Mackay, Zoë, Shah, Samit, Villalobos, Jose Gomez et al. · American journal of physiology. Heart and circulatory physiology · 2026 · DOI
This observational study reports that among 261 patients diagnosed with a heart condition called ANOCA (angina with non-obstructive coronary arteries), approximately 18% also had ME/CFS. In a separate group of 27 ME/CFS patients, 24 (89%) were found to have ANOCA when tested. The study used two diagnostic approaches—coronary function testing and exercise testing—to characterize heart and muscle responses during exertion, observing that ME/CFS patients showed a pattern of reduced muscle oxygen uptake despite normal oxygen delivery. These are early findings from a single centre and require confirmation through larger, prospective studies.
This study documents an observed association between ME/CFS and ANOCA that may have clinical implications for patients experiencing exertional chest pain, as diagnosis of ANOCA prompted management changes in the majority of cases. The haemodynamic phenotyping using iCPET provides preliminary evidence of a physiological pattern (impaired oxygen extraction at the muscle level) in ME/CFS, which could inform future mechanistic research and patient stratification strategies.
This observational study does not establish that ANOCA causes ME/CFS or vice versa, only that the two conditions are observed together at higher-than-expected frequency. The findings do not generalise beyond this single centre's patient population and cannot be assumed to represent the broader ME/CFS or ANOCA populations. The study does not confirm a mechanism for exertional limitation and does not provide a treatment recommendation; prospective validation with larger sample sizes and healthy controls is needed before clinical application.
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
Mackay, Zoë, Shah, Samit, Villalobos, Jose Gomez, Latif, Nida, Arun, Adith, Joseph, Phillip, et al. (2026). Hemodynamic Phenotyping in ME/CFS and ANOCA: Complementary Insights from Coronary Function Testing and Invasive Cardiopulmonary Exercise Testing.. American journal of physiology. Heart and circulatory physiology. https://doi.org/10.1152/ajpheart.90080.2026
BibTeX
@article{mecfsatlas-mackay-2026-hemodynamic-phenotyping,
author = {Mackay, Zoë and Shah, Samit and Villalobos, Jose Gomez and Latif, Nida and Arun, Adith and Joseph, Phillip and Heerdt, Paul and Singh, Inderjit},
title = {Hemodynamic Phenotyping in ME/CFS and ANOCA: Complementary Insights from Coronary Function Testing and Invasive Cardiopulmonary Exercise Testing.},
journal = {American journal of physiology. Heart and circulatory physiology},
year = {2026},
doi = {10.1152/ajpheart.90080.2026},
note = {PubMed: 42767811},
url = {https://www.mecfsatlas.com/evidence/mackay-2026-hemodynamic-phenotyping},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-09-22. https://www.mecfsatlas.com/evidence/mackay-2026-hemodynamic-phenotyping
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