Browsing by Author "Kazdagli H."

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    A simple approach to determine loss of physiological complexity in heart rate series
    (Institute of Physics, 2023) Ozel H.F.; Kazdagli H.
    There are several ways to assess complexity, but no method has yet been developed for quantitatively calculating the ‘loss of fractal complexity’ under pathological or physiological states. In this paper, we aimed to quantitatively evaluate fractal complexity loss using a novel approach and new variables developed from Detrended Fluctuation Analysis (DFA) log-log graphics. Three study groups were established to evaluate the new approach: one for normal sinus rhythm (NSR), one for congestive heart failure (CHF), and white noise signal (WNS). ECG recordings of the NSR and CHF groups were obtained from PhysioNET Database and were used for analysis. For all groups Detrended Fluctuation Analysis scaling exponents (DFAα 1, DFAα 2) were determined. Scaling exponents were used to recreate the DFA log-log graph and lines. Then, the relative total logarithmic fluctuations for each sample were identified and new parameters were computed. To do this, we used a standard log-log plane to standardize the DFA log-log curves and calculated the differences between the standardized and expected areas. We quantified the total difference in standardized areas using parameters called dS1, dS2, and TdS. Our results showed that; compared to the NSR group, DFAα 1 was lower in both CHF and WNS groups. However, DFAα 2 was only reduced in the WNSgroup and not in the CHFgroup. Newly derived parameters: dS1, dS2, and TdS were significantly lowerin the NSR group compared to the CHF and WNS groups. The new parameters derived from the DFA log-log graphs are highly distinguishing for congestive heart failure and white noise signal. In addition, it may be concluded that a potential feature of our approach can be beneficial in classifying the severity of cardiac abnormalities. © 2023 IOP Publishing Ltd.
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    Electrophysiological detection of exam stress in health schools' students
    (Akademiai Kiado ZRt., 2024) Kazdagli H.; Ozel H.F.; Ozturk S.; Ceylan D.; Erdeniz B.; Ozbek M.; Semin M.I.
    Anxiety is a common issue among university students, many of them experience anxiety, depression, and stress during their school life. This study aimed to compare the acute physiological stress responses of students divided into two groups according to their perceived anxiety levels (positive test anxiety, PTA+, and negative test anxiety, PTA-). Heart rate variability (HRV) and electrodermal activity (EDA) were used to assess stress. Thirty-one healthy volunteers participated in the study. Participants completed anxiety assessments, including the Westside Test Anxiety Scale (WTAS), the State-Trait Anxiety Inventory (STAI), and the Test State Anxiety Inventory (TSAI). Based on their scores, participants were categorized into PTA+ and PTA-groups. All participants underwent 24-h continuous recordings of pulse and electrodermal activity (EDA) on two separate occasions: one day prior to a written exam and during a designated exam-free day serving as a baseline control. We compared the HRV and EDA data obtained on a regular day and on an exam day between the two groups. Results showed that the PTA+ group had significantly higher heart rate, stress index, low frequency, and short-Term detrended fluctuation analysis (DFAα1) on the exam day. The tonic EDA component was also higher in the PTA+ group. Stress-related HRV and EDA parameters were negatively correlated with exam scores. In conclusion, the study found that physiological stress indicators obtained from HRV and EDA are associated with perceived exam anxiety in students. © 2024 Akadémiai Kiadó, Budapest.
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    Evaluation of differential effects of CDP-choline and choline on parasympathetic activity and changes in choline levels with heart rate variability
    (Marmara University, 2024) Kazdagli H.; Alpay S.; Ozel H.F.; Baris E.
    Objective: Heart rate variability (HRV) is used to evaluate the autonomic activity of heartbeat. This study aimed to investigate the effects of cholinomimetic drugs cytidine diphosphate-choline (CDP-choline) and choline, on short-term HRV parameters. Materials and Methods: Animals were randomized into three groups; control (0.9% NaCl), choline (100 mg/kg), CDP-choline (400 mg/kg). Electrocardiography recordings were obtained for 45-minutes after treatments with 15-minutes intervals. HRV analyses and total choline level measurements in serum and heart tissues were performed. Results: High frequency power and total power increased in treatment groups, while heart rates were decreased. Low frequency was decreased with choline while very low frequency power decreased with CDP-choline. Choline affected most of the HRV parameters in the first 15 minutes, while the effect of CDP-choline started within 30 minutes. Total choline levels were higher in both treatment groups than in the control while the levels were also higher in the choline group compared to CDP-choline group. Conclusion: This study showed that CDP-choline and choline treatments produced a rapid response to short-term HRV parameters, while increasing tissue choline levels. Moreover, the differences in effects and onset time between the drugs on HRV might be related to tissue choline concentration. © 2024 Marmara University Press, All Rights Reserved.
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    Right vagotomy alters heart rate variability temporarily and increases total choline levels in rats
    (Walter de Gruyter GmbH, 2024) Kazdagli H.; Baris E.; Ozel H.F.; Ozbek M.
    Objectives: The variability in the time intervals between heartbeats, known as heart rate variability (HRV), serves as a reflection of the intricate interplay between the sympathetic and parasympathetic neural systems. While the potential asymmetric effects of the left and right branches of the vagus nerve remain uncertain, this study aims to investigate the impact of unilateral, bilateral, and atropine interventions on HRV parameters and choline levels within cardiac tissue. Methods: 40 male adult Wistar albino rats were randomly assigned to the five groups (each n=8): sham-operated, atropine, right vagotomy, left vagotomy, and bilateral vagotomy. Heart rate variability (HRV) analyses were conducted, and the levels of total choline/acetylcholine in heart tissues were quantified. Statistical analyses were performed to assess the results. Results: The bilateral vagotomy and atropine groups exhibited higher heart rates and high frequency power (HF), along with reduced low frequency power (LF). Total power (TP) remained relatively unchanged. In the bilateral vagotomy group, DFAα1 was significantly elevated while DFAα2 was reduced significantly. SD1 and SampEn were significantly lower in both the bilateral vagotomy and atropine groups. Notably, the right vagotomy group displayed significant changes primarily in the 15th minute, particularly in time-domain parameters, HF, TP, and SD1, with a significant increase observed in total choline levels. Conclusions: Our results revealed that asymmetrical vagal innervation induces distinct effects on heart rate variability parameters and total choline/acetylcholine levels in heart tissues. Our findings suggest that compensatory hemodynamic recovery, possibly driven by contralateral vagal overactivity, may contribute to these observed results. © 2024 the author(s), published by De Gruyter.