@article{BuchhornBaumannWillaschek2021, author = {Buchhorn, Reiner and Baumann, Christoph and Willaschek, Christian}, title = {Pathophysiological mechanisms of bradycardia in patients with anorexia nervosa}, series = {Health Science Reports}, volume = {4}, journal = {Health Science Reports}, number = {3}, doi = {10.1002/hsr2.331}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-244724}, year = {2021}, abstract = {Background The purpose of this investigation was to examine heart rate variability (HRV), interbeat interval (IBI), and their interrelationship in healthy controls, bradycardic hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) mutation carriers, and patients with anorexia nervosa (AN). We tested the hypothesis that neural mechanisms cause bradycardia in patients with AN. Therefore, we assumed that saturation of the HRV/IBI relationship as a consequence of sustained parasympathetic control of the sinus node is exclusively detectable in patients with AN. Methods Patients with AN between the ages of 12 and 16 years admitted to our hospital due to malnutrition were grouped and included in the present investigation (N = 20). A matched-pair group with healthy children and adolescents was created. Groups were matched for age and sex. A 24-hour Holter electrocardiography (ECG) was performed in controls and patients. More specifically, all patients underwent two 24-hour Holter ECG examinations (admission; refeeding treatment). Additionally, the IBI was recorded during the night in HCN4 mutation carriers (N = 4). HRV parameters were analyzed in 5-minute sequences during the night and plotted against mean corresponding IBI length. HRV, IBI, and their interrelationship were examined using Spearman's rank correlation analyses, Mann-Whitney U tests, and Wilcoxon signed-rank tests. Results The relationship between IBI and HRV showed signs of saturation in patients with AN. Furthermore, signs of HRV saturation were present in two HCN4 mutation carriers. In contrast, signs of HRV saturation were not present in controls. Conclusions The existence of HRV saturation does not support the existence of parasympathetically mediated bradycardia. Nonneural mechanisms, such as HCN4 downregulation, may be responsible for bradycardia and HRV saturation in patients with AN.}, language = {en} } @article{GronwaldHoos2020, author = {Gronwald, Thomas and Hoos, Olaf}, title = {Correlation properties of heart rate variability during endurance exercise: A systematic review}, series = {Annals of Noninvasive Electrocardiology}, volume = {25}, journal = {Annals of Noninvasive Electrocardiology}, number = {1}, doi = {10.1111/anec.12697}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-213548}, year = {2020}, abstract = {Background Non-linear measures of heart rate variability (HRV) may provide new opportunities to monitor cardiac autonomic regulation during exercise. In healthy individuals, the HRV signal is mainly composed of quasi-periodic oscillations, but it also possesses random fluctuations and so-called fractal structures. One widely applied approach to investigate fractal correlation properties of heart rate (HR) time series is the detrended fluctuation analysis (DFA). DFA is a non-linear method to quantify the fractal scale and the degree of correlation of a time series. Regarding the HRV analysis, it should be noted that the short-term scaling exponent alpha1 of DFA has been used not only to assess cardiovascular risk but also to assess prognosis and predict mortality in clinical settings. It has also been proven to be useful for application in exercise settings including higher exercise intensities, non-stationary data segments, and relatively short recording times. Method Therefore, the purpose of this systematic review was to analyze studies that investigated the effects of acute dynamic endurance exercise on DFA-alpha1 as a proxy of correlation properties in the HR time series. Results The initial search identified 442 articles (351 in PubMed, 91 in Scopus), of which 11 met all inclusion criteria. Conclusions The included studies show that DFA-alpha1 of HRV is suitable for distinguishing between different organismic demands during endurance exercise and may prove helpful to monitor responses to different exercise intensities, movement frequencies, and exercise durations. Additionally, non-linear DFA of HRV is a suitable analytical approach, providing a differentiated and qualitative view of exercise physiology.}, language = {en} } @article{GronwaldRogersHoos2020, author = {Gronwald, Thomas and Rogers, Bruce and Hoos, Olaf}, title = {Fractal Correlation Properties of Heart Rate Variability: A New Biomarker for Intensity Distribution in Endurance Exercise and Training Prescription?}, series = {Frontiers in Physiology}, volume = {11}, journal = {Frontiers in Physiology}, issn = {1664-042X}, doi = {10.3389/fphys.2020.550572}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212429}, year = {2020}, abstract = {Exercise and training prescription in endurance-type sports has a strong theoretical background with various practical applications based on threshold concepts. Given the challenges and pitfalls of determining individual training zones on the basis of subsystem indicators (e.g., blood lactate concentration, respiratory parameters), the question arises whether there are alternatives for intensity distribution demarcation. Considering that training in a low intensity zone substantially contributes to the performance outcome of endurance athletes and exceeding intensity targets based on a misleading aerobic threshold can lead to negative performance and recovery effects, it would be desirable to find a parameter that could be derived via non-invasive, low cost and commonly available wearable devices. In this regard, analytics conducted from non-linear dynamics of heart rate variability (HRV) have been adapted to gain further insights into the complex cardiovascular regulation during endurance-type exercise. Considering the reciprocal antagonistic behavior and the interaction of the sympathetic and parasympathetic branch of the autonomic nervous system from low to high exercise intensities, it may be promising to use an approach that utilizes information about the regulation quality of the organismic system to determine training-intensity distribution. Detrended fluctuation analysis of HRV and its short-term scaling exponent alpha1 (DFA-alpha1) seems suitable for applied sport-specific settings including exercise from low to high intensities. DFA-alpha1 may be taken as an indicator for exercise prescription and intensity distribution monitoring in endurance-type sports. The present perspective illustrates the potential of DFA-alpha1 for diagnostic and monitoring purposes as a "global" system parameter and proxy for organismic demands.}, language = {en} } @article{NagaiFoersterDote2022, author = {Nagai, Michiaki and F{\"o}rster, Carola Yvette and Dote, Keigo}, title = {Sex hormone-specific neuroanatomy of Takotsubo syndrome: is the insular cortex a moderator?}, series = {Biomolecules}, volume = {12}, journal = {Biomolecules}, number = {1}, issn = {2218-273X}, doi = {10.3390/biom12010110}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254776}, year = {2022}, abstract = {Takotsubo syndrome (TTS), a transient form of dysfunction in the heart's left ventricle, occurs predominantly in postmenopausal women who have emotional stress. Earlier studies support the concept that the human circulatory system is modulated by a cortical network (consisting of the anterior cingulate gyrus, amygdala, and insular cortex (Ic)) that plays a pivotal role in the central autonomic nervous system in relation to emotional stressors. The Ic plays a crucial role in the sympathovagal balance, and decreased levels of female sex hormones have been speculated to change functional cerebral asymmetry, with a possible link to autonomic instability. In this review, we focus on the Ic as an important moderator of the human brain-heart axis in association with sex hormones. We also summarize the current knowledge regarding the sex-specific neuroanatomy in TTS.}, language = {en} }