Kranck, Gustaf, Ståhlberg, Marcus, Andersson, Ulf et al. · European heart journal. Case reports · 2025 · DOI
Researchers tracked one long COVID patient over time using a smartwatch to record heart activity while he was sitting and standing. They noticed that when his fatigue improved, his heart's electrical patterns also normalized, suggesting smartwatch recordings could help monitor autonomic dysfunction (when the nervous system struggles to control heart rate and blood pressure). This simple at-home method may offer a practical way for patients to track their own recovery.
ME/CFS and long COVID patients often lack objective tools to track their fluctuating autonomic symptoms at home. This study demonstrates that widely available smartwatches may provide accessible, real-time biomarkers of heart-breath synchrony that correlate with fatigue and recovery, potentially enabling better self-monitoring and earlier detection of autonomic deterioration without requiring clinic visits.
This case report does not prove that S/R ratios cause fatigue or that smartwatch biomarkers are diagnostic for ME/CFS; it only shows correlation in one patient. The study cannot establish whether these metrics are specific to autonomic dysfunction in ME/CFS versus other conditions, and lacks controls to validate the biomarkers against gold-standard autonomic testing. Generalizability to other patients remains entirely unknown.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Kranck, Gustaf, Ståhlberg, Marcus, Andersson, Ulf, Lundin, Johan, & Fedorowski, Artur (2025). Monitoring of cardiorespiratory vagal desynchrony using novel biomarkers derived from smartwatch electrocardiograms in a patient recovering from long COVID: case report.. European heart journal. Case reports. https://doi.org/10.1093/ehjcr/ytaf425
BibTeX
@article{mecfsatlas-kranck-2025-monitoring-cardiorespiratory,
author = {Kranck, Gustaf and Ståhlberg, Marcus and Andersson, Ulf and Lundin, Johan and Fedorowski, Artur},
title = {Monitoring of cardiorespiratory vagal desynchrony using novel biomarkers derived from smartwatch electrocardiograms in a patient recovering from long COVID: case report.},
journal = {European heart journal. Case reports},
year = {2025},
doi = {10.1093/ehjcr/ytaf425},
note = {PubMed: 41050528},
url = {https://www.mecfsatlas.com/evidence/kranck-2025-monitoring-cardiorespiratory},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/kranck-2025-monitoring-cardiorespiratory
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