},
volume = {{9}},
year = {{2025}},
}