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Frequency-Domain Features and Low-Frequency Synchronization of Photoplethysmographic Waveform Variability and Heart Rate Variability with Increasing Severity of Cardiovascular Diseases
Heart rate variability (HRV) and photoplethysmographic waveform variability (PPGV) are available approaches for assessing the state of cardiovascular autonomic regulation. The goal of our study was to compare the frequency-domain features and low-frequency (LF) synchro nization of the PPGV and HRV with increasing severity of cardiovascular diseases. Methods—Our study included 998 electrocardiogram (ECG) and finger photoplethysmogram (PPG) recordings from Citation: Kiselev, A.R.; Posnenkova, O.M.; Karavaev, A.S.; Shvartz, V.A.; Novikov, M.Y.; Gridnev, V.I. Frequency-Domain Features and Low-Frequency Synchronization of Photoplethysmographic Waveform Variability and Heart Rate Variability with Increasing Severity of Cardiovascular Diseases. Biomedicines 2024, 12, 2088. https://doi.org/ 10.3390/biomedicines12092088 Academic Editor: Nikolaos Kadoglou Received: 9 August 2024 Revised: 5 September 2024 Accepted: 9 September 2024 Published: 12 September 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). subjects, classified into five categories: 53 recordings from healthy subjects, aged 28.1 6.2 years, 536 recordings from patients with hypertension (HTN), 49.0 8.8 years old, 185 recordings from individuals with stable coronary artery disease (CAD) (63.9 9.3 years old), 104 recordings from patients with myocardial infarction (MI) that occurred three months prior to the recordings (PMI) (65.1 11.0 years old), and 120 recordings from study subjects with acute myocardial infarction (AMI) (64.7 11.5 years old). Spectral analyses of the HRV and PPGV were carried out, along with an assessment of the synchronization strength between LF oscillations of the HRV and of PPGV (synchronization index). Results—Changes in all frequency-domain indices and the synchronization index were observed along the following gradient: healthy subjects patients with HTN patients with CAD patients with PMI patients with AMI. Similar frequency-domain indices of the PPGVandHRVshowlittle relationship with each other. Conclusions—The frequency-domain indices of the PPGV are highly sensitive to the development of any cardiovascular disease and, therefore, are superior to the HRV indices in this regard. The S index is an independent parameter from the frequency-domain indices.