@article{WesselSchumannWesseletal.2000,
  author    = {Wessel, Niels and Schumann, Agnes and Wessel, Niels and Schumann, Agnes and Schirdewan, Alexander and Voss, Andreas and Kurths, J{\"u}rgen},
  title     = {Entropy measures in heart rate variability data},
  year      = {2000},
  language  = {en}
}
@article{WesselSchirdewan2006,
  author    = {Wessel, Niels and Schirdewan, Alexander},
  title     = {Toward a prediction of sudden death in propofol-related infusion syndrome},
  year      = {2006},
  language  = {en}
}
@article{WaltherWesselMalbergetal.2006,
  author    = {Walther, T and Wessel, Niels and Malberg, Hagen and Voss, Andreas and Stepan, H and Faber, R},
  title     = {A combined technique for predicting pre-eclampsia : concurrent measurement of uterine perfusion and analysis of heart rate and blood pressure variability},
  year      = {2006},
  abstract  = {Objective Pre-eclampsia is a serious complication of pregnancy with high morbidity and mortality and an incidence of 3-5\% in all pregnancies. Early prediction is still insufficient in clinical practice. Although most pre- eclamptic patients have pathological uterine perfusion in the second trimester, perfusion disturbance has a positive predictive accuracy (PPA) only of approximately 30\%. Methods Non-invasive continuous blood pressure recordings were taken simultaneously via a finger cuff for 30 min. Time series of systolic as well as diastolic beat-to-beat pressure values were extracted to analyse heart rate and blood pressure variability and baroreflex sensitivity in 102 second- trimester pregnancies, to assess predictability for pre-eclampsia (n = 16). All women underwent Doppler investigations of the uterine arteries. Results We identified a combination of three variability and baroreflex parameters to best predict pre-eclampsia several weeks before clinical manifestation. The discriminant function of these three parameters classified patients with later pre-eclampsia with a sensitivity of 87.5\%, a specificity of 83.7\%, and a PPA of 50.0\%. Combined with Doppler investigations of uterine arteries, PPA increased to 71.4\%. Conclusions This technique of incorporating one-stop clinical assessment of uterine perfusion and variability parameters in the second trimester produces the most effective prediction of pre-eclampsia to date},
  language  = {en}
}
@article{CarvajalWesselVallverduetal.2005,
  author    = {Carvajal, R. and Wessel, Niels and Vallverdu, M. and Caminal, P. and Voss, Andreas},
  title     = {Correlation dimension analysis of heart rate variability in patients with dilated cardiomyopathy},
  issn      = {0169-2607},
  year      = {2005},
  abstract  = {A correlation dimension analysis of heart rate variability (HRV) was applied to a group of 55 patients with dilated cardiomyopathy (DCM) and 55 healthy subjects as controls. The 24-h RR time series for each subject was divided into segments of 10,000 beats to determine the correlation dimension (CD) per segment. A study of the influence of the time delay (tag) in the calculation of CD was performed. Good discrimination between both groups (p < 0.005) was obtained with tag values of 5 or greater. CD values of DCM patients (8.4 ± 1.9) were significantly lower than CD values for controls (9.5 ± 1.9). An analysis of CD values of HRV showed that for healthy people, CD night values (10.6 ± 1.8) were significant greater than CD day values (9.2 ± 1.9), revealing a circadian rhythm. In DCM patients, this circadian rhythm was lost and there were no differences between CD values in day (8.8 ± 2.4) and night (8.9 ± 2. 1). © 2005 Elsevier Ireland Ltd. All rights reserved},
  language  = {en}
}
@article{HeringerWaltherMoreiraWesseletal.2005,
  author    = {Heringer-Walther, Silvia and Moreira, M. C. V. and Wessel, Niels and Saliba, J. L. and Silvia-Barra, J. and Pena, J. L. B. and Becker, S. and Siems, W. E. and Schultheiss, H. P. and Walther, T.},
  title     = {Brain natriuretic peptide predicts survival in Chagas' disease more effectively than atrial natriuretic peptide},
  issn      = {1355-6037},
  year      = {2005},
  language  = {en}
}
@phdthesis{Wessel2005,
  author    = {Wessel, Niels},
  title     = {Data analysis and modeling of the cardiovascular system},
  address   = {Potsdam},
  pages     = {Getr. Z{\"a}hlung : graph. Darst.},
  year      = {2005},
  language  = {en}
}
@article{WesselMalbergWalther2004,
  author    = {Wessel, Niels and Malberg, Hagen and Walther, T.},
  title     = {Heart rate turbulence : higher predictive value than other risk stratifiers?},
  issn      = {0009-7322},
  year      = {2004},
  language  = {en}
}
@article{BauernschmittMalbergWesseletal.2004,
  author    = {Bauernschmitt, Robert and Malberg, Hagen and Wessel, Niels and Kopp, B. and Schirmbeck, E. U. and Lange, R.},
  title     = {Impairment of cardiovascular autonomic control in patients early after cardiac surgery},
  issn      = {1010-7940},
  year      = {2004},
  abstract  = {Objective: Impairment of the baroreceptor reflex activity reflects an alteration of the autonomous regulation of the cardiovascular system and has proven to predict fatal outcome in patients after acute myocardial infarction. The following study was performed to analyse the baroreceptor sensitivity, heart rate variability and blood pressure variability in patients early after coronary surgery. Methods: Twenty-five male patients undergoing coronary artery bypass were examined in a prospective study; normal values were obtained from healthy volunteers. Arterial pressure signals were recorded from a radial artery catheter for 30 min preoperatively and in short intervals after surgery. Mechanical manipulations and pharmacological interventions were avoided during the sampling periods. Baroreflex function was calculated according to the dual sequence method, heart rate variability and blood pressure variability were calculated including nonlinear methods. Results: Initial values of the patients did not differ from healthy volunteers. The strength of baroreflex sensitivity (increase in blood pressure causing a synchronous decrease of heart rate) is low 2 It postoperatively. The number of delayed tachycardic changes of heart rate, which are caused by sympathetic activation, is only moderately reduced as compared to values obtained from healthy volunteers. Heart rate variability is widely unchanged as compared to preoperative values; blood pressure variability showed an increase of low-frequency components, again indicating sympathetic predominance. Nonlinear analyses revealed reduced system complexity at the beginning of the postoperative course. Conclusion: Obviously, there is a vagal suppression 20 h after surgery, while the sympathetic tonus works in a normal range. This unbalanced interaction of the autonomous systems is similar to findings in patients after myocardial infarction. The predictive value of these markers has to be elucidated in further clinical studies. (C) 2003 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{BaumertBaierHaueisenetal.2004,
  author    = {Baumert, M. and Baier, V. and Haueisen, J. and Wessel, Niels and Meyerfeldt, Udo and Schirdewan, Alexander and Voss, Andreas},
  title     = {Forecasting of life threatening arrhythmias using the compression entropy of heart rate},
  issn      = {0026-1270},
  year      = {2004},
  abstract  = {Objectives. Ventricular tachycardia (VT) provoking sudden cardiac death (SCD) are a major cause of mortality in the developed countries. The most efficient therapy for SCID prevention are implantable cardioverter defibrillators (ICD). In this study heart rate variability (HRV) measures were analyzed for short-term forecasting of VT in order to improve VT sensing and to enable a patient warning of forthcoming shocks. Methods. The lost 1000 normal beat-to-beat intervals before 50 VT episodes stored by the ICD were analyzed and compared to individually acquire control time series (CON). HRV analysis was performed with standard parameters of time and frequency domain as suggested by the HRV Task Force and furthermore with a newly developed and optimized nonlinear parameter that assesses the compression entropy of heart rate (H-c). Results. Except of meanNN (p = 0.02) we found no significant differences in standard HRV parameters. In contrast, H, revealed highly significant (p = 0.007) alterations in VT compared with CON suggesting a decreased complexity before the onset of VT. Conclusion: Compression entropy might be a suitable parameter for short-term forecasting of life-threatening tachycardia in ICD},
  language  = {en}
}
@article{FaberBaumertStepanetal.2004,
  author    = {Faber, R. and Baumert, M. and Stepan, H. and Wessel, Niels and Voss, Andreas and Walther, T.},
  title     = {Baroreflex sensitivity, heart rate, and blood pressure variability in hypertensive pregnancy disorders},
  issn      = {0950-9240},
  year      = {2004},
  abstract  = {Hypertensive pregnancy disorders are a leading cause of perinatal and maternal morbidity and mortality. Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) are relevant predictors of cardiovascular risk in humans. The aim of the study was to evaluate whether HRV, BPV, and BRS differ between distinct hypertensive pregnancy disorders. Continuous heart rate and blood pressure recordings were performed in 80 healthy pregnant women as controls (CON), 19 with chronic hypertension (CH), 18 with pregnancy-induced hypertension (PIH), and 44 with pre-eclampsia (PE). The data were assessed by time and frequency domain analysis, nonlinear dynamics, and BRS. BPV is markedly altered in all three groups with hypertensive disorders compared to healthy pregnancies, whereby changes were most pronounced in PE patients. Interestingly, this increase in PE patients did not lead to elevated spontaneous baroreflex events, while BPV changes in both the other hypertensive groups were paralleled by alterations in baroreflex parameters. The HRV is unaltered in CH and PE but significantly impaired in PIH. We conclude that parameters of the HRV, BPV, and BRS differ between various hypertensive pregnancy disorders. Thus, distinct clinical manifestations of hypertension in pregnancy have different pathophysiological, regulatory, and compensatory mechanisms},
  language  = {en}
}