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4. Data-based modeling of cerebral hemodynamics quantifies impairment of cerebral blood flow regulation in type-2 diabetes.

Author

Marmarelis, Vasilis Z, Shin, Dae C, Kang, Yue, and Novak, Vera

Abstract

We studied the regulation dynamics of cerebral blood velocity (CBv) at middle cerebral arteries (MCA) in response to spontaneous changes of arterial blood pressure (ABP), termed dynamic cerebral autoregulation (dCA), and end-tidal CO2 as proxy for blood CO2 tension, termed dynamic vasomotor reactivity (DVR), by analyzing time-series data collected at supine rest from 36 patients with Type-2 Diabetes Mellitus (T2DM) and 22 age/sex-matched non-diabetic controls without arterial hypertension. Our analysis employed a robust dynamic modeling methodology that utilizes Principal Dynamic Modes (PDM) to estimate subject-specific dynamic transformations of spontaneous changes in ABP and end-tidal CO2 (viewed as two "inputs") into changes of CBv at MCA measured via Transcranial Doppler ultrasound (viewed as the "output"). The quantitative results of PDM analysis indicate significant alterations in T2DM of both DVR and dCA in terms of two specific PDM contributions that rise to significance (p < 0.05). Our results further suggest that the observed DVR and dCA alterations may be due to reduction of cholinergic activity (based on previously published results from cholinergic blockade data) that may disturb the sympatho-vagal balance in T2DM. Combination of these two model-based "physio-markers" differentiated T2DM patients from controls (p = 0.0007), indicating diabetes-related alteration of cerebrovascular regulation, with possible diagnostic implications. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Cross-Correlation of Instantaneous Phase Increments in Pressure-Flow Fluctuations: Applications to Cerebral Autoregulation

Author

Chen, Zhi, Hu, Kun, Stanley, H. Eugene, Novak, Vera, and Ivanov, Plamen Ch.

Subjects
Physics - Biological Physics, Condensed Matter - Soft Condensed Matter
Abstract

We investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during the quasi-steady state after perturbation for four different physiologic conditions: supine rest, head-up tilt, hyperventilation and CO_2 rebreathing in upright position. To evaluate whether instantaneous BP changes in the steady state are coupled with instantaneous changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well pronounced patterns that remain stable in time for all four conditions, while in healthy subjects these patterns are different, less pronounced and more variable. We propose a new approach based on the instantaneous phase increments cross-correlation to quantify the coupling between BP and BFV. We find that the maximum correlation strength is different for the two groups and for the different conditions. For healthy subjects the amplitude of the cross-correlation between the instantaneous phase increments of BP and BFV is small and attenuates within 3-5 heartbeats. In contrast, for post-stroke subjects, this amplitude is significantly larger and cross-correlations persist up to 20 heartbeats. We compare the results of our approach with three complementary methods: direct BP-BFV cross-correlation, transfer function analysis and phase synchronization analysis., Comment: 15 pages, 6 figures; extensively expanded the manuscript including new analyses and results presented in 3 new figures, added more references

Published
2005
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16. Basic Study Designs

Author

Gomez, Alexandra, additional, Fregni, Felipe, additional, Novak, Vera, additional, and Brunoni, Andre, additional

Published
2018
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21. Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure–flow relation: The CARNet study

Author

Meel-van den Abeelen, Aisha S.S., Simpson, David M., Wang, Lotte J.Y., Slump, Cornelis H., Zhang, Rong, Tarumi, Takashi, Rickards, Caroline A., Payne, Stephen, Mitsis, Georgios D., Kostoglou, Kyriaki, Marmarelis, Vasilis, Shin, Dae, Tzeng, Yu-Chieh, Ainslie, Philip N., Gommer, Erik, Müller, Martin, Dorado, Alexander C., Smielewski, Peter, Yelicich, Bernardo, Puppo, Corina, Liu, Xiuyun, Czosnyka, Marek, Wang, Cheng-Yen, Novak, Vera, Panerai, Ronney B., and Claassen, Jurgen A.H.R.

Published
2014
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37. Enhancement of vasoreactivity and cognition by intranasal insulin in type 2 diabetes

Author

Novak, Vera, Milberg, William, Hao, Ying, Munshi, Medha, Novak, Peter, Galica, Andrew, Manor, Bradley, Roberson, Paula, Craft, Suzanne, and Abduljalil, Amir

Subjects
Blood vessels -- Research -- Analysis -- Physiological aspects, Cognition -- Research -- Analysis, Insulin -- Research -- Usage, Health
Abstract

OBJECTIVE To determine acute effects of intranasal insulin on regional cerebral perfusion and cognition in older adults with type 2 diabetes mellitus (DM). RESEARCH DESIGN AND METHODS This was a [...]

Published
2014
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40. sj-docx-1-tan-10.1177_17562864211045876 – Supplemental material for Glycemic variability of acute stroke patients and clinical outcomes: a continuous glucose monitoring study

Author

Palaiodimou, Lina, Lioutas, Vasileios-Arsenios, Lambadiari, Vaia, Theodorou, Aikaterini, Themistocleous, Marios, Aponte, Laura, Papagiannopoulou, Georgia, Foska, Aikaterini, Bakola, Eleni, Quispe, Rodrigo, Mendez, Laura, Selim, Magdy, Novak, Vera, Tzavellas, Elias, Halvatsiotis, Panagiotis, Voumvourakis, Konstantinos, and Tsivgoulis, Georgios

Subjects
FOS: Clinical medicine, 111599 Pharmacology and Pharmaceutical Sciences not elsewhere classified, 110904 Neurology and Neuromuscular Diseases
Abstract

Supplemental material, sj-docx-1-tan-10.1177_17562864211045876 for Glycemic variability of acute stroke patients and clinical outcomes: a continuous glucose monitoring study by Lina Palaiodimou, Vasileios-Arsenios Lioutas, Vaia Lambadiari, Aikaterini Theodorou, Marios Themistocleous, Laura Aponte, Georgia Papagiannopoulou, Aikaterini Foska, Eleni Bakola, Rodrigo Quispe, Laura Mendez, Magdy Selim, Vera Novak, Elias Tzavellas, Panagiotis Halvatsiotis, Konstantinos Voumvourakis and Georgios Tsivgoulis in Therapeutic Advances in Neurological Disorders

Published
2021
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49. Cardiolocomotor coupling in young and elderly people

Author

Novak, Vera, Hu, Kun, Vyas, Mitul, and Lipsitz, Lewis A.

Subjects
Cardiovascular system -- Demographic aspects, Cardiopulmonary system -- Demographic aspects, Nervous system, Autonomic -- Demographic aspects, Human locomotion -- Demographic aspects, Aging -- Influence, Aging -- Psychological aspects, Aging -- Health aspects, Health, Seniors
Abstract

Background. Walking is a complex act that requires the coordination of locomotor, cardiovascular, and autonomic systems. Aging affects each of these systems and may alter physiological mechanisms regulating the interactions between them. Methods. We examined the effects of healthy aging on cardiac-locomotor coupling using treadmill walking at incremental speeds from 0.8 mph to normal walking speed in 12 healthy young (29.0 [+ or -] 5.0 years) and 9 healthy elderly persons (70.3 [+ or -] 5.1 years), interbeat (R-R) intervals, step intervals, maximum foot pressure (MFP) and normalized maximum force, blood pressure (BP), and blood flow velocity (BFV) in the middle cerebral artery were continuously measured. Results. Step intervals and R-R intervals decreased, and MFP and BFV increased with walking speed in both groups; systolic BP increased (p < .0001) in the old group. In elderly, but not in young participants, step intervals and R-R intervals were coupled ([R.sup.2] = 0.84, p < .0001), and MFP was correlated with systolic BP ([R.sup.2] = 0.51, p < .02). Conclusion. Cardiolocomotor coupling that becomes manifest with aging may optimize cardiovascular responses during walking. In elderly people, forces generated during the gait cycle may be transmitted to arterial pressure and thus synchronize the central cardiovascular network with the stepping rhythm.

Published
2007

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