303 research outputs found
Iterative two-dimensional signal warping-towards a generalized approach for adaption of one-dimensional signals
No full textAbstract not availableMartin Schmidt, Mathias Baumert, Hagen Malberg, Sebastian Zaunsede
Conventional QT variability measurement vs. template matching techniques: comparison of performance using simulated and real ECG
No full textIncreased beat-to-beat variability in the QT interval (QTV) of ECG has been associated with increased risk for sudden cardiac death, but its measurement is technically challenging and currently not standardized. The aim of this study was to investigate the performance of commonly used beat-to-beat QT interval measurement algorithms. Three different methods (conventional, template stretching and template time shifting) were subjected to simulated data featuring typical ECG recording issues (broadband noise, baseline wander, amplitude modulation) and real short-term ECG of patients before and after infusion of sotalol, a QT interval prolonging drug. Among the three algorithms, the conventional algorithm was most susceptible to noise whereas the template time shifting algorithm showed superior overall performance on simulated and real ECG. None of the algorithms was able to detect increased beat-to-beat QT interval variability after sotalol infusion despite marked prolongation of the average QT interval. The QTV estimates of all three algorithms were inversely correlated with the amplitude of the T wave. In conclusion, template matching algorithms, in particular the time shifting algorithm, are recommended for beat-to-beat variability measurement of QT interval in body surface ECG. Recording noise, T wave amplitude and the beat-rejection strategy are important factors of QTV measurement and require further investigation.Mathias Baumert, Vito Starc and Alberto Port
Two-dimensional warping for one-dimensional signals - conceptual framework and application to ECG processing
No full textWe propose a novel method for evaluating the similarity between two 1d patterns. Our method, referred to as two-dimensional signal warping (2DSW), extends the basic ideas of known warping techniques such as dynamic time warping and correlation optimized warping. By employing two-dimensional piecewise stretching 2DSW is able to take into account inhomogeneous variations of shapes. We apply 2DSW to ECG recordings to extract beat-to-beat variability in QT intervals (QTV) that is indicative of ventricular repolarization lability and typically characterised by a low signal-to-noise ratio. Simulation studies show high robustness of our approach in presence of typical ECG artefacts. Comparison of short-term ECG recorded in normal subjects versus patients with myocardial infarction (MI) shows significantly increased QTV in patients (normal subject 2.36 ms ± 1.05 ms vs. MI patients 5.94 ms ± 5.23 ms (mean ± std), p < 0.001 ). Evaluation of a standard QT database shows that 2DSW allows highly accurate tracking of QRS-onset and T-end. In conclusion, the two-dimensional warping approach introduced here is able to detect subtle changes in noisy quasi-periodic biomedical signals such as ECG and may have diagnostic potential for measuring repolarization lability in MI patients. In more general terms, the proposed method provides a novel means for morphological characterization of 1d signals.Martin Schmidt, Mathias Baumert, Alberto Porta, Hagen Malberg, and Sebastian Zaunsede
Assessment and interpretation of sleep disordered breathing severity in cardiology: clinical implications and perspectives
No full textAbstract not availableDominik Linz, Mathias Baumert, Peter Catcheside, John Floras, Prashanthan Sanders, Patrick Lévy, Martin R.Cowie, R.Doug McEvo
Characterisation of cyclic alternating pattern during sleep in older men and women using large population studies
No full textTo assess the microstructural architecture of non-rapid eye movement (NREM) sleep known as cyclic alternating pattern (CAP) in relation to the age, gender, subjective sleep quality and the degree of sleep disruption in large community-based cohort studies of older people
Cyclic alternating pattern in children with obstructive sleep apnea and its relationship with adenotonsillectomy, behavior, cognition, and quality of life
No full textStudy Objectives: To determine in children with obstructive sleep apnea (OSA) the effect of adenotonsillectomy (AT) on the cyclic alternating pattern (CAP) and the relationship between CAP and behavioral, cognitive, and quality-of-life measures.
Methods: CAP parameters were analyzed in 365 overnight polysomnographic recordings of children with mild-to-moderate OSA enrolled in the Childhood Adenotonsillectomy Trial (CHAT), randomized to either early AT (eAT) or watchful waiting with supportive care (WWSC). We also analyzed CAP in a subgroup of 72 children with moderate OSA (apnea–hypopnea index > 10) that were part of the CHAT sample. Causal mediation analysis was performed to determine the independent effect of changes in CAP on selected outcome measures.
Results: At baseline, a higher number of A1 phases per hour of sleep was significantly associated with worse behavioral functioning (caregiver Behavior Rating Inventory of Executive Function (BRIEF) Global Executive Composite (GEC): ρ = 0.24, p = 0.042; caregiver Conners’ Rating Scale Global Index: ρ = 0.25, p = 0.036) and lower quality of life (OSA-18: ρ = 0.27, p = 0.022; PedsQL: ρ = −0.29, p = 0.015) in the subgroup of children with moderate OSA, but not across the entire sample. At 7-months follow-up, changes in CAP parameters were comparable between the eAT and WWSC arms. CAP changes did not account for significant proportions of variations in behavioral, cognitive, and quality-of-life performance measures at follow-up.
Conclusions: We show a significant association between the frequency of slow, high-amplitude waves with behavioral functioning, as well as the quality of life in children with moderate OSA. Early AT in children with mild-to-moderate OSA does not alter the microstructure of nonrapid eye movement sleep compared with watchful waiting after an approximately 7-month period of follow-up
Delayed brachial artery dilation response and increased resting blood flow velocity in young children with mild sleep-disordered breathing
No full textAbstract not availableAnna Kontos, Cameron van den Heuvel, Yvonne Pamula, James Martin, Kurt Lushington, Mathias Baumert, Scott Willoughby, Roger Gent, Jenny Couper, Declan Kenned
A network physiology approach to the assessment of the link between sinoatrial and ventricular cardiac controls
No full textObjective: A network physiology approach to evaluate the strength of the directed interactions among cardiac controls at sinoatrial and ventricular levels and respiration (R) is proposed. Approach: The network is composed of three nodes (i.e. sinoatrial and ventricular cardiac controls and R) and their activity is exemplified by the variability of heart period (HP), the variability of the duration of the electrical activity of the heart approximated as the temporal distance between Q-wave onset and T-wave end or apex (i.e. QTe or QTa) and thoracic movements respectively. Model-based transfer entropy provided the estimate of the strength of the causal link from the source to the destination conditioned on the remaining node activity. The interactions were monitored in 15 healthy subjects aged from 24 to 54 years (9 males). Increasing levels of sympathetic activity were induced by graded head-up tilt with table inclination of 0, 15, 30, 45, 60, 75°. Main results: We found that: (i) the strength of the causal link from HP to QTe gradually decreases with tilt table angle, while that in the reverse direction is weak, even though significant, and constant; (ii) the action of R on HP is stronger than that from R to QTe; (iii) the strength of the relation from R to HP is weakly related to tilt table inclination, while that from R to QTe does not depend on it; (iv) while QTe cannot affect R, a weak causal dependence of R on HP is detected; (v) the network computed over QTa is qualitatively similar to that over QTe, even though the strength of the causal relations might be different. Significance: The proposed network physiology approach provides a comprehensive picture of the directed links among relevant cardiac regulatory mechanisms and their evolution with sympathetic tone usable to identify pathological conditions.Alberto Porta, Vlasta Bari, Beatrice De Maria and Mathias Baumer
Association between psychotropic medication and sleep microstructure: evidence from large population studies
No full textStudy objectives: To assess the association between psychotropic medications and sleep microstructure in large community-based cohorts of older people. Methods: We analyzed overnight polysomnograms of 381 women from the Study of Osteoporotic Fractures (SOF) and 2,657 men from the Osteoporotic Fractures in Men Sleep Study (MrOS), who either used no psychotropic medication (n=2,819), only benzodiazepines (n=112), or only selective serotonin reuptake inhibitors (SSRI) (n=107). Sleep microstructure (cyclic alternating pattern, CAP) was compared between the no medication group and psychotropic medication groups using the Mann-Whitney U-test. Significant differences were investigated using multivariable linear regression adjusted for confounders. Results: CAP rate, arousal index, apnea-hypopnea index, and the frequency of slow, low-amplitude electroencephalography activation phases were significantly lower in MrOS participants using benzodiazepines than participants not taking psychotropic medication. SSRI users in MrOS experienced no altered sleep microstructure compared to those with no psychotropic use. SOF participants using benzodiazepines did not show similar associations with sleep microstructure. However, SSRI users from SOF had a significantly higher frequency of rapid, high-amplitude electroencephalography activation phases (A2 + 3) and periodic limb-movement index than participants not taking psychotropic medication. Multivariable linear regression adjusted for demographic, lifestyle, mood disorders, and health variables indicated additional significant associations between CAP rate and A2 + 3 index, respectively, and benzodiazepine usage in older men, and between CAP rate and SSRI usage in older women. Conclusions: We identified significant associations between sleep microstructure and psychotropic drugs in MrOS and SOF highlighting the importance of comprehensive sleep analysis, including CAP. Our results may help to better understand the differences in sleep-wake mechanisms based on psychotropic usage. Clinical trial registration: Registry: ClinicalTrials.gov; Title: Outcomes of Sleep Disorders in Older Men; Identifier: NCT00070681; URL: https://clinicaltrials.gov/ct2/show/record/NCT00070681
Brain fog in postural tachycardia syndrome: An objective cerebral blood flow and neurocognitive analysis
No full textFirst published: 03 March 2020Background: It remains unclear whether brain fog is related to impaired cerebral blood flow (CBF) in postural tachycardia syndrome (POTS) patients. Methods: We assessed CBF in the posterior cerebral artery (PCA) using transcranial Doppler with visual stimuli in 11 POTS and 8 healthy subjects in the seated position, followed by neurocognitive testing. Results: CBF parameters were similar between the two groups. POTS patients demonstrated significantly longer latency in delayed match to sample response time and greater errors in attention switching task. Conclusions: Impaired short-term memory and alertness may underlie the symptom of brain fog in POTS patients, despite normal CBF.Rachel Wells, Felix Paterson, Stephen Bacchi, Amanda Page, Mathias Baumert, Dennis H. La
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