PSI - Issue 40

Vasily V. Gagiev et al. / Procedia Structural Integrity 40 (2022) 162–165

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Vasily V. Gagiev at al./ Structural Integrity Procedia 00 (2022) 000 – 000

to 0.04 Hz, low-frequency power from 0.04 to 0.15 Hz, and high-frequency power from 0.01 to 0.4 Hz) is known. In stepwise regression analysis with inclusion of other risk factors, the low-frequency power of heart rate (P<0.0001) at reduction by 1 SD was related to increasing mortality from all causes by a factor of 1.7 (95% confidence interval 1.37 – 2.09). It was concluded that HRV offers independent predictive information apart from that given by the evaluation of conventional risk factors Tsuji at al. (1994). The investigation of HRV for estimating the intraoperative condition of the recurrent nerve subjected to the risk of complications was reported in a complex of conventional studies Saugel at al. (2018), Singh at al. (2020), Durante at al. (2018), Ulmer at al. (2011), Bellevicine at al. (2020), Schneider at al. (2016); however, no conclusion about the usefulness of the technique of estimating the state of autonomic regulation was made. In a Brazilian intercenter study negative results of applying the technique in patients with hypo- and hyperthyroidism were obtained Peixoto de Miranda at al. (2017). This study is aimed at estimating the state of autonomic regulation in thyroid cancer patients.

Nomenclature HRV heart rate variability RCG

high-resolution rhythmocardiography

VLF

very low frequency

2. Illustrations The selected group included 20 patients with thyroid nodules, with established indications for surgery Beltsevich at al. (2017). The results of the study of 47 industrial workers without evident pathology of internals, with high load tolerance according to exercise ECG testing, were taken as control. All the patients underwent rhythmocardiography (RCG) at admission to hospital, during and after surgery. High-resolution RCG is intended for precise analysis of HRV. The method is physiologically based on the evaluation of three heart rate regulation factors, namely sympathetic, parasympathetic (fast regulation), and humoral metabolic. The HRV indicators are as follows: the average value of systolic time intervals RR, the standard deviation of all intervals SDNN, the rms deviation of humoral metabolic waves ( ϭ l ), sympathetic waves ( ϭ m ), and parasympathetic waves ( ϭ s ). Spectral analysis was used to reveal the degree of the manifestation of each regulation type affecting the heart rhythm. Fast Fourier transformation was applied. After the expansion of the HRV structure into particular harmonics, the Hamming and Parzen spectral windows were used. The following indicators were selected in the spectral analysis: very low frequency (VLF%) – the spectral share of the humoral metabolic effect on the heart rhythm in the very low frequency range of spectral power; low frequency (LF%) – the sympathetic regulation of the heart rhythm; high frequency (HF%) – the parasympathetic regulation of the heart rhythm in percentage of the total spectrum taken to be 100%. The recording was made with the use of stimulating tests with respect to RCG at rest (Ph), namely the Valsalva – Bürger parasympathetic maneuver (Vm), the Aschner humoral test (рА), predominantly sympathetic active orthostatic test (Аор), and exercise tolerance test graduated in terms of HR120 (PWC120). The result is presented as a rhythm cardiogram, whose elements are systolic time intervals accurate to 1000±3 Hz. The Z criterion, analogous to the Т criterio n for non-parametric sampling was used to prove the reliability. The values of Z ranging from 1.96 to 2.3 testify to the significance of the differences in the analyzed sets of variate values with an error of 5% and 1%, respectively. 3. Results and discussion After surgery and histology, the patients were divided into two subgroups according to the final results: 8 patients with oncologic pathology (TC) and 14 patients with thyroid follicular adenoma (TFA). The results of the HRV study for the TC patients are shown in Table 1.