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Bernjak A, Iqbal A, Heller SR, Clayton RH. Hypoglycaemia combined with mild hypokalaemia reduces the heart rate and causes abnormal pacemaker activity in a computational model of a human sinoatrial cell. J R Soc Interface 2021; 18:20210612. [PMID: 34814734 PMCID: PMC8611338 DOI: 10.1098/rsif.2021.0612] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Low blood glucose, hypoglycaemia, has been implicated as a possible contributing factor to sudden cardiac death (SCD) in people with diabetes but it is challenging to investigate in clinical studies. We hypothesized the effects of hypoglycaemia on the sinoatrial node (SAN) in the heart to be a candidate mechanism and adapted a computational model of the human SAN action potential developed by Fabbri et al., to investigate the effects of hypoglycaemia on the pacemaker rate. Using Latin hypercube sampling, we combined the effects of low glucose (LG) on the human ether-a-go-go-related gene channel with reduced blood potassium, hypokalaemia, and added sympathetic and parasympathetic stimulus. We showed that hypoglycaemia on its own causes a small decrease in heart rate but there was also a marked decrease in heart rate when combined with hypokalaemia. The effect of the sympathetic stimulus was diminished, causing a smaller increase in heart rate, with LG and hypokalaemia compared to normoglycaemia. By contrast, the effect of the parasympathetic stimulus was enhanced, causing a greater decrease in heart rate. We therefore demonstrate a potential mechanistic explanation for hypoglycaemia-induced bradycardia and show that sinus arrest is a plausible mechanism for SCD in people with diabetes.
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Affiliation(s)
- Alan Bernjak
- Department of Oncology and Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield S10 2RX, UK.,INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK
| | - Ahmed Iqbal
- Department of Oncology and Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield S10 2RX, UK.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Simon R Heller
- Department of Oncology and Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield S10 2RX, UK.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Richard H Clayton
- INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK.,Department of Computer Science, University of Sheffield, Sheffield, UK
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Ali Abdelhamid Y, Bernjak A, Phillips LK, Summers MJ, Weinel LM, Lange K, Chow E, Kar P, Horowitz M, Heller S, Deane AM. Nocturnal Hypoglycemia in Patients With Diabetes Discharged From ICUs: A Prospective Two-Center Cohort Study. Crit Care Med 2021; 49:636-649. [PMID: 33591015 DOI: 10.1097/ccm.0000000000004810] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVES There is very limited information about glycemic control after discharge from the ICU. The aims of this study were to evaluate the prevalence of hypoglycemia in ICU survivors with type-2 diabetes and determine whether hypoglycemia is associated with cardiac arrhythmias. DESIGN Prospective, observational, two-center study. Participants underwent up to 5 days of simultaneous blinded continuous interstitial glucose monitoring and ambulatory 12-lead electrocardiogram monitoring immediately after ICU discharge during ward-based care. Frequency of arrhythmias, heart rate variability, and cardiac repolarization markers were compared between hypoglycemia (interstitial glucose ≤ 3.5 mmol/L) and euglycemia (5-10 mmol/L) matched for time of day. SETTING Mixed medical-surgical ICUs in two geographically distinct university-affiliated hospitals. PATIENTS Patients with type-2 diabetes who were discharged from ICU after greater than or equal to 24 hours with greater than or equal to one organ failure and were prescribed subcutaneous insulin were eligible. MEASUREMENTS AND MAIN RESULTS Thirty-one participants (mean ± sd, age 65 ± 13 yr, glycated hemoglobin 64 ± 22 mmol/mol) were monitored for 101 ± 32 hours post-ICU (total 3,117 hr). Hypoglycemia occurred in 12 participants (39%; 95% CI, 22-56%) and was predominantly nocturnal (40/51 hr) and asymptomatic (25/29 episodes). Participants experiencing hypoglycemia had 2.4 ± 0.7 discrete episodes lasting 45 minutes (interquartile range, 25-140 min). Glucose nadir was less than or equal to 2.2 mmol/L in 34% of episodes. The longest episode of nocturnal hypoglycemia was 585 minutes with glucose nadir less than 2.2 mmol/L. Simultaneous electrocardiogram and continuous interstitial glucose monitoring recordings were obtained during 44 hours of hypoglycemia and 991 hours of euglycemia. Hypoglycemia was associated with greater risk of bradycardia but did not affect atrial or ventricular ectopics, heart rate variability, or cardiac repolarization. CONCLUSIONS In ICU survivors with insulin-treated type-2 diabetes, hypoglycemia occurs frequently and is predominantly nocturnal, asymptomatic, and prolonged.
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Affiliation(s)
- Yasmine Ali Abdelhamid
- Discipline of Acute Care Medicine, Department of Surgical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- Intensive Care Unit, Division of Critical Care and Investigative Services, Royal Melbourne Hospital, Parkville, VIC, Australia
- The University of Melbourne, Melbourne Medical School, Department of Medicine and Radiology, Royal Melbourne Hospital, Parkville, VIC, Australia
| | - Alan Bernjak
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom
- INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Liza K Phillips
- Discipline of Medicine, Department of Medical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- National Health and Medical Research Council Centre of Research Excellence in Translating Nutritional Science to Good Health, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Endocrine and Metabolic Service, Medical Services, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Matthew J Summers
- Discipline of Acute Care Medicine, Department of Surgical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- Intensive Care Unit, Critical Care Services, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Luke M Weinel
- Intensive Care Unit, Critical Care Services, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Kylie Lange
- Discipline of Medicine, Department of Medical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- National Health and Medical Research Council Centre of Research Excellence in Translating Nutritional Science to Good Health, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Elaine Chow
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Shatin, Hong Kong
| | - Palash Kar
- Discipline of Acute Care Medicine, Department of Surgical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- Intensive Care Unit, Critical Care Services, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Michael Horowitz
- Discipline of Medicine, Department of Medical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- National Health and Medical Research Council Centre of Research Excellence in Translating Nutritional Science to Good Health, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Endocrine and Metabolic Service, Medical Services, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Simon Heller
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom
- Sheffield Teaching Hospitals Foundation Trust, Sheffield, United Kingdom
| | - Adam M Deane
- Discipline of Acute Care Medicine, Department of Surgical Specialties, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- Intensive Care Unit, Division of Critical Care and Investigative Services, Royal Melbourne Hospital, Parkville, VIC, Australia
- The University of Melbourne, Melbourne Medical School, Department of Medicine and Radiology, Royal Melbourne Hospital, Parkville, VIC, Australia
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Bernjak A, Novodvorsky P, Chow E, Iqbal A, Sellors L, Williams S, Fawdry RA, Marques JLB, Jacques RM, Campbell MJ, Sheridan PJ, Heller SR. Cardiac arrhythmias and electrophysiologic responses during spontaneous hyperglycaemia in adults with type 1 diabetes mellitus. Diabetes Metab 2021; 47:101237. [PMID: 33647473 DOI: 10.1016/j.diabet.2021.101237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 12/21/2020] [Accepted: 02/08/2021] [Indexed: 01/19/2023]
Abstract
AIM We examined the effect of spontaneous hyperglycaemia in adults with type 1 diabetes mellitus (T1DM) and without history of cardiovascular disease on heart rate variability (HRV), cardiac repolarisation and incidence of cardiac arrhythmias. METHODS Thirty-seven individuals with T1DM (age 17-50 years, 19 males, mean duration of diabetes 19.3 SD(9.6) years) underwent 96 h of simultaneous ambulatory 12-lead Holter ECG and blinded continuous interstitial glucose (IG) monitoring (CGM). HRV, QT interval and cardiac repolarisation were assessed during hyperglycaemia (IG ≥ 15 mmol/l) and compared with matched euglycaemia (IG 5-10 mmol/l) on a different day, separately during the day and night. Rates of arrhythmias were assessed by calculating incidence rate differences. RESULTS Simultaneous ECG and CGM data were recorded for 2395 hours. During daytime hyperglycaemia vs euglycaemia the mean QTc interval duration was 404 SD(21)ms vs 407 SD(20)ms, P = 0.263. T-peak to T-end interval duration corrected for heart rate (TpTendc) shortened: 74.8 SD(16.1)ms vs 79.0 SD(14.8)ms, P = 0.033 and T-wave symmetry increased: 1.62 SD(0.33) vs 1.50 SD(0.39), P = 0.02. During night-time hyperglycaemia vs euglycaemia, the mean QTc interval duration was 401 SD(26)ms vs 404 SD(27)ms, P = 0.13 and TpTend shortened: 62.4 SD(12.0)ms vs 67.1 SD(11.8)ms, P = 0.003. The number of cardiac arrhythmias was low and confined to bradycardia and isolated ectopic beats. A considerable inter-subject and diurnal variability was observed. CONCLUSIONS Hyperglycaemia in individuals with T1DM without known cardiovascular disease was not associated with clinically important cardiac arrhythmias.
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Affiliation(s)
- A Bernjak
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, United Kingdom
| | - P Novodvorsky
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - E Chow
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom; Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - A Iqbal
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom; Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - L Sellors
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - S Williams
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - R A Fawdry
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - J L B Marques
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom
| | - R M Jacques
- School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom
| | - M J Campbell
- School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom
| | - P J Sheridan
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom; Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - S R Heller
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom.
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Bernjak A, Chow E, Robinson EJ, Freeman J, Marques JLB, Macdonald IA, Sheridan PJ, Heller SR. Influence of cardiac autonomic neuropathy on cardiac repolarisation during incremental adrenaline infusion in type 1 diabetes. Diabetologia 2020; 63:1066-1071. [PMID: 32030469 PMCID: PMC7145773 DOI: 10.1007/s00125-020-05106-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 01/13/2020] [Indexed: 11/01/2022]
Abstract
AIMS/HYPOTHESIS We examined the effect of a standardised sympathetic stimulus, incremental adrenaline (epinephrine) infusion on cardiac repolarisation in individuals with type 1 diabetes with normal autonomic function, subclinical autonomic neuropathy and established autonomic neuropathy. METHODS Ten individuals with normal autonomic function and baroreceptor sensitivity tests (NAF), seven with subclinical autonomic neuropathy (SAN; normal standard autonomic function tests and abnormal baroreceptor sensitivity tests); and five with established cardiac autonomic neuropathy (CAN; abnormal standard autonomic function and baroreceptor tests) underwent an incremental adrenaline infusion. Saline (0.9% NaCl) was infused for the first hour followed by 0.01 μg kg-1 min-1 and 0.03 μg kg-1 min-1 adrenaline for the second and third hours, respectively, and 0.06 μg kg-1 min-1 for the final 30 min. High resolution ECG monitoring for QTc duration, ventricular repolarisation parameters (T wave amplitude, T wave area symmetry ratio) and blood sampling for potassium and catecholamines was performed every 30 min. RESULTS Baseline heart rate was 68 (95% CI 60, 76) bpm for the NAF group, 73 (59, 87) bpm for the SAN group and 84 (78, 91) bpm for the CAN group. During adrenaline infusion the heart rate increased differently across the groups (p = 0.01). The maximum increase from baseline (95% CI) in the CAN group was 22 (13, 32) bpm compared with 11 (7, 15) bpm in the NAF and 10 (3, 18) bpm in the SAN groups. Baseline QTc was 382 (95% CI 374, 390) ms in the NAF, 378 (363, 393) ms in the SAN and 392 (367, 417) ms in the CAN groups (p = 0.31). QTc in all groups lengthened comparably with adrenaline infusion. The longest QTc was 444 (422, 463) ms (NAF), 422 (402, 437) ms (SAN) and 470 (402, 519) ms (CAN) (p = 0.09). T wave amplitude and T wave symmetry ratio decreased and the maximum decrease occurred earlier, at lower infused adrenaline concentrations in the CAN group compared with NAF and SAN groups. AUC for the symmetry ratio was different across the groups and was lowest in the CAN group (p = 0.04). Plasma adrenaline rose and potassium fell comparably in all groups. CONCLUSIONS/INTERPRETATION Participants with CAN showed abnormal repolarisation in some measures at lower adrenaline concentrations. This may be due to denervation adrenergic hypersensitivity. Such individuals may be at greater risk of cardiac arrhythmias in response to physiological sympathoadrenal challenges such as stress or hypoglycaemia.
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Affiliation(s)
- Alan Bernjak
- Department of Oncology & Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield, UK
- INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK
| | - Elaine Chow
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
- Department of Medicine and Therapeutics, the Chinese University of Hong Kong, Hong Kong, China
| | - Emma J Robinson
- Department of Oncology & Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield, UK
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Jenny Freeman
- Leeds Institute of Life Sciences, University of Leeds, Leeds, UK
| | - Jefferson L B Marques
- Department of Oncology & Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield, UK
- Institute of Biomedical Engineering, Department of Electrical and Electronic Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil
| | - Ian A Macdonald
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - Paul J Sheridan
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Simon R Heller
- Department of Oncology & Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield, UK.
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK.
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Iqbal A, Prince LR, Novodvorsky P, Bernjak A, Thomas MR, Birch L, Lambert D, Kay LJ, Wright FJ, Macdonald IA, Jacques RM, Storey RF, McCrimmon RJ, Francis S, Heller SR, Sabroe I. Effect of Hypoglycemia on Inflammatory Responses and the Response to Low-Dose Endotoxemia in Humans. J Clin Endocrinol Metab 2019; 104:1187-1199. [PMID: 30252067 PMCID: PMC6391720 DOI: 10.1210/jc.2018-01168] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/19/2018] [Indexed: 12/20/2022]
Abstract
CONTEXT Hypoglycemia is emerging as a risk for cardiovascular events in diabetes. We hypothesized that hypoglycemia activates the innate immune system, which is known to increase cardiovascular risk. OBJECTIVE To determine whether hypoglycemia modifies subsequent innate immune system responses. DESIGN AND SETTING Single-blinded, prospective study of three independent parallel groups. PARTICIPANTS AND INTERVENTIONS Twenty-four healthy participants underwent either a hyperinsulinemic-hypoglycemic (2.5 mmol/L), euglycemic (6.0 mmol/L), or sham-saline clamp (n = 8 for each group). After 48 hours, all participants received low-dose (0.3 ng/kg) intravenous endotoxin. MAIN OUTCOME MEASURES We studied in-vivo monocyte mobilization and monocyte-platelet interactions. RESULTS Hypoglycemia increased total leukocytes (9.98 ± 1.14 × 109/L vs euglycemia 4.38 ± 0.53 × 109/L, P < 0.001; vs sham-saline 4.76 ± 0.36 × 109/L, P < 0.001) (mean ± SEM), mobilized proinflammatory intermediate monocytes (42.20 ± 7.52/μL vs euglycemia 20.66 ± 3.43/μL, P < 0.01; vs sham-saline 26.20 ± 3.86/μL, P < 0.05), and nonclassic monocytes (36.16 ± 4.66/μL vs euglycemia 12.72 ± 2.42/μL, P < 0.001; vs sham-saline 19.05 ± 3.81/μL, P < 0.001). Following hypoglycemia vs euglycemia, platelet aggregation to agonist (area under the curve) increased (73.87 ± 7.30 vs 52.50 ± 4.04, P < 0.05) and formation of monocyte-platelet aggregates increased (96.05 ± 14.51/μL vs 49.32 ± 6.41/μL, P < 0.05). Within monocyte subsets, hypoglycemia increased aggregation of intermediate monocytes (10.51 ± 1.42/μL vs euglycemia 4.19 ± 1.08/μL, P < 0.05; vs sham-saline 3.81± 1.42/μL, P < 0.05) and nonclassic monocytes (9.53 ± 1.08/μL vs euglycemia 2.86 ± 0.72/μL, P < 0.01; vs sham-saline 3.08 ± 1.01/μL, P < 0.05), with platelets compared with controls. Hypoglycemia led to greater leukocyte mobilization in response to subsequent low-dose endotoxin challenge (10.96 ± 0.97 vs euglycemia 8.21 ± 0.85 × 109/L, P < 0.05). CONCLUSIONS Hypoglycemia mobilizes monocytes, increases platelet reactivity, promotes interaction between platelets and proinflammatory monocytes, and potentiates the subsequent immune response to endotoxin. These changes may contribute to increased cardiovascular risk observed in people with diabetes.
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Affiliation(s)
- Ahmed Iqbal
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - Lynne R Prince
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Peter Novodvorsky
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom
| | - Alan Bernjak
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom
- INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Mark R Thomas
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Lewis Birch
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Danielle Lambert
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Linda J Kay
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Fiona J Wright
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Ian A Macdonald
- MRC/ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research Nottingham Biomedical Research Centre, Nottingham, United Kingdom
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University Nottingham, Nottingham, United Kingdom
| | - Richard M Jacques
- School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom
| | - Robert F Storey
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, University of Dundee, Dundee, United Kingdom
| | - Sheila Francis
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Simon R Heller
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom
- Correspondence and Reprint Requests: Simon R. Heller, DM, Department of Oncology and Metabolism, University of Sheffield, Medical School, Beech Hill Road, Sheffield S10 2RX, United Kingdom. E-mail:
| | - Ian Sabroe
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, United Kingdom
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Novodvorsky P, Bernjak A, Robinson EJ, Iqbal A, Macdonald IA, Jacques RM, Marques JLB, Sheridan PJ, Heller SR. Salbutamol-induced electrophysiological changes show no correlation with electrophysiological changes during hyperinsulinaemic-hypoglycaemic clamp in young people with Type 1 diabetes. Diabet Med 2018; 35:1264-1272. [PMID: 29682793 PMCID: PMC6099209 DOI: 10.1111/dme.13650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/16/2018] [Indexed: 12/01/2022]
Abstract
AIMS Hypoglycaemia causes QT-interval prolongation and appears pro-arrhythmogenic. Salbutamol, a β2 -adrenoreceptor agonist also causes QT-interval prolongation. We hypothesized that the magnitude of electrophysiological changes induced by salbutamol and hypoglycaemia might relate to each other and that salbutamol could be used as a non-invasive screening tool for predicting an individual's electrophysiological response to hypoglycaemia. METHODS Eighteen individuals with Type 1 diabetes were administered 2.5 mg of nebulized salbutamol. Participants then underwent a hyperinsulinaemic-hypoglycaemic clamp (2.5 mmol/l for 1 h). During both experiments, heart rate and serum potassium (and catecholamines during the clamp) were measured and a high-resolution electrocardiogram (ECG) was recorded at pre-set time points. Cardiac repolarization was measured by QT-interval duration adjusted for heart rate (QTc ), T-wave amplitude (Tamp ), T-peak to T-end interval duration (Tp Tend ) and T-wave area symmetry (Tsym ). The maximum changes vs. baseline in both experiments were assessed for their linear dependence. RESULTS Salbutamol administration caused QTc and Tp Tend prolongation and a decrease in Tamp and Tsym . Hypoglycaemia caused increased plasma catecholamines, hypokalaemia, QTc and Tp Tend prolongation, and a decrease in Tamp and Tsym . No significant correlations were found between maximum changes in QTc [r = 0.15, 95% confidence interval (95% CI) -0.341 to 0.576; P = 0.553), Tp Tend (r = 0.075, 95% CI -0.406 to 0.524; P = 0.767), Tsym (r = 0.355, 95% CI -0.132 to 0.706; P = 0.149) or Tamp (r = 0.148, 95% CI -0.347 to 0.572; P = 0.558) in either experiment. CONCLUSIONS Both hypoglycaemia and salbutamol caused pro-arrhythmogenic electrophysiological changes in people with Type 1 diabetes but were not related in any given individual. Salbutamol does not appear useful in assessing an individual's electrophysiological response to hypoglycaemia.
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Affiliation(s)
- P. Novodvorsky
- Department of Oncology and MetabolismUniversity of Sheffield
- Sheffield Teaching Hospitals NHS Foundation Trust
| | - A. Bernjak
- Department of Oncology and MetabolismUniversity of Sheffield
- INSIGNEO Institute for in silico Medicine
| | - E. J. Robinson
- Department of Oncology and MetabolismUniversity of Sheffield
- Sheffield Teaching Hospitals NHS Foundation Trust
| | - A. Iqbal
- Department of Oncology and MetabolismUniversity of Sheffield
- Sheffield Teaching Hospitals NHS Foundation Trust
- Department of Infection, Immunity and Cardiovascular DiseaseUniversity of SheffieldSheffield
| | | | - R. M. Jacques
- School of Health and Related ResearchUniversity of SheffieldSheffieldUK
| | | | | | - S. R. Heller
- Department of Oncology and MetabolismUniversity of Sheffield
- Sheffield Teaching Hospitals NHS Foundation Trust
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Ticcinelli V, Stankovski T, Iatsenko D, Bernjak A, Bradbury AE, Gallagher AR, Clarkson PBM, McClintock PVE, Stefanovska A. Coherence and Coupling Functions Reveal Microvascular Impairment in Treated Hypertension. Front Physiol 2017; 8:749. [PMID: 29081750 PMCID: PMC5645539 DOI: 10.3389/fphys.2017.00749] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 09/14/2017] [Indexed: 01/02/2023] Open
Abstract
The complex interactions that give rise to heart rate variability (HRV) involve coupled physiological oscillators operating over a wide range of different frequencies and length-scales. Based on the premise that interactions are key to the functioning of complex systems, the time-dependent deterministic coupling parameters underlying cardiac, respiratory and vascular regulation have been investigated at both the central and microvascular levels. Hypertension was considered as an example of a globally altered state of the complex dynamics of the cardiovascular system. Its effects were established through analysis of simultaneous recordings of the electrocardiogram (ECG), respiratory effort, and microvascular blood flow [by laser Doppler flowmetry (LDF)]. The signals were analyzed by methods developed to capture time-dependent dynamics, including the wavelet transform, wavelet-based phase coherence, non-linear mode decomposition, and dynamical Bayesian inference, all of which can encompass the inherent frequency and coupling variability of living systems. Phases of oscillatory modes corresponding to the cardiac (around 1.0 Hz), respiratory (around 0.25 Hz), and vascular myogenic activities (around 0.1 Hz) were extracted and combined into two coupled networks describing the central and peripheral systems, respectively. The corresponding spectral powers and coupling functions were computed. The same measurements and analyses were performed for three groups of subjects: healthy young (Y group, 24.4 ± 3.4 y), healthy aged (A group, 71.1 ± 6.6 y), and aged treated hypertensive patients (ATH group, 70.3 ± 6.7 y). It was established that the degree of coherence between low-frequency oscillations near 0.1 Hz in blood flow and in HRV time series differs markedly between the groups, declining with age and nearly disappearing in treated hypertension. Comparing the two healthy groups it was found that the couplings to the cardiac rhythm from both respiration and vascular myogenic activity decrease significantly in aging. Comparing the data from A and ATH groups it was found that the coupling from the vascular myogenic activity is significantly weaker in treated hypertension subjects, implying that the mechanisms of microcirculation are not completely restored by current anti-hypertension medications.
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Affiliation(s)
| | - Tomislav Stankovski
- Physics Department, Lancaster University, Lancaster, United Kingdom
- Faculty of Medicine, Saints Cyril and Methodius University of Skopje, Skopje, Macedonia
| | - Dmytro Iatsenko
- Physics Department, Lancaster University, Lancaster, United Kingdom
- Deutsche Bank AG, London, United Kingdom
| | - Alan Bernjak
- Physics Department, Lancaster University, Lancaster, United Kingdom
- Department of Oncology & Metabolism, University of Sheffield, Sheffield, United Kingdom
| | - Adam E. Bradbury
- Physics Department, Lancaster University, Lancaster, United Kingdom
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Chang ETY, Bernjak A, Nelson T, Smith G, Lee J, Clayton RH. 30Optimising the predictive capability of a mathematical model of AF progression using cardiac device data. Europace 2017. [DOI: 10.1093/europace/eux283.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Novodvorsky P, Bernjak A, Chow E, Iqbal A, Sellors L, Williams S, Fawdry RA, Parekh B, Jacques RM, Marques JLB, Sheridan PJ, Heller SR. Diurnal Differences in Risk of Cardiac Arrhythmias During Spontaneous Hypoglycemia in Young People With Type 1 Diabetes. Diabetes Care 2017; 40:655-662. [PMID: 28213374 DOI: 10.2337/dc16-2177] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/23/2017] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Hypoglycemia may exert proarrhythmogenic effects on the heart via sympathoadrenal stimulation and hypokalemia. Hypoglycemia-induced cardiac dysrhythmias are linked to the "dead-in-bed syndrome," a rare but devastating condition. We examined the effect of nocturnal and daytime clinical hypoglycemia on electrocardiogram (ECG) in young people with type 1 diabetes. RESEARCH DESIGN AND METHODS Thirty-seven individuals with type 1 diabetes underwent 96 h of simultaneous ambulatory ECG and blinded continuous interstitial glucose monitoring (CGM) while symptomatic hypoglycemia was recorded. Frequency of arrhythmias, heart rate variability, and cardiac repolarization were measured during hypoglycemia and compared with time-matched euglycemia during night and day. RESULTS A total of 2,395 h of simultaneous ECG and CGM recordings were obtained; 159 h were designated hypoglycemia and 1,355 h euglycemia. A median duration of nocturnal hypoglycemia of 60 min (interquartile range 40-135) was longer than daytime hypoglycemia of 44 min (30-70) (P = 0.020). Only 24.1% of nocturnal and 51.0% of daytime episodes were symptomatic. Bradycardia was more frequent during nocturnal hypoglycemia compared with matched euglycemia (incident rate ratio [IRR] 6.44 [95% CI 6.26, 6.63], P < 0.001). During daytime hypoglycemia, bradycardia was less frequent (IRR 0.023 [95% CI 0.002, 0.26], P = 0.002) and atrial ectopics more frequent (IRR 2.29 [95% CI 1.19, 4.39], P = 0.013). Prolonged QTc, T-peak to T-end interval duration, and decreased T-wave symmetry were detected during nocturnal and daytime hypoglycemia. CONCLUSIONS Asymptomatic hypoglycemia was common. We identified differences in arrhythmic risk and cardiac repolarization during nocturnal versus daytime hypoglycemia in young adults with type 1 diabetes. Our data provide further evidence that hypoglycemia is proarrhythmogenic.
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Affiliation(s)
- Peter Novodvorsky
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K
| | - Alan Bernjak
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, U.K
| | - Elaine Chow
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K
| | - Ahmed Iqbal
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K
| | - Lianne Sellors
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K
| | - Scott Williams
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K
| | - Robert A Fawdry
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K
| | - Bhavin Parekh
- Department of Biomedical Science, University of Sheffield, Sheffield, U.K
| | - Richard M Jacques
- School of Health and Related Research, University of Sheffield, Sheffield, U.K
| | | | - Paul J Sheridan
- Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K
| | - Simon R Heller
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K. .,Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K
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Chow E, Bernjak A, Walkinshaw E, Lubina-Solomon A, Freeman J, Macdonald IA, Sheridan PJ, Heller SR. Cardiac Autonomic Regulation and Repolarization During Acute Experimental Hypoglycemia in Type 2 Diabetes. Diabetes 2017; 66:1322-1333. [PMID: 28137792 PMCID: PMC5860266 DOI: 10.2337/db16-1310] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/25/2017] [Indexed: 02/03/2023]
Abstract
Hypoglycemia is associated with increased cardiovascular mortality in trials of intensive therapy in type 2 diabetes mellitus (T2DM). We previously observed an increase in arrhythmias during spontaneous prolonged hypoglycemia in patients with T2DM. We examined changes in cardiac autonomic function and repolarization during sustained experimental hypoglycemia. Twelve adults with T2DM and 11 age- and BMI-matched control participants without diabetes underwent paired hyperinsulinemic clamps separated by 4 weeks. Glucose was maintained at euglycemia (6.0 mmol/L) or hypoglycemia (2.5 mmol/L) for 1 h. Heart rate, blood pressure, and heart rate variability were assessed every 30 min and corrected QT intervals and T-wave morphology every 60 min. Heart rate initially increased in participants with T2DM but then fell toward baseline despite maintained hypoglycemia at 1 h accompanied by reactivation of vagal tone. In control participants, vagal tone remained depressed during sustained hypoglycemia. Participants with T2DM exhibited greater heterogeneity of repolarization during hypoglycemia as demonstrated by T-wave symmetry and principal component analysis ratio compared with control participants. Epinephrine levels during hypoglycemia were similar between groups. Cardiac autonomic regulation during hypoglycemia appears to be time dependent. Individuals with T2DM demonstrate greater repolarization abnormalities for a given hypoglycemic stimulus despite comparable sympathoadrenal responses. These mechanisms could contribute to arrhythmias during clinical hypoglycemic episodes.
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Affiliation(s)
- Elaine Chow
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K
| | - Alan Bernjak
- INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sheffield, U.K
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K
| | - Emma Walkinshaw
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K
| | | | - Jenny Freeman
- Leeds Institute of Health Sciences, University of Leeds, Leeds, U.K
| | - Ian A Macdonald
- School of Life Sciences, University of Nottingham, Nottingham, U.K
| | - Paul J Sheridan
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K
| | - Simon R Heller
- Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.
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11
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Kenwright DA, Bernjak A, Draegni T, Dzeroski S, Entwistle M, Horvat M, Kvandal P, Landsverk SA, McClintock PVE, Musizza B, Petrovčič J, Raeder J, Sheppard LW, Smith AF, Stankovski T, Stefanovska A. The discriminatory value of cardiorespiratory interactions in distinguishing awake from anaesthetised states: a randomised observational study. Anaesthesia 2015; 70:1356-68. [PMID: 26350998 PMCID: PMC4989441 DOI: 10.1111/anae.13208] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2015] [Indexed: 12/20/2022]
Abstract
Depth of anaesthesia monitors usually analyse cerebral function with or without other physiological signals; non‐invasive monitoring of the measured cardiorespiratory signals alone would offer a simple, practical alternative. We aimed to investigate whether such signals, analysed with novel, non‐linear dynamic methods, would distinguish between the awake and anaesthetised states. We recorded ECG, respiration, skin temperature, pulse and skin conductivity before and during general anaesthesia in 27 subjects in good cardiovascular health, randomly allocated to receive propofol or sevoflurane. Mean values, variability and dynamic interactions were determined. Respiratory rate (p = 0.0002), skin conductivity (p = 0.03) and skin temperature (p = 0.00006) changed with sevoflurane, and skin temperature (p = 0.0005) with propofol. Pulse transit time increased by 17% with sevoflurane (p = 0.02) and 11% with propofol (p = 0.007). Sevoflurane reduced the wavelet energy of heart (p = 0.0004) and respiratory (p = 0.02) rate variability at all frequencies, whereas propofol decreased only the heart rate variability below 0.021 Hz (p < 0.05). The phase coherence was reduced by both agents at frequencies below 0.145 Hz (p < 0.05), whereas the cardiorespiratory synchronisation time was increased (p < 0.05). A classification analysis based on an optimal set of discriminatory parameters distinguished with 95% success between the awake and anaesthetised states. We suggest that these results can contribute to the design of new monitors of anaesthetic depth based on cardiovascular signals alone.
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Affiliation(s)
| | | | - T Draegni
- Oslo University Hospital, Ullevaal, Norway
| | - S Dzeroski
- Jožef Stefan Institute, Ljubljana, Slovenia
| | | | - M Horvat
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
| | - P Kvandal
- Oslo University Hospital, Ullevaal, Norway
| | | | | | - B Musizza
- Jožef Stefan Institute, Ljubljana, Slovenia
| | | | - J Raeder
- Oslo University Hospital, Ullevaal, Norway
| | | | - A F Smith
- Royal Lancaster Infirmary, Lancaster, UK
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12
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Chow E, Bernjak A, Williams S, Fawdry RA, Hibbert S, Freeman J, Sheridan PJ, Heller SR. Risk of cardiac arrhythmias during hypoglycemia in patients with type 2 diabetes and cardiovascular risk. Diabetes 2014; 63:1738-47. [PMID: 24757202 DOI: 10.2337/db13-0468] [Citation(s) in RCA: 272] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent trials of intensive glycemic control suggest a possible link between hypoglycemia and excess cardiovascular mortality in patients with type 2 diabetes. Hypoglycemia might cause arrhythmias through effects on cardiac repolarization and changes in cardiac autonomic activity. Our aim was to study the risk of arrhythmias during spontaneous hypoglycemia in type 2 diabetic patients with cardiovascular risk. Twenty-five insulin-treated patients with type 2 diabetes and a history of cardiovascular disease or two or more risk factors underwent simultaneous continuous interstitial glucose and ambulatory electrocardiogram monitoring. Frequency of arrhythmias, heart rate variability, and markers of cardiac repolarization were compared between hypoglycemia and euglycemia and between hyperglycemia and euglycemia matched for time of day. There were 134 h of recording at hypoglycemia, 65 h at hyperglycemia, and 1,258 h at euglycemia. Bradycardia and atrial and ventricular ectopic counts were significantly higher during nocturnal hypoglycemia compared with euglycemia. Arrhythmias were more frequent during nocturnal versus daytime hypoglycemia. Excessive compensatory vagal activation after the counterregulatory phase may account for bradycardia and associated arrhythmias. QT intervals, corrected for heart rate, >500 ms and abnormal T-wave morphology were observed during hypoglycemia in some participants. Hypoglycemia, frequently asymptomatic and prolonged, may increase the risk of arrhythmias in patients with type 2 diabetes and high cardiovascular risk. This is a plausible mechanism that could contribute to increased cardiovascular mortality during intensive glycemic therapy.
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Affiliation(s)
- Elaine Chow
- Department of Cardiovascular Science, University of Sheffield, Sheffield, U.K
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13
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Iatsenko D, Bernjak A, Stankovski T, Shiogai Y, Owen-Lynch PJ, Clarkson PBM, McClintock PVE, Stefanovska A. Evolution of cardiorespiratory interactions with age. Philos Trans A Math Phys Eng Sci 2013; 371:20110622. [PMID: 23858485 PMCID: PMC4042892 DOI: 10.1098/rsta.2011.0622] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We describe an analysis of cardiac and respiratory time series recorded from 189 subjects of both genders aged 16-90. By application of the synchrosqueezed wavelet transform, we extract the respiratory and cardiac frequencies and phases with better time resolution than is possible with the marked events procedure. By treating the heart and respiration as coupled oscillators, we then apply a method based on Bayesian inference to find the underlying coupling parameters and their time dependence, deriving from them measures such as synchronization, coupling directionality and the relative contributions of different mechanisms. We report a detailed analysis of the reconstructed cardiorespiratory coupling function, its time evolution and age dependence. We show that the direct and indirect respiratory modulations of the heart rate both decrease with age, and that the cardiorespiratory coupling becomes less stable and more time-variable.
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Affiliation(s)
- D. Iatsenko
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
- e-mail:
| | - A. Bernjak
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
- Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - T. Stankovski
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
| | - Y. Shiogai
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
| | - P. J. Owen-Lynch
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster LA1 4YQ, UK
| | - P. B. M. Clarkson
- Cardiology Department, Raigmore Hospital, Old Perth Road, Inverness IV2 3UJ, UK
| | | | - A. Stefanovska
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
- Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
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14
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Bernjak A, Cui J, Iwase S, Mano T, Stefanovska A, Eckberg DL. Human sympathetic outflows to skin and muscle target organs fluctuate concordantly over a wide range of time-varying frequencies. J Physiol 2011; 590:363-75. [PMID: 22063627 DOI: 10.1113/jphysiol.2011.214528] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Frequency-domain analyses of simultaneously recorded skin and muscle sympathetic nerve activities may yield unique information on otherwise obscure central processes governing human neural outflows. We used wavelet transform and wavelet phase coherence methods to analyse integrated skin and muscle sympathetic nerve activities and haemodynamic fluctuations, recorded from nine healthy supine young men. We tested two null hypotheses: (1) that human skin and muscle sympathetic nerve activities oscillate congruently; and (2) that whole-body heating affects these neural outflows and their haemodynamic consequences in similar ways. Measurements included peroneal nerve skin and tibial nerve muscle sympathetic activities; the electrocardiogram; finger photoplethysmographic arterial pressure; respiration (controlled at 0.25 Hz, and registered with a nasal thermistor); and skin temperature, sweating, and laser-Doppler skin blood flow. We made recordings at ∼27°C, for ∼20 min, and then during room temperature increases to ∼38°C, over 35 min. We analysed data with a wavelet transform, using the Morlet mother wavelet and wavelet phase coherence, to determine the frequencies and coherences of oscillations over time. At 27°C, skin and muscle nerve activities oscillated coherently, at ever-changing frequencies between 0.01 and the cardiac frequency (∼1 Hz). Heating significantly augmented oscillations of skin sympathetic nerve activity and skin blood flow, arterial pressure, and R-R intervals, over a wide range of low frequencies, and modestly reduced coordination between skin and muscle sympathetic oscillations. These results suggest that human skin and muscle sympathetic motoneurones are similarly entrained by external influences, including those of arterial baroreceptors, respiration, and other less well-defined brainstem oscillators. Our study provides strong support for the existence of multiple, time-varying central sympathetic neural oscillators in human subjects.
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Affiliation(s)
- Alan Bernjak
- Ekholmen, 8728 Dick Woods Road, Afton, VA 22920, USA
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15
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Bernjak A, Deitrick G, Bauman W, Stefanovska A, Tuckman J. Basal sympathetic activity to the microcirculation in tetraplegic man revealed by wavelet transform of laser Doppler flowmetry. Microvasc Res 2011; 81:313-8. [DOI: 10.1016/j.mvr.2011.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 01/14/2011] [Accepted: 01/14/2011] [Indexed: 10/18/2022]
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Abstract
The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances.
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Affiliation(s)
- Alan Bernjak
- Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, 1000 Ljubljana, Slovenia. Physics Department, Lancaster University, LA1 4YB, UK
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17
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Bernjak A, Clarkson P, McClintock P, Stefanovska A. Low-frequency blood flow oscillations in congestive heart failure and after beta1-blockade treatment. Microvasc Res 2008; 76:224-32. [PMID: 18721820 PMCID: PMC2666799 DOI: 10.1016/j.mvr.2008.07.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 07/22/2008] [Accepted: 07/23/2008] [Indexed: 11/20/2022]
Abstract
Laser Doppler flowmetry (LDF) of forearm skin blood flow, combined with iontophoretically-administered acetylcholine and sodium nitroprusside and wavelet spectral analysis, was used for noninvasive evaluation of endothelial function in 17 patients newly diagnosed with New York Heart Association class II-III congestive heart failure (CHF). After 20+/-10 weeks' treatment with a beta(1)-blocker (Bisoprolol), the measurements were repeated. Measurements were also made on an age- and sex-matched group of healthy controls (HC). In each case data were recorded for 30 min. In HC, the difference in absolute spectral amplitude of LDF oscillations between the two vasodilators manifests in the frequency interval 0.005-0.0095 Hz (p<0.01); this difference is initially absent in patients with CHF, but appears following the beta(1)-blocker treatment (p<0.01). For HC, the difference between the two vasodilators also manifests in normalised spectral amplitude in 0.0095-0.021 Hz (p<0.05). This latter difference is absent in CHF patients and is unchanged by treatment with beta(1)-blockers. It is concluded that there are two oscillatory skin blood flow components associated with endothelial function. Both are reduced in CHF. Activity in the lower frequency interval is restored by beta(1)-blocker treatment, confirming the association between CHF and endothelial dysfunction but suggesting the involvement of two distinct mechanisms.
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Affiliation(s)
- A. Bernjak
- Faculty of Electrical Engineering, University of Ljubljana, Slovenia
- Physics Department, Lancaster University, LA1 4YB, UK
| | - P.B.M. Clarkson
- Cardiology Department, Royal Lancaster Infirmary, LA1 4RP, UK
| | | | - A. Stefanovska
- Faculty of Electrical Engineering, University of Ljubljana, Slovenia
- Physics Department, Lancaster University, LA1 4YB, UK
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Abstract
Spectral analysis of microvascular laser Doppler flowmetry time series is performed to resolve their complex dynamics. The method of analysis should be carefully chosen such that as much information as possible of the signal is obtained. Conventional Fourier transform and short-time Fourier transform are compared with wavelet analysis to resolve several oscillatory components on a wide frequency interval. Wavelet transform with the Morlet mother wavelet is shown to have an advantage of adjustable window length as it detects each frequency with a window of a corresponding length. In this way good localization in time and frequency is provided. Low and high frequencies can be resolved and their variations traced in time. This is of crucial importance in analysis of oscillations in LDF signals and studies of their physiological origin as well as their changes in health and disease.
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Affiliation(s)
- Alan Bernjak
- Nonlinear Dynamics and Synergetics Group, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
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Azman-Juvan K, Bernjak A, Urbancic-Rovan V, Stefanovska A, Stajer D. Skin blood flow and its oscillatory components in patients with acute myocardial infarction. J Vasc Res 2007; 45:164-72. [PMID: 17962720 DOI: 10.1159/000110208] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 08/12/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Laser Doppler flowmetry (LDF) was used to determine the influence of acute myocardial infarction (AMI) and of successful reperfusion treatment on basal skin blood flow and its oscillatory components. METHODS Skin LDF was performed on all extremities in 58 patients 4-9 days after AMI (Killip class I), and in 71 healthy age- and sex-matched controls. Wavelet analysis was applied to evaluate oscillatory components within the interval 0.005-2 Hz. RESULTS AMI patients had reduced mean flow (p < 0.01) and oscillatory components (p < 0.04) in all extremities. Reperfused (n = 40), compared to nonreperfused (n = 18), patients had higher mean flow and total spectral amplitude at all recording points. The difference was statistically significant only in legs (group median LDF in the left leg was 9.68 AU for reperfused and 5.71 AU for nonreperfused patients, p < 0.04, and 11.47 and 4.24 AU in the right leg, p < 0.01). Reperfused patients had significantly higher total spectral amplitude in both legs (p < 0.04). CONCLUSIONS In AMI patients, reduced skin blood flow and its oscillatory components may reflect ongoing neurohumoral activation despite absence of clinically apparent heart failure. The reduction of blood flow and its oscillatory components was larger in nonreperfused AMI patients, although they had a comparable left ventricular function.
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Affiliation(s)
- Katja Azman-Juvan
- Department of Intensive Internal Medicine, University Medical Center Ljubljana, Ljubljana, Slovenia.
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Landsverk SA, Kvandal P, Bernjak A, Stefanovska A, Kirkeboen KA. The Effects of General Anesthesia on Human Skin Microcirculation Evaluated by Wavelet Transform. Anesth Analg 2007; 105:1012-9, table of contents. [PMID: 17898381 DOI: 10.1213/01.ane.0000281932.09660.96] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Time-frequency analysis of the laser Doppler flowmetry signal, using wavelet transform, shows periodic oscillations at five characteristic frequencies related to the heart (0.6-2 Hz), respiration (0.15-0.6 Hz), myogenic activity in the vessel wall (0.052-0.15 Hz), sympathetic activity (0.021-0.052 Hz), and very slow oscillations (0.0095-0.021), which can be modulated by the endothelium-dependent vasodilator acetylcholine. We hypothesized that wavelet transform of laser Doppler flowmetry signals could detect changes in the microcirculation induced by general anesthesia, such as alterations in vasomotion and sympathetic activity. METHODS Eleven patients undergoing faciomaxillary surgery were included. Skin microcirculation was measured on the lower forearm with laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside before and during general anesthesia with propofol, fentanyl, and midazolam. The laser Doppler flowmetry signals were analyzed using wavelet transform. RESULTS There were significant reductions in spectral amplitudes in the 0.0095-0.021 (P < 0.01), the 0.021-0.052 (P < 0.001), and the 0.052-0.15 Hz frequency interval (P < 0.01) and a significant increase in the 0.15-0.6 Hz frequency interval. General anesthesia had no effect on the difference between acetylcholine and sodium nitroprusside on relative amplitudes in the 0.0095-0.021 Hz frequency interval (P < 0.001). CONCLUSION General anesthesia reduces the oscillatory components of the perfusion signal related to sympathetic, myogenic activity and the component modulated by the endothelium. However, the iontophoretic data did not reveal a specific effect on the endothelium. The increase in the 0.15-0.6 Hz interval is related to the effect of mechanical ventilation.
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Benedicic M, Bernjak A, Stefanovska A, Bosnjak R. Continuous wavelet transform of laser-Doppler signals from facial microcirculation reveals vasomotion asymmetry. Microvasc Res 2007; 74:45-50. [PMID: 17395216 DOI: 10.1016/j.mvr.2007.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 02/02/2007] [Accepted: 02/19/2007] [Indexed: 10/23/2022]
Abstract
Facial laser Doppler flux (FLDF) consists of a mean value and complex oscillatory components called vasomotion. Vasomotion can be expressed as spectral amplitudes (SA) after the application of continuous wavelet transform. Vasomotion is influenced by cardiac activity (frequency interval I), respiration (interval II), intrinsic myogenic activity (interval III), neural mechanisms (interval IV) and endothelial mechanisms (intervals V and VI). Asymmetry of FLDF mean value was previously documented and hereby we present homogeneity assessment for FLDF vasomotion. Mean FLDF (p<0.001), total SA (p<0.001) and SA within frequency intervals I-VI were significantly higher in both cheeks compared to forehead. Total SA (p=0.009) and SA within frequency intervals I (p=0.041), II (p=0.005), III (p=0.009), IV (p=0.001) and V (p=0.036) were significantly higher in right than in left forehead. Human face is a heterogeneous microvascular region. Angiographic characteristics of deep horizontal sub-dermal plexus, endothelial and vascular smooth muscle cell heterogeneity, and plasticity of the microvasculature, autonomic asymmetry and facial neuropsychological asymmetry are possible causes of microvascular asymmetry. The origin and significance of microvascular imbalance need to be elucidated further.
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Affiliation(s)
- Mitja Benedicic
- Department of Neurosurgery, University Medical Center, Zaloska 2, 1525 Ljubljana, Slovenia.
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Urbancic-Rovan V, Meglic B, Stefanovska A, Bernjak A, Azman-Juvan K, Kocijancic A. Incipient cardiovascular autonomic imbalance revealed by wavelet analysis of heart rate variability in Type 2 diabetic patients. Diabet Med 2007; 24:18-26. [PMID: 17227320 DOI: 10.1111/j.1464-5491.2007.02019.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Incipient cardiovascular autonomic imbalance is not readily diagnosed by conventional methods. Spectral analysis of heart rate variability (HRV) by wavelet transform (WT) was used to measure cardiovascular autonomic function in patients with Type 2 diabetes. METHODS Thirty-two diabetic patients without (D), 26 with cardiovascular autonomic neuropathy (DAN) and 72 control subjects (C) participated. A 30-min HRV time series was analysed by wavelet transformation and four characteristic frequency intervals were defined: I (0.0095-0.021 Hz), II (0.021-0.052 Hz), III (0.052-0.145 Hz) and IV (0.145-0.6 Hz). RESULTS When compared with C, in both D and DAN the normalized power and amplitude of interval II were increased and of interval IV decreased, resulting in a significantly higher II/IV ratio. Furthermore, in DAN the normalized power and amplitude of interval I were increased and of interval III decreased when compared with the D and C groups. The diabetic patients were divided in two equal subgroups according to HbA(1c) < 8.0% and >or= 8.0%. In the subgroup with HbA(1c) >or= 8.0%, normalized power in interval II was significantly higher and in interval IV significantly lower than in the subgroup with HbA(1c) < 8.0%. In D, but not in DAN patients prescribed ACE inhibitors, the absolute amplitude and power of oscillations were significantly higher than in patients not taking ACE inhibitor therapy. CONCLUSIONS Patients with diabetes have increased sympathetic and decreased parasympathetic cardiac activity regardless of the presence of autonomic neuropathy. Glycaemic control and treatment with ACE inhibitors may favourably influence HRV in diabetic patients without autonomic neuropathy.
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Affiliation(s)
- V Urbancic-Rovan
- Department of Endocrinology, Diabetes and Metabolic Diseases, University Medical Centre, University of Ljubljana, Ljubljana, Slovenia.
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Kvandal P, Landsverk SA, Bernjak A, Stefanovska A, Kvernmo HD, Kirkebøen KA. Low-frequency oscillations of the laser Doppler perfusion signal in human skin. Microvasc Res 2006; 72:120-7. [PMID: 16854436 DOI: 10.1016/j.mvr.2006.05.006] [Citation(s) in RCA: 231] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 04/20/2006] [Accepted: 05/15/2006] [Indexed: 11/26/2022]
Abstract
Spectral analysis of the laser Doppler flow (LDF) signal in the frequency interval from 0.0095-2.0 Hz reveals blood flow oscillations with frequencies around 1.0, 0.3, 0.1, 0.04 and 0.01 Hz. The heartbeat, the respiration, the intrinsic myogenic activity of vascular smooth muscle, the neurogenic activity of the vessel wall and the vascular endothelium influence these oscillations, respectively. The first aim of this study was to investigate if a slow oscillatory component could be detected in the frequency area below 0.0095 Hz of the human cutaneous blood perfusion signal. Unstimulated basal blood skin perfusion and enhanced perfusion during iontophoresis with the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) were measured in healthy male volunteers and the wavelet transform was computed. A low-frequency oscillation between 0.005 and 0.0095 Hz was found both during basal conditions and during iontophoresis with ACh and SNP. Iontophoresis with ACh increased the normalized amplitude to a greater extent than SNP (P = 0.001) indicating modulation by the vascular endothelium. To gain further insight into the mechanisms for this endothelium dependency, we inhibited nitric oxide (NO) synthesis with N(G)-monomethyl-L-arginine (L-NMMA) and prostaglandin (PG) synthesis by aspirin. L-NMMA did not affect the increased response to ACh vs. SNP iontophoresis in the 0.005-0.0095-Hz interval (P = 0.006) but abolished the difference in the 0.0095-0.021-Hz interval (P = 0.97). Aspirin did not affect the difference in response to ACh and SNP in either of the two frequency intervals. Thus, other endothelial mechanisms, such as endothelium-derived hyperpolarizing factor (EDHF), might be involved in the regulation of this sixth frequency interval (0.005-0.0095 Hz).
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Affiliation(s)
- Per Kvandal
- Department of Intensive Care Medicine, Ullevål University Hospital, 0407 Oslo, Norway.
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Landsverk SA, Kvandal P, Kjelstrup T, Benko U, Bernjak A, Stefanovska A, Kvernmo H, Kirkeboen KA. Human Skin Microcirculation after Brachial Plexus Block Evaluated by Wavelet Transform of the Laser Doppler Flowmetry Signal. Anesthesiology 2006; 105:478-84. [PMID: 16931979 DOI: 10.1097/00000542-200609000-00010] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Background
The skin microcirculation may be evaluated noninvasively by laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside. Wavelet transform of the perfusion signal shows periodic oscillations of five characteristic frequencies in the interval 0.0095-1.6 Hz. The aim of the current study was to investigate alterations in skin microcirculation induced by brachial plexus block, with emphasis on the periodic oscillations.
Methods
Healthy nonsmokers undergoing hand surgery (n = 13) were anesthetized with brachial plexus block, using bupivacaine, lidocaine, and epinephrine. Skin microcirculation was evaluated by laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside before and after brachial plexus block. Wavelet transform of the perfusion signal was performed. As a control group, 10 healthy nonsmokers were included.
Results
In the anesthetized arm, skin perfusion after brachial plexus block increased from 19 (12-30) to 24 (14-39) arbitrary units (P < 0.01). A significant increase was also seen in the contralateral arm from 17 (14-32) to 20 (14-42) arbitrary units (P < 0.01). After brachial plexus block, spectral analysis revealed a significant reduction in relative amplitude of the oscillatory components within the 0.0095- to 0.021- (P < 0.001) and 0.021- to 0.052-Hz (P < 0.001) intervals in the anesthetized arm.
Conclusion
Alterations in skin microcirculation induced by brachial plexus block can be evaluated by wavelet transform of the laser Doppler flowmetry signal. Brachial plexus block reduces the oscillatory components within the 0.0095- to 0.021- and 0.021- to 0.052-Hz intervals of the perfusion signal. These alterations are related to inhibition of sympathetic activity and a possible impairment of endothelial function.
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Affiliation(s)
- Svein A Landsverk
- Department of Anesthesiology, Ulleval University Hospital, Oslo, Norway.
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Urbancic-Rovan V, Bernjak A, Stefanovska A, Azman-Juvan K, Kocijancic A. Macro- and microcirculation in the lower extremities--possible relationship. Diabetes Res Clin Pract 2006; 73:166-73. [PMID: 16448716 DOI: 10.1016/j.diabres.2006.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2005] [Accepted: 01/04/2006] [Indexed: 10/25/2022]
Abstract
AIMS Impaired blood supply is a significant risk factor for diabetic foot ulceration and gangrene. A possible relationship between peripheral macroangiopathy and the spectral components of microvascular skin blood flow in the lower extremities was tested in diabetic patients (DP) and non-diabetic subjects (C). PATIENTS AND METHODS Basal skin blood flow (BSBF) was recorded for 30min at the right and left medial malleolus (predominantly nutritive capillary circulation) by laser Doppler flowmetry in 64 DP and 31 C. Its oscillatory components were analyzed using wavelet transform. Peripheral arterial obliterative disease (PAOD) was defined according to ankle/brachial index (ABI): PAOD+ (ABI<0.9: 21 DP, 12 C), PAOD- (ABI 0.91-1.3: 43 DP, 19 C). RESULTS No statistically significant differences in BSBF and its oscillatory components were observed between PAOD+ and PAOD-, neither in DP nor in C. In DP, the spectral component of microvascular flow associated with endothelial activity was in significant positive correlation with systolic pressures on brachial and dorsal pedal artery (p=0.001 and 0.010, respectively). CONCLUSIONS These results indicate that mean BSBF and its oscillatory components do not change with diabetic PAOD; however there is a strong correlation between systolic pressure and the oscillatory components of BSBF related to endothelial activity manifested in the frequency interval 0.0095-0.02Hz.
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Affiliation(s)
- Vilma Urbancic-Rovan
- University Medical Centre, Department of Endocrinology, Diabetes and Metabolic Diseases, Zaloska 7, 1525 Ljubljana, Slovenia.
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Urbancic-Rovan V, Stefanovska A, Bernjak A, Azman-Juvan K, Kocijancic A. Skin Blood Flow in the Upper and Lower Extremities of Diabetic Patients with and without Autonomic Neuropathy. J Vasc Res 2004; 41:535-45. [PMID: 15528936 DOI: 10.1159/000081810] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Accepted: 09/02/2004] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Microvascular blood flow in the human skin is subject to rhythmic variations reflecting the influence of heartbeat, respiration, intrinsic myogenic activity, neurogenic factors and endothelial activity. The aim of our study was to test the hypothesis that basal skin blood flow (BSBF) and its dynamic components differ (1) among diabetic patients without autonomic neuropathy and with it and healthy control subjects, and (2) among the upper and lower extremities. PATIENTS AND METHODS BSBF at four recording sites with predominantly nutritive capillary circulation (right and left caput ulnae, right and left medial malleolus) was measured by laser Doppler flowmetry in 25 diabetic patients without cardiovascular autonomic neuropathy (D), 18 neuropathic diabetic patients (DAN) and 36 healthy controls (C). Wavelet transform was applied to the laser Doppler signal. RESULTS In absolute terms, mean flow, mean amplitude of the total spectrum and mean amplitudes at all frequency intervals were highest in C, followed by DAN and lowest in D. However, these differences were statistically significant only in the left arm. Within all three groups, mean flow and spectral amplitudes were significantly higher in the arms than in the legs, besides there was a significant difference between the two arms in D. CONCLUSION We have confirmed the differences in BSBF among D, DAN and C, and demonstrated differences among the four recording sites which have not been previously described. The latter indicates an uneven progression of autonomic neuropathy and allows for speculation that the left arm is the latest to be affected.
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Affiliation(s)
- V Urbancic-Rovan
- Department of Endocrinology, Diabetes and Metabolic Diseases, University Medical Centre, Zaloska 7, SI-1525 Ljubljana, Slovenia.
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Abstract
Potential differences have been measured during transdermal iontophoresis in order to establish the effect of voltage, as opposed to current, on cutaneous blood flow. It is known that, even in the absence of drugs, the iontophoresis current can sometimes produce increased blood flow. The role of voltage in this process is studied through single-ended measurements (between electrode and body) of the potential difference during iontophoresis with 100-microA, 20-s current pulses through deionized water, saturated 20.4% NaCl solution, 1% acetylcholine, and 1% sodium nitroprusside. It is found that the voltage needed to deliver the current varied by orders of magnitudes less than the differences in the conductance of these different electrolytes, and it is concluded that, at least for the present current protocol, the voltage as such is not an important factor in increasing the blood flow.
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Bandrivskyy A, Bernjak A, McClintock P, Stefanovska A. Wavelet Phase Coherence Analysis: Application to Skin Temperature and Blood Flow. ACTA ACUST UNITED AC 2004. [DOI: 10.1023/b:care.0000025126.63253.43] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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