@phdthesis{Sevgin2023,
  author    = {Sevgin, Semanur},
  title     = {Inad{\"a}quate Sinustachykardie: Kardiovaskul{\"a}re Risikostratifizierung und Therapiekontrolle mittels Langzeit-EKG Daten von Jugendlichen},
  doi       = {10.25972/OPUS-33014},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-330148},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Inappropriate sinus tachycardia (IST) is a common disease of the autonomic nervous system in children and adults. Diagnosis and treatment of IST in adolescents is not well defined. In this retrospective study, we tested our hypothesis regarding autonomic dysfunction in childhood by analyzing 24-h heart rate variability (HRV) in 479 children, with a mean age of 13.7 ± 2.1 years, who were referred to the outpatient clinic in the Pediatrics Department within the last 15 years. Seventy-four adolescents with a mean 24-h heart rate ≥ 95 bpm (our cut-off for an IST based upon 66 healthy controls) were deemed to have IST. We found the risk of IST to be high in adolescents with attention deficit disorder (OR = 3.5,p<0.001), pre-hypertension (OR = 2.5, p = 0.043) and hypertension (OR = 2.1,p = 0.02); insignificantly enhanced in children with short stature (OR = 1.9,p = 0.19), surgically-treated congenital heart disease (OR = 1.4,p = 0.51) and obesity without hypertension (OR = 1.4;p = 0.25); and negligible in adolescents with anorexia nervosa (OR = 0.3, p = 0.26) and constitutional thinness (OR = 0.9,p = 0.89). IST was associated with a significant decrease in global HRV and elevated blood pressures, indicating an enhanced cardiovascular risk. Methylphenidate did not increase 24-h heart rates, whereas omega-3 fatty acid supplementation significantly decreased elevated heart rates and increased HRV in adolescents with IST. In this retrospective analysis, 15.4\% of adolescents suffered from IST with a 24-h heart rate ≥ 95 bpm, predominately due to attention deficit disorder and hypertension.},
  subject      = {HRV},
  language  = {de}
}
@phdthesis{Sachs2004,
  author    = {Sachs, Anke},
  title     = {Erregungsbildung und Erregungsleitung des Herzens bei HLA B27-assozierter juveniler Arthritis in Ruhe und unter k{\"o}rperlicher Belastung},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-11504},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2004},
  abstract  = {Eine Herzbeteiligung in Form von Reizleitungsst{\"o}rungen, Klappenfunktionsst{\"o}rungen und Funktionsst{\"o}rungen des Myokards bei erwachsenen Patienten mit HLA B27-positver Spondyloarthropathien ist seit langem bekannt. {\"U}berlegungen existieren, dass diese kardialen Ver{\"a}nderungen eher mit der HLA B27-Eigenschaft anstatt mit der Arthritis in Zusammenhang stehen. Der Zeitpunkt, an dem gerade die Reizbildungs- und Reizleitungsst{\"o}rungen beginnen, ist unklar. Daher verglichen wir in unserer Studie HLA B27-positive Kinder u. Jugendliche (n=22), die an einer juvenilen Form der Arthritis erkrankt waren, mit HLA B27-negativen Kindern u. Jugendlichen (n=20), die an einer Arthritis erkrankt waren, mit gesunden Kindern und Jugendlichen (n=22), deren HLA B27-Status unbekannt war. Um jegliche Ver{\"a}nderungen der Reizbildung und Reizleitung zu erkennen, analysierten wir 12-Kanal-Ruhe-EKG, EKG w{\"a}hrend maximaler k{\"o}rperlicher Anstrengung (Wingate Test) und hochaufl{\"o}sende EKG. Weder im Ruhe-EKG, noch im Verlauf der Herzfrequenz w{\"a}hrend des Wingate Testes und in der Herzfrequenzvariabilit{\"a}t, konnten wir Unterschiede zwischen den HLA B27-positiven und HLA B27-negativen Patienten aufzeigen. Bei der Analyse der Herzfrequenzvariabilit{\"a}t zeigte sich eine verringerte parasympatische Aktivit{\"a}t der an einer Arthritis-erkrankten Patienten gegen{\"u}ber den gesunden Kontrollen, die wir mit einer erh{\"o}hten sympathischen Aktivit{\"a}t bei chronisch Kranken erkl{\"a}rten. Wir halten damit St{\"o}rungen der Erregungsbildung und Erregungsleitung f{\"u}r eine Sp{\"a}tmanifestation bei Patienten mit HLA B27-assozierter Arthritis.},
  language  = {de}
}
@phdthesis{Kaufmann2013,
  author    = {Kaufmann, Tobias},
  title     = {Brain-computer interfaces based on event-related potentials: toward fast, reliable and easy-to-use communication systems for people with neurodegenerative disease},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-83441},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {Objective: Brain Computer Interfaces (BCI) provide a muscle independent interaction channel making them particularly valuable for individuals with severe motor impairment. Thus, different BCI systems and applications have been proposed as assistive technology (AT) solutions for such patients. The most prominent system for communication utilizes event-related potentials (ERP) obtained from the electroencephalogram (EEG) to allow for communication on a character-by-character basis. Yet in their current state of technology, daily life use cases of such systems are rare. In addition to the high EEG preparation effort, one of the main reasons is the low information throughput compared to other existing AT solutions. Furthermore, when testing BCI systems in patients, a performance drop is usually observed compared to healthy users. Patients often display a low signal-to-noise ratio of the recorded EEG and detection of brain responses may be aggravated due to internally (e.g. spasm) or externally induced artifacts (e.g. from ventilation devices). Consequently, practical BCI systems need to cope with mani-fold inter-individual differences. Whilst these high demands lead to increasing complexity of the technology, daily life use of BCI systems requires straightforward setup including an easy-to-use graphical user interface that nonprofessionals can handle without expert support. Research questions of this thesis: This dissertation project aimed at bringing forward BCI technology toward a possible integration into end-users' daily life. Four basic research questions were addressed: (1) Can we identify performance predictors so that we can provide users with individual BCI solutions without the need of multiple, demanding testing sessions? (2) Can we provide complex BCI technology in an automated, user-friendly and easy-to-use manner, so that BCIs can be used without expert support at end-users' homes? (3) How can we account for and improve the low information transfer rates as compared to other existing assistive technology solutions? (4) How can we prevent the performance drop often seen when bringing BCI technology that was tested in healthy users to those with severe motor impairment? Results and discussion: (1) Heart rate variability (HRV) as an index of inhibitory control (i.e. the ability to allocate attention resources and inhibit distracting stimuli) was significantly related to ERP-BCI performance and accounted for almost 26\% of variance. HRV is easy to assess from short heartbeat recordings and may thus serve as a performance predictor for ERP-BCIs. Due to missing software solutions for appropriate processing of artifacts in heartbeat data (electrocardiogram and inter-beat interval data), our own tool was developed that is available free of charge. To date, more than 100 researchers worldwide have requested the tool. Recently, a new version was developed and released together with a website (www.artiifact.de). (2) Furthermore, a study of this thesis demonstrated that BCI technology can be incorporated into easy-to-use software, including auto-calibration and predictive text entry. Na{\"i}ve, healthy nonprofessionals were able to control the software without expert support and successfully spelled words using the auto-calibrated BCI. They reported that software handling was straightforward and that they would be able to explain the system to others. However, future research is required to study transfer of the results to patient samples. (3) The commonly used ERP-BCI paradigm was significantly improved. Instead of simply highlighting visually displayed characters as is usually done, pictures of famous faces were used as stimulus material. As a result, specific brain potentials involved in face recognition and face processing were elicited. The event-related EEG thus displayed an increased signal-to-noise ratio, which facilitated the detection of ERPs extremely well. Consequently, BCI performance was significantly increased. (4) The good results of this new face-flashing paradigm achieved with healthy participants transferred well to users with neurodegenerative disease. Using a face paradigm boosted information throughput. Importantly, two users who were highly inefficient with the commonly used paradigm displayed high accuracy when exposed to the face paradigm. The increased signal-to-noise ratio of the recorded EEG thus helped them to overcome their BCI inefficiency. Significance: The presented work at hand (1) successfully identified a physiological predictor of ERP-BCI performance, (2) proved the technology ready to be operated by na{\"i}ve nonprofessionals without expert support, (3) significantly improved the commonly used spelling paradigm and (4) thereby displayed a way to effectively prevent BCI inefficiency in patients with neurodegenerative disease. Additionally, missing software solutions for appropriate handling of artifacts in heartbeat data encouraged development of our own software tool that is available to the research community free of charge. In sum, this thesis significantly improved current BCI technology and enhanced our understanding of physiological correlates of BCI performance.},
  subject      = {Gehirn-Computer-Schnittstelle},
  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}
}
@phdthesis{Fecher2018,
  author    = {Fecher, Anna},
  title     = {Somatosensibel evozierte Potentiale des Nervus vagus und die Herzratenvariabilit{\"a}t - Physiologischer Zusammenhang und Ver{\"a}nderungen im Rahmen des Mild Cognitive Impairment},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171655},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2018},
  abstract  = {Theoretischer Hintergrund: Im Zuge der aktuellen demographischen Entwicklung konnte in den letzten Dekaden eine extreme Pr{\"a}valenzzunahme der Demenz vom Alzheimertyp (AD) verzeichnet werden, die insbesondere k{\"u}nftige Generationen vor enorme gesundheitspolitische Herausforderungen stellen wird und zur Entwicklung fr{\"u}herer diagnostischer wie auch effektiver therapeutischer Verfahren dr{\"a}ngt. Derzeit verf{\"u}gbare Biomarker der AD sind entweder zu unspezifisch, invasiv oder zu teuer, um sie als breite Screeningwerkzeuge einsetzen zu k{\"o}nnen. Insbesondere die Erkenntnis, dass die pathologischen Prozesse der AD lange vor ihrer klinischen Manifestation im unteren Hirnstamm beginnen, f{\"u}hrte zu der Entwicklung der neuen Methode der somatosensibel evozierten Potentiale des N. vagus (VSEP), die zunehmend als Marker der vagalen Hirnstammfunktion angesehen wird. Dennoch wurde in letzter Zeit die Aussagekraft der Vaguspotentiale angezweifelt, nachdem eine neuere Studie ihren muskul{\"a}ren Ursprung postulierte. Zur Validierung der parasympathischen {\"A}tiologie der VSEP schien die Herzratenvariabilit{\"a}t (HRV) als breit anerkannter Marker der parasympathischen Aktivit{\"a}t besonders geeignet. Beide Methoden wurden auf ihren Zusammenhang sowie auf eine potentielle Ver{\"a}nderung im Rahmen eines „mild cognitive impairment" (MCI) untersucht, um ihr diagnostisches Potenzial bez{\"u}glich eines pr{\"a}dementiellen Stadiums der AD zu {\"u}berpr{\"u}fen. Methoden: Die vorliegende Studie erfolgte als Querschnittsanalyse des ersten Untersuchungszeitpunktes der Vogel-Studie. Nach Ausschluss von Probanden mit HRV- wie VSEP-relevanten Erkrankungen (nicht Hypertonie, Medikamente) und sorgf{\"a}ltiger Datenbearbeitung enthielt die Gesamtstichprobe 218 {\"a}ltere Probanden im Alter von 74 ± 1.4 Jahren (MCI: n=27; kognitiv gesunde Kontrollen: n=191). Die Erhebung der VSEP erfolgte nach den g{\"a}ngigen Methoden von Fallgatter et al. (2003) an den Elektrodenpositionen Fz-F3, Fz-F4, C3-F3, C4-F4 und T4-O1/T3-O1 bei sukzessiver Stimulation beider Innenseiten des Tragus, die Messung der HRV {\"u}ber 15 min mit einem Finometer® Midi. Nur VSEP-Latenzen (P1, N1, P2) und die vagal modulierten HRV-Variablen RMSSD, LF, HF, RSAnorm (nat{\"u}rlicher Logarithmus) wurden in die weitere Analyse eingeschlossen. Zur Gegen{\"u}berstellung von VSEP und HRV in der Kontrollgruppe wurden Korrelationen sowie univariate Varianzanlysen der Quartilgruppen HRV-korrelierter VSEP-Latenzen, zum Vergleich von VSEP und HRV in MCI- und Kontrollgruppe T-Tests f{\"u}r unabh{\"a}ngige Stichproben durchgef{\"u}hrt. Ergebnisse: F{\"u}r die gesunde Kontrollgruppe konnten in den Korrelationsberechnungen unter Kontrolle potentieller Einflussfaktoren signifikante Ergebnisse in den Elektrodenpositionen T4-O2 (Stimulation rechts) sowie C4-F4 (Stimulation links) verzeichnet werden. Alle Latenzkomponenten des Kanals C4-F4 zeigten signifikante, negative Korrelationen mit den vagal modulierten HRV-Parametern (P1 mit ln RMSSD, ln LF, ln HF, RSAnorm; N1 mit ln RMSSD, ln LF, ln HF; P2 mit ln LF). Die jeweiligen Latenz-Quartilgruppenvergleiche best{\"a}tigten, dass l{\"a}ngere P1-Latenzen mit einem signifikant geringeren parasympathischen Tonus (RSAnorm, Trend bei HF) und einer signifikant geringeren Funktion der Baroreflexe (LF) einhergeht, wobei letzteres auch f{\"u}r P2 gilt. Die Ergebnisse der VSEP im Kanal T4-O2 fielen zwar kontr{\"a}r aus (positive Korrelation von P2 mit ln LF, ln HF, ln RSAnorm), konnten jedoch auch in Anbetracht eines allgemein schw{\"a}cheren Zusammenhanges zwischen VSEP und HRV nur unzureichend durch die Varianzanalysen untermauert werden. Die Mittelwertsvergleiche zwischen MCI- und Kontrollgruppe ergaben einerseits vergleichbare HRV-Werte in beiden Gruppen, andererseits eine signifikante P2-Latenzverl{\"a}ngerung im Kanal T4-O2 (Stimulation rechts) in der MCI-Gruppe im Vergleich zu kognitiv gesunden Kontrollen. Schlussfolgerung: Trotz nicht hundertprozentig kongruenter Ergebnisse konnte unter anderem anhand der P1-Latenz im Kanal C4-F4 und der in hohem Maße parasympathisch modulierten RSAnorm ein sehr signifikanter Zusammenhang zwischen HRV und VSEP-Latenzen deutlich gemacht werden. Dies legt den Ursprung der VSEP in den autonomen Strukturen des Hirnstamms nahe. So k{\"o}nnte sich eventuell eine Verz{\"o}gerung der VSEP-Latenz P2, wie es in der vorliegenden Studie bei MCI-Patienten beobachtet wurde, als additiver, nicht-invasiver Biomarker zur Fr{\"u}hdiagnose von pr{\"a}dementiellen Phasen der AD etablieren. Bereits angelaufene L{\"a}ngsschnittstudien wie die Vogelstudie werden k{\"u}nftig genauere Aussagen {\"u}ber die pr{\"a}diktive Aussagekraft der VSEP zur Vorhersage einer AD liefern.},
  subject      = {Vagus},
  language  = {de}
}