Letter to the Editor: Anchoring composite electrocardiography–heart rate variability indices to a reference standard - the authors’ reply

doi:10.4330/wjc.124700

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World Journal of Cardiology

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1949-8462

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Baishideng Publishing Group Inc, 7041 Koll Center Parkway, Suite 160, Pleasanton, CA 94566, USA

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Copyright: ©Author(s) 2026. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial (CC BY-NC 4.0) license. No commercial re-use. See permissions. Published by Baishideng Publishing Group Inc.

World J Cardiol. Sep 26, 2026; 18(9): 124700
Published online Sep 26, 2026. doi: 10.4330/wjc.124700

Letter to the Editor: Anchoring composite electrocardiography–heart rate variability indices to a reference standard - the authors’ reply

Illya A Chaikovsky, Dmytro O Dziuba, Olga A Kryvova, Kyrylo S Malakhov, Oleksandr P Romanchuk, Borys M Todurov, Оleg A Loskutov

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 12 Hours

Abstract

We respond to the editorial of Salimi and Hematpour on our study of mild myocardial injury during percutaneous coronary intervention detected by composite electrocardiography and heart rate variability indices. We agree that these indices must be anchored to an external reference standard, and outline a prospective design using paired high-sensitivity troponin and cardiac magnetic resonance with late gadolinium enhancement, with injury pre-specified by the Fourth Universal Definition of Myocardial Infarction. We clarify that the composite indices derive from a predefined hierarchical scaling system normalized against approximately 17000 healthy individuals, whereas the within-cohort clustering is the exploratory step requiring independent validation. We acknowledge that short peri-procedural recordings are sensitive to sedation, pain and autonomic confounders, and endorse a roadmap of larger multicentre cohorts correlating the signal with biomarker kinetics, imaging and clinical outcomes.

Keywords: Percutaneous coronary intervention; Myocardial injury; Electrocardiography; Heart rate variability; Reference standard; Cardiac troponin; Cardiac magnetic resonance; Validation

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.