Diabetic autonomic neuropathy does not impede improvement in hypoglycaemia awareness in adults: Sub-study results from the HypoCOMPaSS trial.

Aims: Impaired awareness of hypoglycaemia (IAH) increases the risk of severe hypoglycaemia in people with type 1 diabetes mellitus (T1DM). IAH can be reversed through meticulous avoidance of hypoglycaemia. Diabetic autonomic neuropathy (DAN) has been proposed as an underlying mechanism contributing to IAH; however, data are inconsistent.

Hypoglycaemia combined with mild hypokalaemia reduces the heart rate and causes abnormal pacemaker activity in a computational model of a human sinoatrial cell.

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 , 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.

Cardiac arrhythmias and electrophysiologic responses during spontaneous hyperglycaemia in adults with type 1 diabetes mellitus.

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.

Nocturnal Hypoglycemia in Patients With Diabetes Discharged From ICUs: A Prospective Two-Center Cohort Study.

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.

Influence of cardiac autonomic neuropathy on cardiac repolarisation during incremental adrenaline infusion in type 1 diabetes.

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.

Effect of Hypoglycemia on Inflammatory Responses and the Response to Low-Dose Endotoxemia in Humans.

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.

Salbutamol-induced electrophysiological changes show no correlation with electrophysiological changes during hyperinsulinaemic-hypoglycaemic clamp in young people with Type 1 diabetes.

Aims: Hypoglycaemia causes QT-interval prolongation and appears pro-arrhythmogenic. Salbutamol, a β -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.

Coherence and Coupling Functions Reveal Microvascular Impairment in Treated Hypertension.

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.

Diurnal Differences in Risk of Cardiac Arrhythmias During Spontaneous Hypoglycemia in Young People With Type 1 Diabetes.

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.

Cardiac Autonomic Regulation and Repolarization During Acute Experimental Hypoglycemia in Type 2 Diabetes.

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.

The discriminatory value of cardiorespiratory interactions in distinguishing awake from anaesthetised states: a randomised observational study.

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.

Risk of cardiac arrhythmias during hypoglycemia in patients with type 2 diabetes and cardiovascular risk.

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.

Evolution of cardiorespiratory interactions with age.

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.

Human sympathetic outflows to skin and muscle target organs fluctuate concordantly over a wide range of time-varying frequencies.

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.

Basal sympathetic activity to the microcirculation in tetraplegic man revealed by wavelet transform of laser Doppler flowmetry.

Background: The 1984/86 published neurogram results showing only rare sympathetic nerve activity (SNA) to the muscles and skin in tetraplegia are still accepted. The present study by a different method attempted to confirm or deny those findings.

Methods And Results: The effect of basal SNA to the microcirculation of the feet and calf in 10 complete (AIS A) traumatic tetraplegic and 10 healthy age matched subjects were evaluated by wavelet transform of laser Doppler flowmetry (LDF) recordings.

Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry.

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.

Low-frequency blood flow oscillations in congestive heart failure and after beta1-blockade treatment.

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).

Importance of wavelet analysis in laser Doppler flowmetry time series.

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.

Skin blood flow and its oscillatory components in patients with acute myocardial infarction.

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.

The effects of general anesthesia on human skin microcirculation evaluated by wavelet transform.

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.

Continuous wavelet transform of laser-Doppler signals from facial microcirculation reveals vasomotion asymmetry.

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).

Incipient cardiovascular autonomic imbalance revealed by wavelet analysis of heart rate variability in Type 2 diabetic patients.

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.

Human skin microcirculation after brachial plexus block evaluated by wavelet transform of the laser Doppler flowmetry signal.

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.

Low-frequency oscillations of the laser Doppler perfusion signal in human skin.

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.

Macro- and microcirculation in the lower extremities--possible relationship.

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.