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Title: Asymptomatic Carotid Stenosis Is Associated With Circadian and Other Variability in Embolus Detection.
Austin Authors: Abbott, Anne L;Merican, Julia;Pearce, Dora C;Juric, Ana;Worsnop, Christopher J ;Foster, Emma;Chambers, Brian R 
Affiliation: Respiratory and Sleep Medicine
School of Science, Engineering and Information Technology, Federation University, Ballarart, Victoria, Australia
Independent Researcher, Melbourne, Victoria, Australia
Central Clinical School, Monash University, Melbourne, Victoria, Australia
Neurology Department, Alfred Health, Melbourne, Victoria, Australia
Neurology Department, The Royal Melbourne Hospital, Melbourne, Victoria, Australia
Faculty of Medicine, University of Melbourne, Melbourne, Victoria, Australia
Neurology Network, Knox Private Hospital, Wantirna, Victoria, Australia
Neurology and Neurosurgery Centre, Princecourt Medical Centre, Kuala Lumpur, Malaysia
Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Victoria, Australia
Issue Date: 2019
Date: 2019
Publication information: Frontiers in Neurology 2019;10:322
Abstract: Background and Purpose: Variability in transcranial Doppler (TCD) detection of embolic signals (ES) is important for risk stratification. We tested the effect of time of day on ES associated with 60-99% asymptomatic carotid stenosis. Materials and Methods: Subjects were from the Asymptomatic Carotid Stenosis Embolus Detection (ASED) Study such that half were previously ES-positive and half ES-negative with 6-monthly 60-min TCD monitoring. All underwent bilateral TCD monitoring for two 12-h sessions separated by 24 h. ES detection rates were calculated using 6 and 4-h intervals from midnight and effective TCD monitoring time. Results: Ten subjects (8 male, mean age 79.5 years) were monitored. Over 24 h, 5/10 study arteries with 60-99% asymptomatic carotid stenosis were ES-positive (range 1-28 ES/artery, 56 total ES from 177.9 total effective monitoring hours). The remaining five study arteries and all eight successfully monitored contralateral arteries were ES-negative. Using 6-h intervals the mean ES detection rate peaked at 0600-midday (0.64/h) and was lowest 1800-midnight (0.09/h) with an incidence rate ratio of 7.26 (95% CI 2.52-28.64, P ≤ 0.001). Using 4-h intervals the mean ES detection rate peaked at 0800-midday (0.64/h) and was lowest midnight-0400 (0.12/h) with an incidence rate ratio of 5.51 (95% CI 1.78-22.67, P = 0.001). Conclusions: Embolism associated with asymptomatic carotid stenosis shows circadian variation with highest rates 4-6 h before midday. This corresponds with peak circadian incidence of stroke and other vascular complications. These and ASED Study results show that monitoring frequency, duration, and time of day are important in ES detection.
DOI: 10.3389/fneur.2019.00322
Journal: Frontiers in Neurology
PubMed URL: 31040812
ISSN: 1664-2295
Type: Journal Article
Subjects: carotid stenosis
sleep apnea
transcranial Doppler
Appears in Collections:Journal articles

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