1
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Webb AJ, Klerman EB, Mandeville ET. Circadian and Diurnal Regulation of Cerebral Blood Flow. Circ Res 2024; 134:695-710. [PMID: 38484025 PMCID: PMC10942227 DOI: 10.1161/circresaha.123.323049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/30/2024] [Accepted: 02/07/2024] [Indexed: 03/17/2024]
Abstract
Circadian and diurnal variation in cerebral blood flow directly contributes to the diurnal variation in the risk of stroke, either through factors that trigger stroke or due to impaired compensatory mechanisms. Cerebral blood flow results from the integration of systemic hemodynamics, including heart rate, cardiac output, and blood pressure, with cerebrovascular regulatory mechanisms, including cerebrovascular reactivity, autoregulation, and neurovascular coupling. We review the evidence for the circadian and diurnal variation in each of these mechanisms and their integration, from the detailed evidence for mechanisms underlying the nocturnal nadir and morning surge in blood pressure to identifying limited available evidence for circadian and diurnal variation in cerebrovascular compensatory mechanisms. We, thus, identify key systemic hemodynamic factors related to the diurnal variation in the risk of stroke but particularly identify the need for further research focused on cerebrovascular regulatory mechanisms.
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Affiliation(s)
- Alastair J.S. Webb
- Department of Clinical Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford, United Kingdom (A.J.S.W.)
| | - Elizabeth B. Klerman
- Department of Clinical Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford, United Kingdom (A.J.S.W.)
- Department of Neurology, Massachusetts General Hospital, Boston (E.B.K.)
- Division of Sleep and Circadian Disorders, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (E.B.K.)
- Division of Sleep Medicine, Harvard Medical School, Boston, MA (E.B.K.)
| | - Emiri T. Mandeville
- Departments of Radiology and Neurology, Neuroprotection Research Laboratories, Massachusetts General Hospital, Harvard Medical School, Boston (E.T.M.)
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2
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Abadjiev DS, Toschi-Dias E, Salinet ASM, Gaykova NN, Lo MT, Nogueira RC, Hu K. Daily rhythm of dynamic cerebral autoregulation in patients after stroke. J Cereb Blood Flow Metab 2023; 43:989-998. [PMID: 36722135 PMCID: PMC10196745 DOI: 10.1177/0271678x231153750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 12/02/2022] [Accepted: 01/02/2022] [Indexed: 02/02/2023]
Abstract
Dynamic cerebral autoregulation (dCA) in healthy young adults displays a daily variation. Whether the rhythm exists in patients with stroke is unknown. We studied 28 stroke patients (age: 26-83 years, 7 females) within 48 hours after thrombolysis. dCA was assessed 54 times in these patients during supine rest (twice in 26 and once in 2 patients): 9 assessments between 0-9AM, 12 between 9AM-2PM, 20 between 2-7PM, and 13 between 7PM-12AM. To estimate dCA, phase shifts between spontaneous oscillations of cerebral blood flow velocity (CBFV) in the middle cerebral artery and arterial blood pressure (BP) were obtained in four frequency bands: <0.05 Hz, 0.05-0.1 Hz, 0.1-0.2 Hz, and >0.2 Hz. CBFV-BP phase shifts at <0.05 Hz were significantly larger between 2-7PM, suggesting better dCA, than those at other times (p < 0.0001), and the daily rhythm was consistent for stroke and non-stroke sides. No significant rhythms were observed at higher frequencies (all p > 0.2). All results were independent of age, sex, stroke type and severity, and other cardiovascular conditions. dCA after stroke showed a daily rhythm, leading to a better regulation of CBFV at <0.05 Hz during the afternoon. The finding may have implications for daily activity management of stroke patients.
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Affiliation(s)
- Daniel S Abadjiev
- Medical Biodynamics Program,
Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Harvard
Medical School, Boston, MA, USA
| | - Edgar Toschi-Dias
- Neurology Department, School of
Medicine, Hospital das Clinicas, University of São Paulo, São Paulo ,
Brazil
| | - Angela SM Salinet
- Neurology Department, School of
Medicine, Hospital das Clinicas, University of São Paulo, São Paulo ,
Brazil
| | - Nicole N Gaykova
- Medical Biodynamics Program,
Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Harvard
Medical School, Boston, MA, USA
| | - Men-Tzung Lo
- Institute of Translational and
Interdisciplinary Medicine and Department of Biomedical Sciences and
Engineering, National Central University, Taoyuan
| | - Ricardo C Nogueira
- Neurology Department, School of
Medicine, Hospital das Clinicas, University of São Paulo, São Paulo ,
Brazil
- Neurology Department, Hospital
Sirio Libanes, São Paulo, Brazil
| | - Kun Hu
- Medical Biodynamics Program,
Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Harvard
Medical School, Boston, MA, USA
- Division of Sleep Medicine, Harvard
Medical School, Boston, MA, USA
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3
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Shariffi B, Lloyd IN, Cessac ME, Harper JL, Limberg JK. Reproducibility and diurnal variation in middle cerebral artery blood velocity in healthy humans. Exp Physiol 2023; 108:692-705. [PMID: 36951536 PMCID: PMC10148902 DOI: 10.1113/ep090873] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 03/02/2023] [Indexed: 03/24/2023]
Abstract
NEW FINDINGS What is the central question of this study? We sought to establish between-day reproducibility in estimates of middle cerebral artery blood velocity (MCAv) and cerebrovascular reactivity (CVR) in young, healthy male and female adults in tightly controlled experimental conditions. What is the main finding and its importance? Measures of MCAv assessed during morning, afternoon and evening hours are reproducible between days. There is diurnal variation in CVR, with values being highest during the evening compared with the morning. Greater diurnal variation in CVR is associated with more efficient sleep and greater nocturnal blood pressure dipping. These data enhance our understanding of modulators of MCAv and CVR. ABSTRACT Transcranial Doppler (TCD) is used to assess cerebral blood velocity (CBV) and cerebrovascular reactivity (CVR). Assessments of TCD reproducibility are limited, and few include multiple within-day measurements. We sought to establish reproducibility of CBV and CVR in healthy adults during three time periods (morning, afternoon and evening). We hypothesized that CBV and CVR measured at the same time of day are reproducible between days. We also hypothesized that CBV and CVR exhibit diurnal variation, with measurements being higher in the evening compared with morning/afternoon hours. Twelve adults [six male and six female, 27 years (95% CI, 22-31 years)] completed three measurements (morning, afternoon and evening) on two separate days in controlled conditions (e.g., meals, activity and sleep). Middle cerebral artery blood velocity (MCAv, TCD) was measured continuously at rest and during two CVR tests (end-expiratory apnoea and carbogen inhalation). Intraclass correlation coefficients for resting MCAv showed moderate to good reproducibility, which did not differ between morning, afternoon and evening (0.87, 0.56 and 0.67, respectively; P > 0.05). Intraclass correlation coefficients for peak MCAv during apnoea (0.80, 0.46 and 0.65, respectively; P > 0.05) and minute 2 of carbogen inhalation (0.81, 0.74 and 0.73, respectively; P > 0.05) were also not different from morning compared with afternoon/evening. Time of day had no effect on resting MCAv (F = 0.69, P = 0.51, ƞp 2 = 0.06) or the peak response to apnoea (F = 1.00, P = 0.39, ƞp 2 = 0.08); however, peak MCAv during carbogen breathing exhibited diurnal variation, with highest values in the evening (F = 3.41, P = 0.05, ƞp 2 = 0.24). Measures of CBV and CVR assessed via TCD during morning, afternoon and evening hours are reproducible between days. There is diurnal variation in the MCAv response to carbogen exposure, with CVR being highest during evening compared with morning hours.
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Affiliation(s)
- Brian Shariffi
- Department of Nutrition and Exercise PhysiologyUniversity of MissouriColumbiaMissouriUSA
| | - Iman N. Lloyd
- Department of Nutrition and Exercise PhysiologyUniversity of MissouriColumbiaMissouriUSA
| | - Mikala E. Cessac
- Department of Nutrition and Exercise PhysiologyUniversity of MissouriColumbiaMissouriUSA
| | - Jennifer L. Harper
- Department of Nutrition and Exercise PhysiologyUniversity of MissouriColumbiaMissouriUSA
| | - Jacqueline K. Limberg
- Department of Nutrition and Exercise PhysiologyUniversity of MissouriColumbiaMissouriUSA
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Orban C, Kong R, Li J, Chee MWL, Yeo BTT. Time of day is associated with paradoxical reductions in global signal fluctuation and functional connectivity. PLoS Biol 2020; 18:e3000602. [PMID: 32069275 PMCID: PMC7028250 DOI: 10.1371/journal.pbio.3000602] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 01/15/2020] [Indexed: 12/13/2022] Open
Abstract
The brain exhibits substantial diurnal variation in physiology and function, but neuroscience studies rarely report or consider the effects of time of day. Here, we examined variation in resting-state functional MRI (fMRI) in around 900 individuals scanned between 8 AM and 10 PM on two different days. Multiple studies across animals and humans have demonstrated that the brain’s global signal (GS) amplitude (henceforth referred to as “fluctuation”) increases with decreased arousal. Thus, in accord with known circadian variation in arousal, we hypothesised that GS fluctuation would be lowest in the morning, increase in the midafternoon, and dip in the early evening. Instead, we observed a cumulative decrease in GS fluctuation as the day progressed. Although respiratory variation also decreased with time of day, control analyses suggested that this did not account for the reduction in GS fluctuation. Finally, time of day was associated with marked decreases in resting-state functional connectivity across the whole brain. The magnitude of decrease was significantly stronger than associations between functional connectivity and behaviour (e.g., fluid intelligence). These findings reveal time of day effects on global brain activity that are not easily explained by expected arousal state or physiological artefacts. We conclude by discussing potential mechanisms for the observed diurnal variation in resting brain activity and the importance of accounting for time of day in future studies. The brain exhibits substantial diurnal variation in physiology and function. A large-scale fMRI study reveals that the brain’s global signal amplitude, typically elevated during drowsy states, unexpectedly reduces steadily as the day progresses.
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Affiliation(s)
- Csaba Orban
- Department of Electrical and Computer Engineering, N.1 Institute for Health and Memory Networks Program, National University of Singapore, Singapore
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Clinical Imaging and Research Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Neuropsychopharmacology Unit, Centre for Psychiatry, Imperial College London, London, United Kingdom
- * E-mail: (CO); (BTTY)
| | - Ru Kong
- Department of Electrical and Computer Engineering, N.1 Institute for Health and Memory Networks Program, National University of Singapore, Singapore
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Clinical Imaging and Research Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Jingwei Li
- Department of Electrical and Computer Engineering, N.1 Institute for Health and Memory Networks Program, National University of Singapore, Singapore
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Clinical Imaging and Research Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michael W. L. Chee
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Clinical Imaging and Research Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
| | - B. T. Thomas Yeo
- Department of Electrical and Computer Engineering, N.1 Institute for Health and Memory Networks Program, National University of Singapore, Singapore
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Clinical Imaging and Research Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
- * E-mail: (CO); (BTTY)
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5
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Sperna Weiland NH, Hermanides J, Hollmann MW, Preckel B, Stok WJ, van Lieshout JJ, Immink RV. Novel method for intraoperative assessment of cerebral autoregulation by paced breathing. Br J Anaesth 2019; 119:1141-1149. [PMID: 29028933 DOI: 10.1093/bja/aex333] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2017] [Indexed: 11/14/2022] Open
Abstract
Background Cerebral autoregulation (CA) is the mechanism that maintains constancy of cerebral blood flow (CBF) despite variations in blood pressure (BP). Patients with attenuated CA have been shown to have an increased incidence of peri-operative stroke. Studies of CA in anaesthetized subjects are rare, because a simple and non-invasive method to quantify the integrity of CA is not available. In this study, we set out to improve non-invasive quantification of CA during surgery. For this purpose, we introduce a novel method to amplify spontaneous BP fluctuations during surgery by imposing mechanical positive pressure ventilation at three different frequencies and quantify CA from the resulting BP oscillations. Methods Fourteen patients undergoing sevoflurane anaesthesia were included in the study. Continuous non-invasive BP and transcranial Doppler-derived CBF velocity (CBF V ) were obtained before surgery during 3 min of paced breathing at 6, 10, and 15 bpm and during surgery from mechanical positive pressure ventilation at identical frequencies. Data were analysed using frequency domain analysis to obtain CBF V -to-BP phase lead as a continuous measure of CA efficacy. Group averages were calculated. Values are means ( sd ), and P <0.05 was used to indicate statistical significance. Results Preoperative vs intraoperative CBF V -to-BP phase lead was 43 (9) vs 45 (8)°, 25 (8) vs 24 (10)°, and 4 (6) vs -2 (12)° during 6, 10, and 15 bpm, respectively (all P =NS). Conclusions During surgery, cerebral autoregulation indices were similar to values determined before surgery. This indicates that CA can be quantified reliably and non-invasively using this novel method and confirms earlier evidence that CA is unaffected by sevoflurane anaesthesia. Clinical trial registration NCT03071432.
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Affiliation(s)
- N H Sperna Weiland
- Department of Anaesthesiology.,Department of Medical Biology, Laboratory for Clinical Cardiovascular Physiology
| | | | | | | | - W J Stok
- Department of Medical Biology, Laboratory for Clinical Cardiovascular Physiology
| | - J J van Lieshout
- Department of Medical Biology, Laboratory for Clinical Cardiovascular Physiology.,Department of Internal Medicine, Academic Medical Centre AMC Amsterdam, University of Amsterdam, PO Box 22660, 1100DD Amsterdam, The Netherlands.,MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK
| | - R V Immink
- Department of Anaesthesiology.,Department of Medical Biology, Laboratory for Clinical Cardiovascular Physiology
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6
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7
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Ryan CM, Battisti-Charbonney A, Sobczyk O, Mikulis DJ, Duffin J, Fisher JA, Venkatraghavan L. Evaluation of Cerebrovascular Reactivity in Subjects with and without Obstructive Sleep Apnea. J Stroke Cerebrovasc Dis 2018; 27:162-168. [DOI: 10.1016/j.jstrokecerebrovasdis.2017.08.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 08/13/2017] [Indexed: 11/27/2022] Open
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8
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Tsuji B, Honda Y, Kondo N, Nishiyasu T. Diurnal variation in the control of ventilation in response to rising body temperature during exercise in the heat. Am J Physiol Regul Integr Comp Physiol 2016; 311:R401-9. [PMID: 27335282 DOI: 10.1152/ajpregu.00484.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 06/17/2016] [Indexed: 11/22/2022]
Abstract
We investigated whether heat-induced hyperventilation during exercise is affected by time of day, as diurnal variation leads to higher core temperatures in the evening. Nineteen male subjects were divided into two experiments (protocol 1, n = 10 and protocol 2, n = 9). In protocol 1, subjects performed cycle exercise at 50% peak oxygen uptake in the heat (37°C and 50% RH) in the morning (0600) and evening (1800). Results showed that baseline resting and exercising esophageal temperature (Tes) were significantly (0.5°C) higher in the evening than morning. Minute ventilation (V̇e) increased from 54.3 ± 7.9 and 54.9 ± 6.8 l/min at 10 min to 71.4 ± 8.1 and 76.5 ± 11.8 l/min at 48.5 min in the morning and evening, respectively (both P < 0.01). Time of day had no effect on V̇e (P = 0.44). When V̇e as the output response was plotted against Tes as thermal input, the Tes threshold for increases in V̇e was higher in the evening than morning (37.2 ± 0.7 vs. 36.6 ± 0.6°C, P = 0.009), indicating the ventilatory response to the same core temperature is smaller in the evening. In protocol 2, the circadian rhythm-related higher resting Tes seen in the evening was adjusted down to the same temperature seen in the morning by immersing the subject in cold water. Importantly, the time course of changes in V̇e during exercise were smaller in the evening, but the threshold for V̇e remained higher in the evening than morning (P < 0.001). Collectively, those results suggest that time of day has no effect on time course hyperventilation during exercise in the heat, despite the higher core temperatures in the evening. This is likely due to diurnal variation in the control of ventilation in response to rising core temperature.
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Affiliation(s)
- Bun Tsuji
- Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan; Department of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan; and
| | - Yasushi Honda
- Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
| | - Narihiko Kondo
- Faculty of Human Development, Kobe University, Kobe, Japan
| | - Takeshi Nishiyasu
- Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan;
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9
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Ogoh S, Sato K, Okazaki K, Miyamoto T, Hirasawa A, Shibasaki M. Hyperthermia modulates regional differences in cerebral blood flow to changes in CO2. J Appl Physiol (1985) 2014; 117:46-52. [PMID: 24790021 DOI: 10.1152/japplphysiol.01078.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to assess blood flow responses to changes in carbon dioxide (CO2) in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) during normothermic and hyperthermic conditions. Eleven healthy subjects aged 22 ± 2 (SD) yr were exposed to passive whole body heating followed by spontaneous hypocapnic and hypercapnic challenges in normothermic and hyperthermic conditions. Right ICA, ECA, and VA blood flows, as well as left middle cerebral artery (MCA) mean blood velocity (Vmean), were measured. Esophageal temperature was elevated by 1.53 ± 0.09°C before hypocapnic and hypercapnic challenges during heat stress. Whole body heating increased ECA blood flow and cardiac output by 130 ± 78 and 47 ± 26%, respectively (P < 0.001), while blood flow (or velocity) in the ICA, MCA, and VA was reduced by 17 ± 14, 24 ± 18, and 12 ± 7%, respectively (P < 0.001). Regardless of the thermal conditions, ICA and VA blood flows and MCA Vmean were decreased by hypocapnic challenges and increased by hypercapnic challenges. Similar responses in ECA blood flow were observed in hyperthermia but not in normothermia. Heat stress did not alter CO2 reactivity in the MCA and VA. However, CO2 reactivity in the ICA was decreased (3.04 ± 1.17 vs. 2.23 ± 1.03%/mmHg; P = 0.039) but that in the ECA was enhanced (0.45 ± 0.47 vs. 0.95 ± 0.61%/mmHg; P = 0.032). These results indicate that hyperthermia is capable of altering dynamic cerebral blood flow regulation.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Saitama, Japan
| | - Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan
| | - Kazunobu Okazaki
- Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, Osaka, Japan
| | | | - Ai Hirasawa
- Department of Biomedical Engineering, Toyo University, Saitama, Japan
| | - Manabu Shibasaki
- Department of Environmental Health, Nara Women's University, Nara, Japan
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10
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Feigin VL, Wiebers DO. Environmental factors and stroke: A selective review. J Stroke Cerebrovasc Dis 2012; 6:108-13. [PMID: 17894980 DOI: 10.1016/s1052-3057(97)80225-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/1996] [Accepted: 10/10/1996] [Indexed: 10/24/2022] Open
Abstract
Despite numerous prior stroke risk factor investigations, much remains unknown about the effect of environmental factor changes on stroke incidence and mortality rates. Yet these data might be important for defining a number of measures to prevent stroke and for developing a greater understanding of the origin and incidence trends of stroke in different regions and populations. In this paper we review the current state of knowledge about certain environmental stroke risk factors.
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Affiliation(s)
- V L Feigin
- From the University Department of Neurology, Utrecht, the Netherlands
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11
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Peebles KC, Ball OG, MacRae BA, Horsman HM, Tzeng YC. Sympathetic regulation of the human cerebrovascular response to carbon dioxide. J Appl Physiol (1985) 2012; 113:700-6. [DOI: 10.1152/japplphysiol.00614.2012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the cerebrovasculature is known to be exquisitely sensitive to CO2, there is no consensus on whether the sympathetic nervous system plays a role in regulating cerebrovascular responses to changes in arterial CO2. To address this question, we investigated human cerebrovascular CO2 reactivity in healthy participants randomly assigned to the α1-adrenoreceptor blockade group (9 participants; oral prazosin, 0.05 mg/kg) or the placebo control (9 participants) group. We recorded mean arterial blood pressure (MAP), heart rate (HR), mean middle cerebral artery flow velocity (MCAV mean), and partial pressure of end-tidal CO2 (PetCO2) during 5% CO2 inhalation and voluntary hyperventilation. CO2 reactivity was quantified as the slope of the linear relationship between breath-to-breath PetCO2 and the average MCAvmean within successive breathes after accounting for MAP as a covariate. Prazosin did not alter resting HR, PetCO2, MAP, or MCAV mean. The reduction in hypocapnic CO2 reactivity following prazosin (−0.48 ± 0.093 cm·s−1·mmHg−1) was greater compared with placebo (−0.19 ± 0.087 cm·s−1·mmHg−1; P < 0.05 for interaction). In contrast, the change in hypercapnic CO2 reactivity following prazosin (−0.23 cm·s−1·mmHg−1) was similar to placebo (−0.31 cm·s−1·mmHg−1; P = 0.50 for interaction). These data indicate that the sympathetic nervous system contributes to CO2 reactivity via α1-adrenoreceptors; blocking this pathway with prazosin reduces CO2 reactivity to hypocapnia but not hypercapnia.
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Affiliation(s)
- K. C. Peebles
- Cardiovascular Systems Laboratory, Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - O. G. Ball
- Cardiovascular Systems Laboratory, Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - B. A. MacRae
- Cardiovascular Systems Laboratory, Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - H. M. Horsman
- Cardiovascular Systems Laboratory, Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - Y. C. Tzeng
- Cardiovascular Systems Laboratory, Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
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12
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Ivey FM, Ryan AS, Hafer-Macko CE, Macko RF. Improved Cerebral Vasomotor Reactivity After Exercise Training in Hemiparetic Stroke Survivors. Stroke 2011; 42:1994-2000. [DOI: 10.1161/strokeaha.110.607879] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Animal studies provide strong evidence that aerobic exercise training positively influences cerebral blood flow, but no human studies support the use of exercise for improving cerebral hemodynamics. This randomized study in stroke survivors assessed the effects of treadmill aerobic exercise training (TM) on cerebral blood flow parameters compared to a control intervention of nonaerobic stretching.
Methods—
Thirty-eight participants (19 in TM group and 19 in control group) with remote stroke (>6 months) and mild to moderate gait deficits completed middle cerebral artery blood flow velocity measurements by transcranial Doppler ultrasonography before and after a 6-month intervention period. Middle cerebral artery blood flow velocity was assessed bilaterally during normocapnia and hypercapnia (6% CO
2
). Cerebral vasomotor reactivity (cVMR) was calculated as percent change in middle cerebral artery blood flow velocity from normocapnia to hypercapnia (cVMR percent) and as an index correcting percent change for absolute increase in end tidal CO
2
(cVMR index).
Results—
The TM group had significantly larger improvements than did controls for both ipsilesional and contralesional cVMR index (
P
≤0.05) and contralesional cVMR percent (
P
≤0.01). Statin users in the TM group (n=10) had higher baseline cVMR and lower training-induced cVMR change, indicating that cVMR change among those not using statins (n=9) primarily accounted for the between-group effects. There was a 19% increase in V
o
2
peak for the TM group compared to a 4% decrease in the control group (
P
<0.01), and peak fitness change correlated with cVMR change (
r
=0.55;
P
<0.05).
Conclusions—
Our data provide the first evidence to our knowledge of exercise-induced cVMR improvements in stroke survivors, implying a protective mechanism against recurrent stroke and other brain-related disorders. Statin use appears to regulate cVMR and the cVMR training response.
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Affiliation(s)
- Frederick M. Ivey
- From the Departments of Neurology (F.M.I., R.F.M., C.E.H.M.) and Medicine (F.M.I., A.S.R., C.E.H.M., R.F.M.), Division of Gerontology and Geriatric Medicine, Department of Veterans Affairs and Veterans Affairs Medical Center, Geriatric Research, Education, and Clinical Center (GRECC), University of Maryland School of Medicine, Baltimore, MD
| | - Alice S. Ryan
- From the Departments of Neurology (F.M.I., R.F.M., C.E.H.M.) and Medicine (F.M.I., A.S.R., C.E.H.M., R.F.M.), Division of Gerontology and Geriatric Medicine, Department of Veterans Affairs and Veterans Affairs Medical Center, Geriatric Research, Education, and Clinical Center (GRECC), University of Maryland School of Medicine, Baltimore, MD
| | - Charlene E. Hafer-Macko
- From the Departments of Neurology (F.M.I., R.F.M., C.E.H.M.) and Medicine (F.M.I., A.S.R., C.E.H.M., R.F.M.), Division of Gerontology and Geriatric Medicine, Department of Veterans Affairs and Veterans Affairs Medical Center, Geriatric Research, Education, and Clinical Center (GRECC), University of Maryland School of Medicine, Baltimore, MD
| | - Richard F. Macko
- From the Departments of Neurology (F.M.I., R.F.M., C.E.H.M.) and Medicine (F.M.I., A.S.R., C.E.H.M., R.F.M.), Division of Gerontology and Geriatric Medicine, Department of Veterans Affairs and Veterans Affairs Medical Center, Geriatric Research, Education, and Clinical Center (GRECC), University of Maryland School of Medicine, Baltimore, MD
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Hanak V, Somers VK. Cardiovascular and cerebrovascular physiology in sleep. HANDBOOK OF CLINICAL NEUROLOGY 2011; 98:315-25. [PMID: 21056194 DOI: 10.1016/b978-0-444-52006-7.00019-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Viktor Hanak
- Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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14
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Calvo Vecino JM, Abad Gurumeta A, Garrido Reche E, Chao Novo K, Orts Castro A, Tomás Lachos J. [Transcranial Doppler ultrasound, bispectral index, and electroencephalographic monitoring of entropy during pediatric total intravenous anesthesia]. REVISTA ESPANOLA DE ANESTESIOLOGIA Y REANIMACION 2010; 57:621-629. [PMID: 22283014 DOI: 10.1016/s0034-9356(10)70298-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND AND OBJECTIVE Transcranial Doppler ultrasound is a noninvasive technique for monitoring the velocity of blood flow in the main intracranial arteries, particularly those in the circle of Willis. Our aim was to assess whether changes in cerebral arterial blood flow in anesthetized pediatric patients detected by pulsed Doppler ultrasound correlate with changes in the bispectral (BIS) index and electroencephalographic state and response entropy (ES and ER, respectively). MATERIAL AND METHODS Prospective, blinded observational study of 36 pediatric patients (age range, 5 to 11 years) under total intravenous anesthesia for minor surgical procedures. Propofol and fentanyl were used for induction; propofol and remifentanil in continuous perfusion and a single dose of cisatracurium were used for maintenance. In all patients we monitored hemodynamic and respiratory patterns, gases, temperature, and hypnosis (BIS, ES and ER) as well as cerebral blood flow estimated by pulsed Doppler ultrasound in the middle cerebral artery. Raw data were subjected to statistical smoothing. The resistance index, pulsatility index, mean velocity, and estimated baseline cerebral blood flow were calculated from the Doppler sonogram. We then studied the correlations between the Doppler-derived values and BIS, ES, ER, fraction of end-tidal carbon dioxide, and temperature. The variables were entered into logistic regression. RESULTS The pattern at induction indicated high resistance (low mean velocities and high pulsatility indexes) until the lowest BIS and ES values of 31 and 29, respectively, were reached. During maintenance, the Doppler sonogram pattern was slower (normalization of the pulsatility index, the resistance index, and mean velocity). Changes in flow and absolute entropy and BIS values were statistically correlated (Pearson's r values > or = 0.91); there was 95.6% agreement between Doppler values and BIS and agreement between BIS and ES values of 35-45. On awakening, flow velocities approached baseline values when BIS and ES rose to between 90 and 98. The estimated cerebral blood flow underwent fluctuations coinciding with an approximately concomitant increase or decrease in BIS (r > 0.95); the response of BIS was slightly delayed by no more than a minute but there was no corresponding response of entropy measurements. CONCLUSIONS We report Doppler ultrasound patterns during anesthesia with propofol. Systems for monitoring hypnosis could be considered indirect measurements of cerebral blood flow; BIS measurements are more sensitive to flow change. Transcranial Doppler ultrasound facilitates the observation of changes in blood flow that occur at different levels of hypnosis during anesthesia.
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Affiliation(s)
- J M Calvo Vecino
- Servicio de Anestesiología y Reanimación, Complejo Hospitalario de Vallecas, Hospital Infanta Leonor, Vallecas, Madrid.
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15
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El-Mitwalli A, Zaher AA, El Menshawi E. Circadian rhythm of stroke onset during the month of Ramadan. Acta Neurol Scand 2010; 122:97-101. [PMID: 19839942 DOI: 10.1111/j.1600-0404.2009.01265.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND PURPOSE The onset of acute stroke exhibits a circadian pattern occurring more frequently in late morning hours. The objective of this study was to investigate the diurnal pattern of stroke during the month of Ramadan. PATIENTS AND METHODS We studied consecutive stroke patients 1 month before Ramadan (BR) and during Ramadan (DR) over two successive years 2007 and 2008. The age, gender, risk factor profiles were analyzed. The National Institute of Health and Stroke Scale Score (NIHSS) was used for clinical assessment at admission. The exact time of stroke onset in both groups was obtained. RESULTS A total of 507 patients were studied: 245 patients in the DR group and 262 patients in the BR group. The age distribution of patients was not significantly different between the two groups. There was no statistically significant difference in the sex ratio, risk factors, and NIHSS score between the two groups (P > 0.05). The higher frequency of stroke onset time in the BR group was in the time between 6:00 a.m. and noon; whereas the frequency was higher between noon and 6:00 p.m. in the DR group. CONCLUSION A significant shift of the circadian pattern of stroke onset time from the period between 6:00 a.m. and noon to that between noon and 6:00 pm has been found during the month of Ramadan.
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Affiliation(s)
- A El-Mitwalli
- Department of Neurology, University of Mansoura, Mansoura, Egypt
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16
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Atkinson G, Jones H, Ainslie PN. Circadian variation in the circulatory responses to exercise: relevance to the morning peaks in strokes and cardiac events. Eur J Appl Physiol 2009; 108:15-29. [PMID: 19826832 DOI: 10.1007/s00421-009-1243-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2009] [Indexed: 10/20/2022]
Abstract
Sudden cardiac and cerebral events are most common in the morning. A fundamental question is whether these events are triggered by the increase in physical activity after waking, and/or a result of circadian variation in the responses of circulatory function to exercise. Although signaling pathways from the master circadian clock in the suprachiasmatic nuclei to sites of circulatory control are not yet understood, it is known that cerebral blood flow, autoregulation and cerebrovascular reactivity to changes in CO(2) are impaired in the morning and, therefore, could explain the increased risk of cerebrovascular events. Blood pressure (BP) and the rate pressure product (RPP) show marked 'morning surges' when people are studied in free-living conditions, making the rupture of a fragile atherosclerotic plaque and sudden cardiac event more likely. Since cerebral autoregulation is reduced in the morning, this surge in BP may also exacerbate the risk of hemorrhagic and ischemic strokes in the presence of other acute and chronic risk factors. Increased sympathetic activity, decreased endothelial function, and increased platelet aggregability could also be important in explaining the morning peak in cardiac and cerebral events but how these factors respond to exercise at different times of day is unclear. Evidence is emerging that the exercise-related responses of BP and RPP are increased in the morning when prior sleep is controlled. We recommend that such 'semi-constant routine' protocols are employed to examine the relative influence of the body clock and exogenous factors on the 24-h variation in other circulatory factors.
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Affiliation(s)
- Greg Atkinson
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK.
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17
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Manfredini R, Boari B, Smolensky MH, Salmi R, la Cecilia O, Maria Malagoni A, Haus E, Manfredini F. Circadian Variation in Stroke Onset: Identical Temporal Pattern in Ischemic and Hemorrhagic Events. Chronobiol Int 2009; 22:417-53. [PMID: 16076646 DOI: 10.1081/cbi-200062927] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Stroke is the culmination of a heterogeneous group of cerebrovascular diseases that is manifested as ischemia or hemorrhage of one or more blood vessels of the brain. The occurrence of many acute cardiovascular events--such as myocardial infarction, sudden cardiac death, pulmonary embolism, critical limb ischemia, and aortic aneurysm rupture--exhibits prominent 24 h patterning, with a major morning peak and secondary early evening peak. The incidence of stroke exhibits the same 24 h pattern. Although ischemic and hemorrhagic strokes are different entities and are characterized by different pathophysiological mechanisms, they share an identical double-peak 24 h pattern. A constellation of endogenous circadian rhythms and exogenous cyclic factors are involved. The staging of the circadian rhythms in vascular tone, coagulative balance, and blood pressure plus temporal patterns in posture, physical activity, emotional stress, and medication effects play central and/or triggering roles. Features of the circadian rhythm of blood pressure, in terms of their chronic and acute effects on cerebral vessels, and of coagulation are especially important. Clinical medicine has been most concerned with the prevention of stroke in the morning, when population-based studies show it is of greatest risk during the 24 h; however, improved protection of at-risk patients against stroke in the early evening, the second most vulnerable time of cerebrovascular accidents, has received relatively little attention thus far.
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Affiliation(s)
- Roberto Manfredini
- Vascular Diseases Center, Department of Clinical and Experimental Medicine, University of Ferrara, Italy.
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18
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Turin TC, Kita Y, Rumana N, Takashima N, Ichikawa M, Sugihara H, Morita Y, Hirose K, Murakami Y, Miura K, Okayama A, Nakamura Y, Abbott RD, Ueshima H. Morning surge in circadian periodicity of ischaemic stroke is independent of conventional risk factor status: findings from the Takashima Stroke Registry 1990-2003. Eur J Neurol 2009; 16:843-51. [DOI: 10.1111/j.1468-1331.2009.02605.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Urbano F, Roux F, Schindler J, Mohsenin V. Impaired cerebral autoregulation in obstructive sleep apnea. J Appl Physiol (1985) 2008; 105:1852-7. [DOI: 10.1152/japplphysiol.90900.2008] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Obstructive sleep apnea (OSA) increases the risk of stroke independent of known vascular and metabolic risk factors. Although patients with OSA have higher prevalence of hypertension and evidence of hypercoagulability, the mechanism of this increased risk is unknown. Obstructive apnea events are associated with surges in blood pressure, hypercapnia, and fluctuations in cerebral blood flow. These perturbations can adversely affect the cerebral circulation. We hypothesized that patients with OSA have impaired cerebral autoregulation, which may contribute to the increased risk of cerebral ischemia and stroke. We examined cerebral autoregulation in patients with and without OSA by measuring cerebral artery blood flow velocity (CBFV) by using transcranial Doppler ultrasound and arterial blood pressure using finger pulse photoplethysmography during orthostatic hypotension and recovery as well as during 5% CO2 inhalation. Cerebral vascular conductance and reactivity were determined. Forty-eight subjects, 26 controls (age 41.0±2.3 yr) and 22 OSA (age 46.8±2.3 yr) free of cerebrovascular and active coronary artery disease participated in this study. OSA patients had a mean apnea-hypopnea index of 78.4±7.1 vs. 1.8±0.3 events/h in controls. The oxygen saturation during sleep was significantly lower in the OSA group (78±2%) vs. 91±1% in controls. The dynamic vascular analysis showed mean CBFV was significantly lower in OSA patients compared with controls (48±3 vs. 55±2 cm/s; P <0.05, respectively). The OSA group had a lower rate of recovery of cerebrovascular conductance for a given drop in blood pressure compared with controls (0.06±0.02 vs. 0.20±0.06 cm·s−2·mmHg−1; P <0.05). There was no difference in cerebrovascular vasodilatation in response to CO2. The findings showed that patients with OSA have decreased CBFV at baseline and delayed cerebrovascular compensatory response to changes in blood pressure but not to CO2. These perturbations may increase the risk of cerebral ischemia during obstructive apnea.
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20
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Foerch C, Korf HW, Steinmetz H, Sitzer M. Abrupt shift of the pattern of diurnal variation in stroke onset with daylight saving time transitions. Circulation 2008; 118:284-90. [PMID: 18574046 DOI: 10.1161/circulationaha.108.771246] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Stroke onset shows a pattern of diurnal variation, with a peak in morning hours. Rhythmic changes in blood pressure, hormones, and other parameters have been suggested as underlying mechanisms, but exogenous factors such as increasing physical activity after awakening may also be of relevance. To characterize the impact of external clock changes on the rhythmic variation in stroke onset, this parameter was recorded in patients during transition periods into and out of Daylight Saving Time (DST). METHODS AND RESULTS The present study was based on a prospective stroke registry in Germany that contains time points of stroke onset from 44 251 patients admitted between 2000 and 2005. To achieve a uniform timeline, time points of stroke onset were set back from Central European Summer Time (CEST) to Central European Time (CET) for patients admitted during DST periods. Compared with the last week before the clock change, transition to or from DST resulted in an immediate shift of stroke onset time points within the first week after the clock change in reference to the uniform timeline (transition from CET to CEST -60 minutes for the time points in both the 25th and 50th percentiles of the diurnal pattern, P<0.001; transition from CEST to CET +60 minutes for the time points in both the 25th and 50th percentiles, P<0.001; patients pooled on a weekly basis). A significant shift was already present the first and second day after the transitions (ie, Monday and Tuesday). CONCLUSIONS Transition to or from DST is coupled with an immediate shift in the time pattern of stroke onset. This strengthens the idea that exogenous factors associated with awakening are important determinants of the pattern of diurnal variation of stroke onset, because entrainment of the human circadian clock within hours is unlikely.
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Affiliation(s)
- Christian Foerch
- Department of Neurology, Goethe University, Schleusenweg 2-16, 60528 Frankfurt am Main, Germany.
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21
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Haus E. Chronobiology of hemostasis and inferences for the chronotherapy of coagulation disorders and thrombosis prevention. Adv Drug Deliv Rev 2007; 59:966-84. [PMID: 17822804 DOI: 10.1016/j.addr.2006.11.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Accepted: 11/05/2006] [Indexed: 01/09/2023]
Abstract
The hemostatic system in its multiple components displays an intricate organization in time which is characterized by circadian (approximately 24-hour), circaseptan (approximately 7-day), menstrual (approximately monthly), and circannual (approximately yearly) bioperiodicities. The interaction of the rhythms of the variables participating in hemostasis determine transient risk states of thromboembolic events, including myocardial infarction and stroke, and of hemorrhage and hemorrhagic events, each with a unique timing. The circadian staging of the rhythms in vascular, cellular, and coagulation factors that favors blood coagulation and thrombosis coincides with the daily minimum in fibrinolytic activity; as a result there is elevated risk in the morning of acute myocardial infarction and stroke. Similar hemostatic rhythms may determine the epidemiology of thromboembolic and hemorrhagic events during the week, month and year. This article focuses on the large-amplitude circadian rhythms operative in the hemostatic system. Their implication for preventive and curative pharmacotherapy of hemostatic disorders is presented, with discussion of related problems.
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Affiliation(s)
- Erhard Haus
- University of Minnesota, HealthPartners Medical Group, Regions Hospital, St. Paul 55101, USA.
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22
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23
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Ainslie PN, Murrell C, Peebles K, Swart M, Skinner MA, Williams MJA, Taylor RD. Early morning impairment in cerebral autoregulation and cerebrovascular CO2reactivity in healthy humans: relation to endothelial function. Exp Physiol 2007; 92:769-77. [PMID: 17384117 DOI: 10.1113/expphysiol.2006.036814] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The reduction in cerebrovascular reactivity to CO(2) and/or endothelial function that occurs in the early hours after waking are potential causes for the increased risk for cardiovascular events at this time point. It is unknown whether cerebral autoregulation is reduced in the morning. We tested the hypothesis that early morning reduction in endothelium-dependent vascular reactivity would be linked to changes in cerebrovascular reactivity to CO(2) and cerebral autoregulation (CA). Overnight changes in a dynamic cerebral autoregulation index (ARI) were determined from continuous recordings of blood flow velocity in the middle cerebral artery (MCAv) and arterial blood pressure (BP) during transiently induced hypotension in 20 individuals. Frontal cortical oxygenation (near infrared spectroscopy) and cerebral haemodynamics were also monitored during hypercapnia and before and during 3 min of active standing. Brachial artery flow-mediated endothelium-dependent vasodilatation (FMD) and endothelium-independent dilatation (NFMD) were also monitored. From evening to morning, there was a significant lowering in ARI (5.3 +/- 0.5 versus 4.7 +/- 0.6 a.u.; P < 0.05), cerebrovascular reactivity to CO(2) (5.3 +/- 0.6 versus 4.6 +/- 1.1% mmHg(-1); P < 0.05) and FMD (7.6 +/- 0.9 versus 6.0 +/- 1.4%; P < 0.05). The lowered FMD was related to the decrease in cerebrovascular reactivity to CO(2) (r = 0.76; P < 0.05). Transient reductions in morning MCAv and cortical oxyhaemoglobin concentrations were observed upon resuming a supine-to-upright position (P < 0.05 versus evening). The early morning reduction in cerebral autoregulation may facilitate the onset of cerebrovascular accidents; this may be of particular relevance to at-risk groups, especially upon resuming the upright position.
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Affiliation(s)
- Philip N Ainslie
- Department of Physiology, University of Otago, Dunedin, New Zealand.
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24
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Ivancev V, Palada I, Valic Z, Obad A, Bakovic D, Dietz NM, Joyner MJ, Dujic Z. Cerebrovascular reactivity to hypercapnia is unimpaired in breath-hold divers. J Physiol 2007; 582:723-30. [PMID: 17412771 PMCID: PMC2075341 DOI: 10.1113/jphysiol.2007.128991] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Hypercapnic cerebrovascular reactivity is decreased in obstructive sleep apnoea and congestive heart disease perhaps as a result of repeated apnoeas. To test the hypothesis that repeated apnoeas blunt cerebrovascular reactivity to hypercapnia, we studied breath hold divers and determined cerebrovascular reactivity by measuring changes in middle cerebral artery velocity (MCAV, cm s(-1)) per mmHg change in end-tidal partial pressure of CO2(PET,CO2 ) in response to two hyperoxic hypercapnia rebreathing manoeuvres (modified Read protocol) in elite breath-hold divers (BHD, n=7) and non-divers (ND, n=7). In addition, ventilation and central (beat-to-beat stroke volume measurement with Modelflow technique) haemodynamics were determined. Ventilatory responses to hypercapnia were blunted in BHD versus ND largely due to lower breathing frequency. Cerebrovascular reactivity did not differ between groups (3.7 +/- 1.4 versus 3.4 +/- 1.3% mmHg(-1) in BHD and ND, respectively; P=0.90) and the same was found for cerebral vascular resistance and MCAV recovery to baseline after termination of the CO2 challenge. Cardiovascular parameters were not changed significantly during rebreathing in either group, except for a small increase in mean arterial pressure for both groups. Our findings indicate that the regulation of the cerebral circulation in response to hypercapnia is intact in elite breath-hold divers, potentially as a protective mechanism against the chronic intermittent cerebral hypoxia and/or hypercapnia that occurs during breath-hold diving. These data also suggest that factors other than repeated apnoeas contribute to the blunting of cerebrovascular reactivity in conditions like sleep apnoea.
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Affiliation(s)
- Vladimir Ivancev
- Department of Physiology, University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia
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25
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Ameriso SF, Lagos R, Ferreira LM, Fernández Cisneros L, La Mura AR. Cerebrovascular Effects of Cilostazol in Patients With Atherosclerotic Disease. J Stroke Cerebrovasc Dis 2006; 15:273-6. [PMID: 17904087 DOI: 10.1016/j.jstrokecerebrovasdis.2006.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 07/20/2006] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Cilostazol is a potent selective inhibitor of phosphodiesterase-3 of proven efficacy in intermittent claudication. It has antiplatelet effect and produces vasodilatation in several vascular territories. This drug has been approved in some countries for the prevention of recurrence of cerebral infarction. Limited data in patients with cerebral infarcts suggest improvement in cerebral blood flow. Dilatation of cerebral vessels with carbon-dioxide challenge can be assessed by transcranial Doppler technique. The percentage increase in blood flow velocity is called cerebral vasomotor reactivity (CVR). OBJECTIVE In this investigation we sought to measure CVR before and after oral administration of cilostazol. METHODS We studied patients with risk factors for atherosclerosis before they received cilostazol (100 mg twice daily) for intermittent claudication. CVR was assessed by measuring bilateral middle cerebral artery blood flow velocity during normoventilation and after 3 minutes of breathing 8% carbon dioxide. One average value was obtained from each patient. CVR was measured the day before cilostazol first dose, at 1 month, and 3 to 6 months later. RESULTS We examined 9 patients (8 men and 1 woman) aged 67.6 +/- 8.4 years. All patients had hypertension, 5 had diabetes, 4 were smokers, 5 had high cholesterol levels, and 4 had coronary artery disease. CVR was 54.4 +/- 14.4% at baseline, and increased to 64.2 +/- 18.6% after 1 month (P < .05) and to 67.1 +/- 13.3% at 3 to 6 months later (P < .01). CONCLUSION Our findings suggest that cilostazol increases CVR in patients with atherosclerotic disease.
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Affiliation(s)
- Sebastián F Ameriso
- Department of Neurology, Institute for Neurological Research, FLENI, Buenos Aires, Argentina
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26
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Nöth U, Meadows GE, Kotajima F, Deichmann R, Corfield DR, Turner R. Cerebral vascular response to hypercapnia: Determination with perfusion MRI at 1.5 and 3.0 Tesla using a pulsed arterial spin labeling technique. J Magn Reson Imaging 2006; 24:1229-35. [PMID: 17094105 DOI: 10.1002/jmri.20761] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To compare the quantification of cerebral blood flow (CBF) at 1.5 and 3.0 Tesla, under normo- and hypercapnia, and to determine the cerebral vascular response (CVR) of gray matter (GM) to hypercapnia, a pulsed arterial spin labeling technique was used. Additionally, to improve GM CBF quantification a high-resolution GM-mask was applied. MATERIALS AND METHODS CBF was determined with the QUIPSS II with thin slice TI1 periodic saturation (Q2TIPS) sequence at 1.5 and 3.0 Tesla in the same group of eight subjects, both under normocapnia and hypercapnia. Absolute GM-CBF maps were calculated using a GM-mask obtained from a high-resolution structural scan by segmentation. The CVR to hypercapnia was derived from the quantitative GM-CBF maps. RESULTS For both field strengths, the GM-CBF was significantly higher under hypercapnia compared to normocapnia. For both conditions, there was no significant difference of GM-CBF for 1.5 and 3.0 Tesla; the same applies to the CVR, which was 4.3 and 4.5%/mmHg at 1.5 and 3.0 Tesla, respectively. CONCLUSION The method presented allows for the quantification of CBF and CVR in GM at the common clinical field strengths of 1.5 and 3.0 Tesla and could therefore be a useful tool to study these parameters under physiological and pathophysiological conditions.
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Affiliation(s)
- Ulrike Nöth
- Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London, London, UK.
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27
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Schroeter ML, Bücheler MM, Scheid R. Circadian variability is negligible in primary visual cortices as measured by fNIRS. Int J Psychophysiol 2005; 62:9-13. [PMID: 16343672 DOI: 10.1016/j.ijpsycho.2005.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 10/21/2005] [Accepted: 11/09/2005] [Indexed: 11/28/2022]
Abstract
Neural activation leads to an increase of regional cerebral blood flow. Most of the functional imaging studies implicitly assume that variability of the hemodynamic response throughout a single day is negligible. To test this assumption we measured brain activation by functional near-infrared spectroscopy (fNIRS) in the visual cortex of ten subjects six times throughout the day, from 0800-1800 h, during an event-related checkerboard paradigm. Concentration of oxygenated hemoglobin increased, whereas concentration of deoxygenated hemoglobin decreased at each time point examined, without significant influences of daytime. Variability of the hemodynamic response was higher across subjects than for single subjects across day. In conclusion, our study is the first one supporting the common practice of ignoring circadian variability in functional imaging studies.
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Affiliation(s)
- Matthias L Schroeter
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1A, 04103 Leipzig, Germany.
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Abstract
A particular pattern of circadian variation of cardiovascular and cerebrovascular diseases has been reported in the literature. The circadian periodicity of ischaemic stroke with peak onset in the morning hours may not be a random event and could depend on some underlying precipitating and associated cardiovascular risk factors. In a prospective observational study, we observed that ischaemic stroke onset was significantly higher in late morning hours between 6.00 and 12.00 hours. Ischaemic heart disease and hypertension were significantly associated with the occurrence of late morning ischaemic strokes. Further studies in the future are needed to understand the significance of this association and whether these risk factors are implicated in the pathogenesis of stroke.
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Affiliation(s)
- A Gupta
- West Wales hospital, Carmarthen, UK.
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Meadows GE, Kotajima F, Vazir A, Kostikas K, Simonds AK, Morrell MJ, Corfield DR. Overnight Changes in the Cerebral Vascular Response to Isocapnic Hypoxia and Hypercapnia in Healthy Humans. Stroke 2005; 36:2367-72. [PMID: 16224083 DOI: 10.1161/01.str.0000185923.49484.0f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
The reduction in hypercapnic cerebral vascular reactivity that occurs in the morning after sleep is associated with an increased risk of cerebral ischemia and stroke. It is not known if the cerebral vascular response to hypoxia is similarly reduced in the morning, but such a reduction could be considered a further risk factor for cerebral vascular disease.
Methods—
To test if the cerebral vascular response to hypoxia is reduced in the morning, the overnight changes in the left middle cerebral artery velocity (MCAV) in response to isocapnic hypoxia (IH) and hypercapnia before and after a normal night sleep were determined in 18 individuals.
Results—
From evening to morning, hypercapnic cerebral vascular reactivity decreased significantly (evening 2.0±0.4, morning 1.3±0.2 cm/sec/mm Hg;
P
<0.05); in contrast, the increase in MCAV in response to IH (−10% SaO
2
) was unchanged (evening 9.0±1.4, morning 8.7±2.2%;
P
>0.05).
Conclusions—
Our findings indicate that substantial differences exist in the regulation of the cerebral circulation in response to hypoxia and hypercapnia on waking from sleep. An intact cerebral vascular response to IH, during this time period, could be interpreted as a protective mechanism against cerebral ischemia and stroke; this is of particular relevance to patients with obstructive sleep apnea who arouse from sleep during hypoxia.
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Affiliation(s)
- Guy E Meadows
- Clinical and Academic Unit of Sleep and Breathing, National Heart and Lung Institute, Imperial College, London, UK
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30
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Kotajima F, Meadows GE, Morrell MJ, Corfield DR. Cerebral blood flow changes associated with fluctuations in alpha and theta rhythm during sleep onset in humans. J Physiol 2005; 568:305-13. [PMID: 16002438 PMCID: PMC1474761 DOI: 10.1113/jphysiol.2005.092577] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/14/2005] [Accepted: 07/05/2005] [Indexed: 12/30/2022] Open
Abstract
Cerebral blood flow (CBF) is typically reduced during stable non-rapid eye movement (non-REM) sleep compared with the waking level. It is not known when in the sleep cycle these changes occur. However, spontaneous fluctuations in alpha and theta rhythm during sleep onset are associated with marked changes in cardio-respiratory control. The aim of this study was to test the hypothesis that changes in CBF would occur during sleep onset and would be related to changes in cortical activity. Middle cerebral artery velocity (MCAV) was measured using transcranial Doppler ultrasound, as an index of CBF, in 10 healthy subjects. Sleep state, ventilation, end tidal carbon dioxide (PET,CO2), arterial oxygen saturation (SaO2), mean arterial blood pressure (MABP) and cardiac R-R interval (RR) were monitored simultaneously. Immediately following the transition from alpha to theta rhythm (the transition from wake to sleep), ventilation decreased by 13.4% and tidal volume (VT) by 12.2% (P<0.01); PET,CO2 increased by 1.9% (P<0.01); respiratory frequency (fR) and SaO2 did not change significantly. MCAV increased by 9.7% (P<0.01); MABP decreased by 3.2% (P<0.01) but RR did not change significantly. Immediately following the transition from theta to alpha rhythm (spontaneous awakening), increased by 13.3% (P<0.01); VT increased by 11.4% (P<0.01); PET,CO2 decreased by 1.9% (P<0.01); MCAV decreased by 11.1% (P<0.01) and MABP decreased by 7.5%; fR, SaO2 and RR did not change significantly. These changes in MCAV during sleep onset cannot be attributed to changes in ventilation or MABP. We speculate that the changes in cerebral vascular tone during sleep onset are mediated neurally, by regulatory mechanisms linked to the changes in cortical state, and that these mechanisms are different from those regulating the longer-term reduction in CBF associated with stable non-REM sleep.
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Xie A, Skatrud JB, Khayat R, Dempsey JA, Morgan B, Russell D. Cerebrovascular Response to Carbon Dioxide in Patients with Congestive Heart Failure. Am J Respir Crit Care Med 2005; 172:371-8. [PMID: 15901613 DOI: 10.1164/rccm.200406-807oc] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Cerebrovascular reactivity to CO(2) provides an important counterregulatory mechanism that serves to minimize the change in H(+) at the central chemoreceptor, thereby stabilizing the breathing pattern in the face of perturbations in Pa(CO(2)). However, there are no studies relating cerebral circulation abnormality to the presence or absence of central sleep apnea in patients with heart failure. OBJECTIVES To determine whether patients with congestive heart failure and central sleep apnea have an attenuated cerebrovascular responsibility to CO(2). METHODS Cerebral blood flow velocity in the middle cerebral artery was measured in patients with stable congestive heart failure with (n = 9) and without (n = 8) central sleep apnea using transcranial ultrasound during eucapnia (room air), hypercapnia (inspired CO(2), 3 and 5%), and hypocapnia (voluntary hyperventilation). In addition, eight subjects with apnea and nine without apnea performed a 20-second breath-hold to investigate the dynamic cerebrovascular response to apnea. MEASUREMENTS AND MAIN RESULTS The overall cerebrovascular reactivity to CO(2) (hyper- and hypocapnia) was lower in patients with apnea than in the control group (1.8 +/- 0.2 vs. 2.5 +/- 0.2%/mm Hg, p < 0.05), mainly due to the prominent reduction of cerebrovascular reactivity to hypocapnia (1.2 +/- 0.3 vs. 2.2 +/- 0.1%/mm Hg, p < 0.05). Similarly, brain blood flow demonstrated a smaller surge after a 20-second breath-hold (peak velocity, 119 +/- 4 vs. 141 +/- 8% of baseline, p < 0.05). CONCLUSION Patients with central sleep apnea have a diminished cerebrovascular response to PET(CO(2)), especially to hypocapnia. The compromised cerebrovascular reactivity to CO(2) might affect stability of the breathing pattern by causing ventilatory overshooting during hypercapnia and undershooting during hypocapnia.
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Affiliation(s)
- Ailiang Xie
- Department of Medicine, University of Wisconsin, Madison, 53705, USA.
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Conroy DA, Spielman AJ, Scott RQ. Daily rhythm of cerebral blood flow velocity. J Circadian Rhythms 2005; 3:3. [PMID: 15760472 PMCID: PMC555580 DOI: 10.1186/1740-3391-3-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Accepted: 03/10/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND: CBFV (cerebral blood flow velocity) is lower in the morning than in the afternoon and evening. Two hypotheses have been proposed to explain the time of day changes in CBFV: 1) CBFV changes are due to sleep-associated processes or 2) time of day changes in CBFV are due to an endogenous circadian rhythm independent of sleep. The aim of this study was to examine CBFV over 30 hours of sustained wakefulness to determine whether CBFV exhibits fluctuations associated with time of day. METHODS: Eleven subjects underwent a modified constant routine protocol. CBFV from the middle cerebral artery was monitored by chronic recording of Transcranial Doppler (TCD) ultrasonography. Other variables included core body temperature (CBT), end-tidal carbon dioxide (EtCO2), blood pressure, and heart rate. Salivary dim light melatonin onset (DLMO) served as a measure of endogenous circadian phase position. RESULTS: A non-linear multiple regression, cosine fit analysis revealed that both the CBT and CBFV rhythm fit a 24 hour rhythm (R2 = 0.62 and R2 = 0.68, respectively). Circadian phase position of CBT occurred at 6:05 am while CBFV occurred at 12:02 pm, revealing a six hour, or 90 degree difference between these two rhythms (t = 4.9, df = 10, p < 0.01). Once aligned, the rhythm of CBFV closely tracked the rhythm of CBT as demonstrated by the substantial correlation between these two measures (r = 0.77, p < 0.01). CONCLUSION: In conclusion, time of day variations in CBFV have an approximately 24 hour rhythm under constant conditions, suggesting regulation by a circadian oscillator. The 90 degree-phase angle difference between the CBT and CBFV rhythms may help explain previous findings of lower CBFV values in the morning. The phase difference occurs at a time period during which cognitive performance decrements have been observed and when both cardiovascular and cerebrovascular events occur more frequently. The mechanisms underlying this phase angle difference require further exploration.
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Affiliation(s)
- Deirdre A Conroy
- Department of Psychology, The Graduate School and University Center of the City University of New York, New York, USA
| | - Arthur J Spielman
- Department of Psychology, The Graduate School and University Center of the City University of New York, New York, USA
- Department of Neurology and Neuroscience, New York Presbyterian Hospital, New York, USA
| | - Rebecca Q Scott
- Department of Health Psychology, Albert Einstein Medical College at Yeshiva University, Bronx, USA
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Park CW, Sturzenegger M, Douville CM, Aaslid R, Newell DW. Autoregulatory response and CO2 reactivity of the basilar artery. Stroke 2003; 34:34-9. [PMID: 12511747 DOI: 10.1161/01.str.0000047122.42591.b3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Transcranial Doppler has been extensively used to measure cerebrovascular control mechanisms, including autoregulation in humans and in patients with cerebrovascular diseases. There have been sufficient reports on the measurement of normal autoregulatory response (AR) and CO2 reactivity (CR) of the middle cerebral artery (MCA) but few reports of these indices for the basilar artery (BA). We measured AR and CR in the BA in healthy volunteers to determine normal values and compared them with simultaneous measurements made in the MCA. METHODS Sixteen normal subjects were enrolled. Time-averaged mean velocities of maximum blood flow in the BA and MCA were continuously and simultaneously monitored by using transcranial Doppler along with continuous measurement of mean arterial blood pressure (MABP). Values were obtained during rest, alterations of end-tidal PaCO2 (ETCO2), and acute decrease and recovery of MABP. AR was evaluated by using the thigh cuff method and graded by the standard dynamic autoregulatory index (ARI), with values between 0 and 9. CR was measured as percentage change in time-averaged mean velocity per mm Hg ETCO2. RESULTS The mean age of 16 subjects was 27.38+/-8.50 years. Average baseline values for MABP and ETCO2 were 82.29+/-7.10 and 42.75+/-3.77 mm Hg, respectively. Mean ARI was 4.62+/-1.26 for the BA and was 4.77+/-1.23 for the MCA (n=15) (P=0.598). Average CR was 2.54+/-0.39%/mm Hg ETCO2 for the BA and 2.51+/-0.29%/mm Hg ETCO2 for the MCA (n=16) (P=0.686). CONCLUSIONS Our study demonstrates that ARI and CR values for the BA are similar to those for the MCA.
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Affiliation(s)
- Cheol Wan Park
- Cerebrovascular Laboratory, Department of Neurological Surgery, University of Washington School of Medicine, Harborview Medical Center, Seattle 98104-2499, USA.
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Abstract
Obstructive sleep apnoeas are common among stroke patients and, as different from central apnoeas, they do not decline during stroke rehabilitation. Cerebral and cardiovascular changes display a different pattern during central and obstructive sleep apnoeas. The cerebral blood flow velocity according to transcranial Doppler increases during an obstructive apnoea and decreases after apnoea termination concomitant with changes in arterial pressure. The changes in cerebral circulation during obstructive apnoeas could be an immediate effect of rapid changes in blood pressure because cerebral autoregulation is overridden. Low cerebral blood flow, low arterial pressure and hypoxemia after apnoea termination may predispose to nocturnal cerebral ischaemia. The opposite pattern is seen during a central apnoea, with a decrease in cerebral blood flow velocity during apnoea and an increase after apnoea termination. Changes during obstructive apnoeas are probably hazardous, with adverse cardiovascular effects including stroke. This may not be the case during central apnoeas, as Cheyne-Stokes respiration with central apnoeas is a result of an underlying disorder such as heart failure and stroke and is not a disease entity in itself. It is suggested that obstructive sleep apnoea is a risk factor for stroke as it is common among stroke victims and cerebral hypoperfusion occurs after an obstructive apnoea. The treatment of sleep apnoea should also be taken into account among stroke patients. Large cohort studies, treatment studies and further studies of possible mechanisms for apnoea-induced stroke are, however, essential in order to evaluate whether obstructive sleep apnoea is an independent risk factor for stroke.
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Affiliation(s)
- Karl A Franklin
- Department of Respiratory Medicine, University Hospital, SE-901 85 Umeå, Sweden.
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Gur AY, Bornstein NM. Are there any unique epidemiological and vascular risk factors for ischaemic strokes that occur in the morning hours? Eur J Neurol 2000; 7:179-81. [PMID: 10809938 DOI: 10.1046/j.1468-1331.2000.00010.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It is now accepted that the incidence of ischaemic stroke is significantly increased in the morning. Any attempts to prevent its occurrence must be based on determining the mechanisms, special risk factors and appropriate protective measures needed during this vulnerable period. We studied the epidemiological features of morning stroke and reviewed the records of 2312 consecutive patients recorded prospectively in the Tel Aviv Stroke Register. Information about time of stroke onset was obtained from the patient, family members or other observers. The study parameters of age, sex, vascular distribution (carotid versus vertebrobasilar), ischaemic heart disease, myocardial infarction, diabetes mellitus, arterial hypertension, smoking, hyperlipidaemia, stroke severity and recurrence were compared between patients with morning stroke and those with stroke occurring at other times. In 599 patients (34%) stroke occurred between 06:00 and 10:00 h. No evaluated parameter was found to be statistically different among the morning stroke patients compared with stroke occurring at other times (P < 0.2). Patients with arterial hypertension and ischaemic heart disease and male patients had a greater likelihood of stroke occurrence between 22:00 and 02:00 h (P < 0.05). Our data suggest that none of the common vascular risk factors could explain the morning peak of stroke occurrence. The next step in the quest for understanding the phenomenon of circadian variation is to identify other physiological factors and the effects of pharmacological agents in morning stroke protection.
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Affiliation(s)
- A Y Gur
- Stroke Unit, Department of Neurology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
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Qureshi AI, Christopher Winter W, Bliwise DL. Sleep fragmentation and morning cerebrovasomotor reactivity to hypercapnia. Am J Respir Crit Care Med 1999; 160:1244-7. [PMID: 10508814 DOI: 10.1164/ajrccm.160.4.9810111] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Impaired vasomotor reactivity of the cerebral vessels on morning awakening has been suggested as one of the mechanisms underlying the predisposition to stroke in the morning. This study investigated cerebrovascular reactivity to hypercapnia on morning awakening and its association with specific sleep-related parameters, including sleep-disordered breathing. Thirty patients undergoing nocturnal diagnostic polysomnography for sleep apnea underwent transcranial Doppler ultrasonography of the middle cerebral artery immediately before going to bed and immediately on morning awakening. Results indicated a morning reduction in cerebral blood flow velocity (CBFV) relative to values from the preceding evening both while breathing room air and 5% CO(2). Hypercapnia was associated with the expected increase in CBFV in both evening and morning. The evening-to-morning difference in CBFV during CO(2) inhalation was independently associated with both overnight CO(2) retention and number of movements with arousal per hour of sleep. Results indicated that more fragmented sleep and greater CO(2) retention during sleep predicted a diminished hypercapnic vasomotor response in the morning. Sleep fragmentation predicted approximately twice the variance in morning hypercapnic vasomotor reactivity relative to overnight CO(2) retention (24 versus 13%). No other polysomnographic measures predicted evening-to-morning differences in vasomotor reactivity. These results are consistent with a body of literature suggesting that sleep loss and sleep fragmentation are associated with blunted hypercapnic ventilatory response.
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Affiliation(s)
- A I Qureshi
- Sleep Disorders Center, Department of Neurology, Emory University Medical School, Atlanta, Georgia, USA
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Portaluppi F, Manfredini R, Fersini C. From a static to a dynamic concept of risk: the circadian epidemiology of cardiovascular events. Chronobiol Int 1999; 16:33-49. [PMID: 10023574 DOI: 10.3109/07420529908998710] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A growing body of evidence substantiates that the occurrence of cardiovascular events in unevenly distributed in time, especially during the 24 h. These temporal patterns are indicative of temporal variation in the (1) pathophysiological mechanisms that trigger cardiovascular events and (2) physiological status of the cardiovascular system, which combine to give rise to 24 h and other periodicities in the susceptibility to disease. The classic assumption of epidemiologic studies is constancy (or homeostasis) in one's risk to disease during the 24 h, as well as other, time domains. However, we propose a new concept, that of chronorisk since it takes into account the temporal variability in the pathophysiological mechanisms and their reciprocal temporal interactions that lead to day-night and other time-dependent patterns in cardiovascular events. This chronobiological approach, which is expected to contribute new insight into the prognostic and therapeutic assessment of cardiovascular events, is worthy of broader application in cardiovascular and other fields of medicine and warrants further investigation.
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Affiliation(s)
- F Portaluppi
- Hypertension Unit, University of Ferrara, Italy.
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38
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Knecht S, Deppe M, Ringelstein EB, Wirtz M, Lohmann H, Dräger B, Huber T, Henningsen H. Reproducibility of functional transcranial Doppler sonography in determining hemispheric language lateralization. Stroke 1998; 29:1155-9. [PMID: 9626288 DOI: 10.1161/01.str.29.6.1155] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Since functional transcranial Doppler ultrasonography (fTCD) allows convenient and fully automated quantification of language lateralization, it seems ideal for longitudinal studies of perfusion changes during deterioration as well as recovery of language functions. However, during serial examinations, the technical, stochastic, and physiological variabilities of cerebral blood flow velocities (CBFV) have to be considered. Therefore, before fTCD is accepted as a tool for evaluation of changes in lateralization in the diseased state, its reliability in healthy subjects needs to be determined. METHODS We performed fTCD during a word generation task based on a previously validated technique with automated calculation of the averaged CBFV differences in the middle cerebral arteries providing an index of lateralization (LI). RESULTS (1) The accuracy of the LI as assessed by the confidence interval was better than 1% of the mean hemispheric difference. (2) On repeated examination, LIs obtained from 10 subjects showed a high test-retest reproducibility (Pearson product moment correlation coefficient r = 0.95, P < 0.0001). (3) On 10 repeated assessments of LI in the same subject, no practice effects were detected. CONCLUSIONS Functional TCD is a suitable and very robust tool for the longitudinal quantitative measurement of cerebral language lateralization.
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Affiliation(s)
- S Knecht
- Department of Neurology, University of Münster, Germany.
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Manfredini R, Gallerani M, Portaluppi F, Salmi R, Fersini C. Chronobiological patterns of onset of acute cerebrovascular diseases. Thromb Res 1997; 88:451-63. [PMID: 9610956 DOI: 10.1016/s0049-3848(97)00286-7] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
There is a considerable amount of data indicating that several major unfavorable cerebrovascular events are not randomly distributed over time, but show a peculiar distribution along the day, the week, and the months of the year. The authors review the available evidence on the chronobiological (circadian, weekly, and seasonal) patterns of onset of acute cerebrovascular diseases and variations in their possible triggering mechanisms. The existence of a peculiar chronobiological pattern in the onset of acute cerebrovascular disease, characterized by both circadian (morning and evening occurrence), circaseptan (last and first days of the week), and circannual (especially in winter) is confirmed, although differences depending on biological (gender, age), pathological (diabetes, hypertension, smoke, alcohol), cultural, social, and environmental factors exist. A deeper knowledge of the underlying pathophysiologic mechanisms could provide more effective insights for both preventive strategies and optimization of therapeutic approach.
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Affiliation(s)
- R Manfredini
- First Institute of Internal Medicine, Department of Clinical and Experimental Medicine, University of Ferrara, Italy
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40
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Cencetti S, Bandinelli G, Lagi A. Effect of PCO2 changes induced by head-upright tilt on transcranial Doppler recordings. Stroke 1997; 28:1195-7. [PMID: 9183350 DOI: 10.1161/01.str.28.6.1195] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND PURPOSE Transcranial Doppler (TCD) monitoring of mean blood flow velocity (mV) during head-upright tilt can allow testing of cerebral autoregulation. Nonetheless, head-upright tilt can induce changes in the ventilation-perfusion relationship and/or respiratory activity that might influence TCD data. METHODS Forty-eight healthy volunteers underwent monitoring of mV and end-tidal CO2 in the horizontal position and during head-upright tilt. RESULTS Both mV and end-tidal CO2 significantly decreased in orthostasis (P < .01). Linear regression analysis showed a significant linkage between end-tidal CO2 and mV changes (r = .83, P < .01). CONCLUSIONS Changes in ventilation-perfusion ratio and in the respiratory pattern induced by head-upright tilt can significantly influence TCD data by determining a PCO2 decrease.
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Affiliation(s)
- S Cencetti
- Department of Internal Medicine 1. S Maria Nuova Hospital, Florence, Italy
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41
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Affiliation(s)
- W J Schwartz
- Department of Neurology, University of Massachusetts Medical School, Worcester 01655, USA
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42
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Manfredini R, Gallerani M, Portaluppi F, Fersini C. Relationships of the circadian rhythms of thrombotic, ischemic, hemorrhagic, and arrhythmic events to blood pressure rhythms. Ann N Y Acad Sci 1996; 783:141-58. [PMID: 8853639 DOI: 10.1111/j.1749-6632.1996.tb26713.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Convincing evidence has recently accumulated that several unfavorable cardiovascular events show a well defined pattern in their occurrence throughout the day. Myocardial angina and infarction, sudden cardiac death, arrhythmias, fatal pulmonary thromboembolism, and ischemic and hemorrhagic cerebrovascular accidents occur more frequently in the morning, after awaking, until noon. Diurnal variations in multiple biologic functions, such as assumption of an upright posture associated with increased platelet aggregability, changes in blood clotting, fibrinolysis, and vascular tone and resistance, may be potentially active triggering factors. Moreover, variations in sympathetic tone, catecholamine secretion, and blood pressure have to be considered. The role of triggering factors and their relationships with blood pressure patterns is discussed in view of an optimized pharmacologic treatment.
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Affiliation(s)
- R Manfredini
- First Institute of Internal Medicine, Ferrara, Italy
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