TY - JOUR A1 - Heringer-Walther, Silvia A1 - Moreira, Maria da Consolacao V. A1 - Wessel, Niels A1 - Wang, Yong A1 - Ventura, Pago Moreira A1 - Schultheiss, Heinz-Peter A1 - Walther, Thomas T1 - Does the C-type natriuretic peptide have prognostic value in Chagas disease and other dilated cardiomyopathies JF - Journal of cardiovascular pharmacology N2 - Atrial natriuretic peptides (ANP) and brain natriuretic peptides (BNP) are powerful neurohormonal indicators of left-ventricular function and prognosis in heart failure (HF). Chagas disease (CD) caused by the protozoan Trypanosoma cruzi. remains a major cause of HF in Latin America. We assessed whether the plasma concentration of the third natriuretic peptide, C-type natnuretic peptide (CNP), also has diagnostic and prognostic properties in patients with CD or other dilated cardiomyopathies (DCM). Blood samples were obtained from 66 patients with CD, 50 patients with DCM from other causes, and 30 gender- and age-matched healthy subjects. Patients were subdivided according to the New York Heart Association (NYHA) class. The CNP concentration was determined by radioimmunoassay (Immundiagnostik, Bensheim, Germany). The main duration of follow-up was 31.4 months (range 13 to 54 months), 19 patients had died and 11 patients received a heart transplant. CNP concentrations were only significantly altered in patients with DCM or CD of the NYHA classes III and IV (P < 0.05). The Pearson correlation of echocardiographic data with CNP revealed an association only with the left-ventricular end systolic volume (P = 0.03) in patients with DCM. Furthermore, CNP did not predict mortality or the necessity for heart transplant. Our data are the first to demonstrate the raised levels of the third natriuretic peptide CNP in CD and other DCM Whereas ANP and BNP have a high predictive value for mortality in both diseases, CNP is without any predictive potency. KW - cardiomyopathy KW - heart failure KW - natriuretic peptide system KW - Trypanosoma cruzi Y1 - 2006 U6 - https://doi.org/10.1097/01.fjc.0000249892.22635.46 SN - 0160-2446 VL - 48 IS - 6 SP - 293 EP - 298 PB - Lippincott Williams & Wilkins CY - Philadelphia ER - TY - JOUR A1 - Stepan, H A1 - Faber, R A1 - Wessel, Niels A1 - Wallukat, Gerd A1 - Schultheiss, H. P. A1 - Walther, T T1 - Relation between circulating angiotensin II type 1 receptor agonistic autoantibodies and soluble fms-like tyrosine kinase 1 in the pathogenesis of preeclampsia N2 - Context: Placental and circulatory soluble fms-like tyrosine kinase 1 (sFlt1) has proven to be elevated in pregnant women with preeclampsia, a disease characterized by hypertension, proteinuria, and endothelial dysfunction. Recent studies also demonstrated an autoantibody against the angiotensin II type 1 (AT1) receptor (AT1-AA) in that disease. Objective: Both factors are discussed as key players in the etiology of preeclampsia. However, it has not yet been clarified whether these two circulating factors correlate and whether synergy determines the severity of pathology. Design: AT1-AA was retrospectively determined by a bioassay and sFlt1 by an ELISA. Patients: Serum from second-trimester pregnancies with normal or abnormal uterine perfusion and in women at term with or without pregnancy pathology was analyzed. Results: Most of the preeclamptic patients were characterized by high sFlt1 levels and the presence of AT1-AA, although the agonistic effects of the antibody did not correlate with the sFlt1 concentrations (P = 0.85). Although AT1- AA was also detected in second-trimester pregnancies evidencing abnormal uterine perfusion without later pathology, sFlt1 was not significantly elevated in these pregnancies, compared with those with normal uterine perfusion. However, whereas women with abnormal perfusion and later pregnancy pathology did not differ in AT1-AA, compared with those with normal outcome, sFlt1 was significantly increased. Again, the two factors did not correlate (P = 0.15). Conclusions: We conclude that AT1-AA bioactivity and sFlt1 concentrations do not correlate, are not mutually dependent, and are thus probably involved in distinct pathogenetic mechanisms. Both factors in combination may not be causative for the early impaired trophoblast invasion and pathological uterine perfusion Y1 - 2006 UR - http://jcem.endojournals.org/content/91/6/2424.full U6 - https://doi.org/10.1210/Jc.2005-2698 ER - TY - JOUR A1 - Helland, Vanessa Carolina Figuera A1 - Gapelyuk, Andrej A1 - Suhrbier, Alexander A1 - Riedl, Maik A1 - Penzel, Thomas A1 - Kurths, Jürgen A1 - Wessel, Niels T1 - Investigation of an automatic sleep stage classification by means of multiscorer hypnogram N2 - Objectives: Scoring sleep visually based on polysomnography is an important but time-consuming element of sleep medicine. Where-as computer software assists human experts in the assignment of sleep stages to polysomnogram epochs, their performance is usually insufficient. This study evaluates the possibility to fully automatize sleep staging considering the reliability of the sleep stages available from human expert sleep scorers. Methods: We obtain features from EEG, ECG and respiratory signals of polysomnograms from ten healthy subjects. Using the sleep stages provided by three human experts, we evaluate the performance of linear discriminant analysis on the entire polysomnogram and:only on epochs where the three experts agree in their-sleep stage scoring. Results: We show that in polysomnogram intervals, to which all three scorers assign the same sleep stage, our algorithm achieves 90% accuracy. This high rate of agreement with the human experts is accomplished with only a small set of three frequency features from the EEG. We increase-the performance to 93% by including ECG and respiration features. In contrast, on intervals of ambiguous sleep stage, the sleep stage classification obtained from our algorithm, agrees with the human consensus scorer in approximately 61%. Conclusions: These findings suggest that machine classification is highly consistent with human sleep staging and that error in the algorithm's assignments is rather a problem of lack of well-defined criteria for human experts to judge certain polysomnogram epochs than an insufficiency of computational procedures Y1 - 2010 UR - http://www.schattauer.de/index.php?id=103&L=1 U6 - https://doi.org/10.3414/Me09-02-0052 SN - 0026-1270 ER - TY - JOUR A1 - Chen, Jin-Long A1 - Shiau, Yuo-Hsien A1 - Tseng, Yin-Jiun A1 - Chiu, Hung-Wen A1 - Hsiao, Tzu-Chien A1 - Wessel, Niels A1 - Kurths, Jürgen A1 - Chu, Woei-Chyn T1 - Concurrent sympathetic activation and vagal withdrawal in hyperthyroidism : evidence from detrended fluctuation analysis of heart rate variability N2 - Despite many previous Studies on the association between hyperthyroidism and the hyperadrenergic state, controversies still exist. Detrended fluctuation analysis (DFA) is a well recognized method in the nonlinear analysis of heart rate variability (HRV), and it has physiological significance related to the autonomic nervous system. In particular, an increased short-term scaling exponent alpha 1 calculated from DFA is associated with both increased sympathetic activity and decreased vagal activity. No study has investigated the DFA of HRV in hyperthyroidism. This study was designed to assess the sympathovagal balance in hyperthyroidism. We performed the DFA along with the linear analysis of HRV in 36 hyperthyroid Graves' disease patients (32 females and 4 males; age 30 +/- 1 years, means +/- SE) and 36 normal controls matched by sex, age and body mass index. Compared with the normal controls, the hyperthyroid patients revealed a significant increase (P < 0.001) in alpha 1 (hyperthyroid 1.28 +/- 0.04 versus control 0.91 +/- 0.02), long-term scaling exponent alpha 2 (1.05 +/- 0.02 versus 0.90 +/- 0.01), overall scaling exponent alpha (1.11 +/- 0.02 versus 0.89 +/- 0.01), low frequency power in normalized units (LF%) and the ratio of low frequency power to high frequency power (LF/HF); and a significant decrease (P < 0.001) in the standard deviation of the R-R intervals (SDNN) and high frequency power (HF). In conclusion, hyperthyroidism is characterized by concurrent sympathetic activation and vagal withdrawal. This sympathovagal imbalance state in hyperthyroidism helps to explain the higher prevalence of atrial fibrillation and exercise intolerance among hyperthyroid patients. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/03784371 U6 - https://doi.org/10.1016/j.physa.2009.12.062 SN - 0378-4371 ER - TY - JOUR A1 - Wessel, Niels A1 - Riedl, Maik A1 - Kurths, Jürgen T1 - Is the normal heart rate "chaotic" due to respiration? N2 - The incidence of cardiovascular diseases increases with the growth of the human population and an aging society, leading to very high expenses in the public health system. Therefore, it is challenging to develop sophisticated methods in order to improve medical diagnostics. The question whether the normal heart rate is chaotic or not is an attempt to elucidate the underlying mechanisms of cardiovascular dynamics and therefore a highly controversial topical challenge. In this contribution we demonstrate that linear and nonlinear parameters allow us to separate completely the data sets of the three groups provided for this controversial topic in nonlinear dynamics. The question whether these time series are chaotic or not cannot be answered satisfactorily without investigating the underlying mechanisms leading to them. We give an example of the dominant influence of respiration on heart beat dynamics, which shows that observed fluctuations can be mostly explained by respiratory modulations of heart rate and blood pressure (coefficient of determination: 96%). Therefore, we recommend reformulating the following initial question: "Is the normal heart rate chaotic?" We rather ask the following: " Is the normal heart rate 'chaotic' due to respiration?" Y1 - 2009 UR - http://ojps.aip.org/chaos/ U6 - https://doi.org/10.1063/1.3133128 SN - 1054-1500 ER - TY - JOUR A1 - Riedl, Maik A1 - van Leeuwen, Peter Jan A1 - Suhrbier, Alexander A1 - Malberg, Hagen A1 - Groenemeyer, Dietrich A1 - Kurths, Jürgen A1 - Wessel, Niels T1 - Testing foetal-maternal heart rate synchronization via model-based analyses N2 - The investigation of foetal reaction to internal and external conditions and stimuli is an important tool in the characterization of the developing neural integration of the foetus. An interesting example of this is the study of the interrelationship between the foetal and the maternal heart rate. Recent studies have shown a certain likelihood of occasional heart rate synchronization between mother and foetus. In the case of respiratory-induced heart rate changes, the comparison with maternal surrogates suggests that the evidence for detected synchronization is largely statistical and does not result from physiological interaction. Rather, they simply reflect a stochastic, temporary stability of two independent oscillators with time-variant frequencies. We reanalysed three datasets from that study for a more local consideration. Epochs of assumed synchronization associated with short-term regulation of the foetal heart rate were selected and compared with synchronization resulting from white noise instead of the foetal signal. Using data-driven modelling analysis, it was possible to identify the consistent influence of the heartbeat duration of maternal beats preceding the foetal beats during epochs of synchronization. These maternal beats occurred approximately one maternal respiratory cycle prior to the affected foetal beat. A similar effect could not be found in the epochs without synchronization. Simulations based on the fitted models led to a higher likelihood of synchronization in the data segments with assumed foetal-maternal interaction than in the segment without such assumed interaction. We conclude that the data-driven model-based analysis can be a useful tool for the identification of synchronization. Y1 - 2009 UR - http://rsta.royalsocietypublishing.org/ U6 - https://doi.org/10.1098/rsta.2008.0277 SN - 1364-503X ER - TY - JOUR A1 - Retzlaff, Beatrice A1 - Bauernschmitt, Robert A1 - Malberg, Hagen A1 - Brockmann, Gernot A1 - Uhl, Christian A1 - Lange, Ruediger A1 - Kurths, Jürgen A1 - Bretthauer, Georg A1 - Wessel, Niels T1 - Depression of cardiovascular autonomic function is more pronounced after mitral valve surgery : evidence for direct trauma N2 - The analysis of baroreflex sensitivity (BRS) and heart rate variability (HRV) leads to additional insights into patients' prognosis after cardiovascular events. The following study was performed to assess the differences in the post-operative recovery of autonomic regulation after mitral valve (MV) and aortic valve (AV) surgery with a heart lung machine. Among the 43 consecutive male patients enrolled in a prospective study, 26 underwent isolated AV surgery and 17 isolated MV surgery. Blood pressure as well as ECG signals were recorded the day before, 24 hours after and one week after surgery. BRS was calculated according to the dual sequence method, and HRV was calculated using standard linear as well as nonlinear parameters. There were no major differences between the two groups in the pre-operative values. At 24 hours a comparable depression of HRV and BRS in both groups was observed, while at 7 days there was partial recovery in AV patients, which was absent in MV patients: p(AV versus MV) < 0.001. While the response of the autonomic system to surgery is similar in AV and MV patients, there is obviously a decreased ability to recover in MV patients, probably attributed to traumatic lesions of the autonomic nervous system by opening the atria. Ongoing research is required for further clarification of the pathophysiology of this phenomenon and to establish strategies to restore autonomic function. Y1 - 2009 UR - http://rsta.royalsocietypublishing.org/ U6 - https://doi.org/10.1098/rsta.2008.0272 SN - 1364-503X ER - TY - JOUR A1 - Porta, Alberto A1 - Di Rienzo, Marco A1 - Wessel, Niels A1 - Kurths, Jürgen T1 - Addressing the complexity of cardiovascular regulation Y1 - 2009 UR - http://rsta.royalsocietypublishing.org/ U6 - https://doi.org/10.1098/rsta.2008.0292 SN - 1364-503X ER - TY - BOOK A1 - Malberg, Hagen A1 - Sander-Thömmes, Tilmann A1 - Wessel, Niels A1 - Wolf, Werner T1 - Biosingnalverarbeitung : Innovation bei der Erfassung und Analyse bioelektronischer und biomagnetischer Signale ; Universität Potsdam, 16.-18.07.1000 ; Tagungsband Y1 - 2008 SN - 978-3-9810021-7-1 PB - Physikalische technische Bundesanst. CY - Potsdam ER - TY - JOUR A1 - Wessel, Niels A1 - Kleiner, H. J. A1 - Voss, Andreas A1 - Kurths, Jürgen A1 - Dietz, R. T1 - Nonlinear dynamics in cardiovasscular diseases Y1 - 1997 ER -