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Letter to the Editor: Anchoring composite electrocardiography–heart rate variability indices to a reference standard - the authors’ reply
Illya A Chaikovsky, Department of Contactless Control Systems, V.M. Glushkov Institute of Cybernetics of the National Academy of Sciences, Kyiv 03187, Ukraine
Illya A Chaikovsky, Dmytro O Dziuba, Оleg A Loskutov, Department of Anaesthesiology and Intensive Care, Shupyk National Healthcare University, Kyiv 04112, Ukraine
Olga A Kryvova, Department of Medical Information Technologies, International Research and Training Center of the National Academy of Sciences, Kyiv 03187, Ukraine
Kyrylo S Malakhov, Microprocessor Technology Lab, V.M. Glushkov Institute of Cybernetics of the National Academy of Sciences, Kyiv 03187, Ukraine
Oleksandr P Romanchuk, Department of Internal and Family Medicine, Lesya Ukrainka Volyn National University, Lutsk 43025, Ukraine
Oleksandr P Romanchuk, Department of Therapy and Rehabilitation, Ivan Boberskyi Lviv State University of Physical Culture, Lviv 79007, Ukraine
Borys M Todurov, Department of Cardiosurgery, X-ray and Extracorporeal Technologies, Shupyk National Healthcare University, Kyiv 04112, Ukraine
Borys M Todurov, Department of Extracorporeal Methods of Treatment, Heart Institute Ministry of Health of Ukraine, Kyiv 02166, Ukraine
Оleg A Loskutov, Department of Anaesthesiology and Intensive Care for Infectious Diseases, Clinical Hospital No. 4, Kyiv 02000, Ukraine
Author contributions: Chaikovsky IA, Romanchuk OP, Loskutov OA and Malakhov KS drafted the reply and revised it critically for important intellectual content; Dziuba DO, Kryvova OA, Malakhov KS and Todurov BM contributed to the conception, interpretation and critical revision of the manuscript; and all authors have read and approved the final version of the manuscript.
AI contribution statement: During the preparation of this work, the authors used ChatGPT (OpenAI) to generate an initial draft of this reply. After using this tool, the authors critically reviewed, fact-checked, and substantially revised all content and take full responsibility for the content of the publication. The tool is not listed as an author and was not used to generate or analyse study data or to create figures.
Conflict-of-interest statement: All authors declare that they have no conflicts of interest related to this work.
Corresponding author: Oleksandr P Romanchuk, MD, PhD, DM, Full Professor, Professor, Department of Internal and Family Medicine, Lesya Ukrainka Volyn National University, Bankova Street, 9, Lutsk 43025, Ukraine. romanchuk.oleksandr@vnu.edu.ua
Received: June 23, 2026
Revised: August 14, 2026
Accepted: September 8, 2026
Published online: September 26, 2026
Processing time: 89 Days and 6.3 Hours
Revised: August 14, 2026
Accepted: September 8, 2026
Published online: September 26, 2026
Processing time: 89 Days and 6.3 Hours
Core Tip
Core Tip: Composite electrocardiography and heart rate variability indices can flag small post-procedural changes that the routine 12-lead electrocardiogram misses, but they cannot separate injury from recovery unless anchored to an accepted reference standard. In this reply we set out how that anchor — paired high-sensitivity troponin and late gadolinium enhancement on cardiac magnetic resonance, with injury pre-specified by the Fourth Universal Definition of Myocardial Infarction — will be built into a larger, prospective, presentation-stratified study. We distinguish the validated construction of the composite indices from the exploratory within-cohort clustering, which still requires independent validation before any clinical use.