Mechanisms of abnormal cardiac repolarization during insulin-induced hypoglycemia

Norepinephrine mediates heart block during severe hypoglycemia in male rats

Hypoglycemia is common in people with type 1 diabetes. Sometimes, severe hypoglycemia can be fatal. The underlying mechanisms by which severe hypoglycemia can lead to death are unclear. The sympathetic nervous system is thought to be proarrhythmic. We hypothesized that norepinephrine is the main mediator of severe hypoglycemia-induced fatal cardiac arrhythmias. To test this hypothesis, adult, non-diabetic Sprague-Dawley rats were subjected to hyperinsulinemic-severe hypoglycemic clamps (3 h, 10-15 mg/dL) during two different experiments: (1) intracerebroventricular (ICV) norepinephrine (n = 26) or artificial cerebrospinal fluid (aCSF) (n = 20) infusion or (2) blockade of norepinephrine release by intraperitoneal reserpine (n = 20) or control (n = 29). In experiment 1, brain norepinephrine infusion during severe hypoglycemia led to a 2.5-fold increase in third-degree heart block and a 24% incidence of ST elevation compared to no ST elevation in aCSF controls. In experiment 2, reserpine successfully reduced plasma and cardiac norepinephrine levels. During severe hypoglycemia, reserpine completely prevented second and third-degree heart block and T wave increases, a marker of myocardial infarction, compared to controls. In conclusion, norepinephrine increases while reserpine, used to reduce norepinephrine nerve terminal release, reduces heart block and markers of myocardial infarction during severe hypoglycemia.

Genetic Causality between Type 1 Diabetes and Arrhythmia Identified by a Two-sample Mendelian Randomization Study

BACKGROUND

Clinical studies have shown that cardiovascular diseases in patients with type 1 diabetes (T1D) are often atypical or asymptomatic. The link between T1D and arrhythmia remains unclear. To infer causality between T1D and arrhythmia at the genetic level, we conducted a Mendelian randomization study through the genetic tools of T1D.

METHODS

In this study, we used genetic variables and summary statistics from genome-wide association studies of T1D and arrhythmia. Single nucleotide polymorphisms were selected based on the assumptions of instrumental variables. The inverse variance-weighted method was used as the primary analysis to summarize the causal effects between exposure and outcome. The weighted median and weighted mode methods were used as secondary methods. We tested for horizontal pleiotropy using the MR-Egger method and detected heterogeneity using the Q-test. A leave-one-out sensitivity analysis was performed. Scatter plots, forest plots, and funnel plots were used to visualize the results of the MR analysis.

RESULTS

In this study, we selected 28 T1D-related SNPs as instrumental variables. The IVW [odds ratio (OR) = 0.98, 95 % confidence interval (CI) = 0.97-1.00, P = 0.008], weighted median (OR = 0.98, 95 % CI = 0.96 - 0.99, P = 0.009), and weighted mode (OR = 0.98, 95 % CI = 0.96-0.99, P = 0.018) analysis methods suggested a causal effect of T1D on arrhythmia. The MR-Egger method indicated no horizontal pleiotropy (P = 0.649), and the Q-test showed no heterogeneity (IVW, P = 0.653).

CONCLUSIONS

Our MR analysis revealed a causal association between T1D and the development of arrhythmia, indicating that patients with T1D had a higher risk of arrhythmia.

Are the variations in ECG morphology associated to different blood glucose levels? implications for non-invasive glucose monitoring for T1D paediatric patients

AIMS

Recent clinical trials and real-world studies highlighted those variations in ECG waveforms and HRV recurrently occurred during hypoglycemic and hyperglycemic events in patients with diabetes. However, while several studies have been carried out for adult age, there is lack of evidence for paediatric patients. The main aim of the study is to identify the correlations of variations in ECG Morphology waveforms with blood glucose levels in a paediatric population.

METHODS

T1D paediatric patients who use CGM were enrolled. They wear an additional non-invasive wearable device for recording physiological data and respiratory rate. Glucose metrics, ECG parameters and HRV features were collected, and Wilcoxon rank-sum test and Spearman's correlation analysis were used to explore if different levels of blood glucose were associated to ECG morphological changes.

RESULTS

Results showed that hypoglycaemic events in paediatric patients with T1D are strongly associated with variations in ECG morphology and HRV.

CONCLUSIONS

Results showed the opportunity of using the ECG as a non-invasive adding instrument to monitor the hypoglycaemic events through the integration of the ECG continuous information with CGM data. This innovative approach represents a promising step forward in diabetes management, offering a more comprehensive and effective means of detecting and responding to critical changes in glucose levels.

Perioperative Glycemic Management in Cardiac Surgery: A Narrative Review

Diabetes and hyperglycemic events in cardiac surgical patients are associated with postoperative morbidity and mortality. The causes of dysglycemia, the abnormal fluctuations in blood glucose concentrations, in the perioperative period include surgical stress, surgical techniques, medications administered perioperatively, and patient factors. Both hyperglycemia and hypoglycemia lead to poor outcomes after cardiac surgery. While trying to control blood glucose concentration tightly for better postoperative outcomes, hypoglycemia is the main adverse event. Currently, there is no definite consensus on the optimum perioperative blood glucose concentration to be maintained in cardiac surgical patients. This review provides an overview of perioperative glucose homeostasis, the pathophysiology of dysglycemia, factors that affect glycemic control in cardiac surgery, and current practices for glycemic control in cardiac surgery.

Biochemical Toxicological Study of Insulin Overdose in Rats: A Forensic Perspective

Due to nonspecific pathological changes and the rapid degradation of insulin in postmortem blood samples, the identification of the cause of death during insulin overdose has always been a difficulty in forensic medicine. At present, there is a lack of studies on the toxicological changes and related mechanisms of an insulin overdose, and the specific molecular markers of insulin overdose are still unclear. In this study, an animal model of insulin overdose was established, and 24 SD rats were randomly divided into a control group, insulin overdose group, and a recovery group (n = 8). We detected the biochemical changes and analyzed the toxicological mechanism of an insulin overdose. The results showed that after insulin overdose, the rats developed irregular convulsions, Eclampsia, Opisthotonos, and other symptoms. The levels of glucose, glycogen, and C-peptide in the body decreased significantly, while the levels of lactate, insulin, and glucagon increased significantly. The decrease in plasma K+ was accompanied by the increase in skeletal muscle K+. The PI3K-AKT signaling pathway was significantly activated in skeletal muscle, and the translocation of GLUT4/Na+-K+-ATPase to sarcolemma was significantly increased. Rare glycogenic hepatopathy occurred in the recovery group after insulin overdose. Our study showed that insulin overdose also plays a role in skeletal muscle cells, mainly through the PI3K-Akt signaling pathway. Therefore, the detection of signaling pathway proteins of the skeletal muscle cell membrane GLUT4 and Na+-K+-ATPase has a certain auxiliary diagnostic value for forensic insulin overdose identification. Glycogen detection in the liver and skeletal muscle is important for the diagnosis of insulin overdose, but it still needs to be differentiated from other causes of death. Skeletal muscle has great potential for insulin detection, and the ratio of insulin to the C-peptide (I:C) can determine whether an exogenous insulin overdose is present.

Cardiac arrhythmia and hypoglycaemia in patients receiving haemodialysis with and without diabetes (the CADDY study): protocol for a Danish multicentre cohort study

INTRODUCTION

Patients receiving haemodialysis are at increased risk of arrhythmias and sudden cardiac death, but data on arrhythmia burden and the pathophysiology remain limited. Among potential risk factors, hypoglycaemia is proposed as a possible trigger of lethal arrhythmias. The development of implantable loop recorders (ILR) and continuous glucose monitoring (CGM) enables long-term continuous ECG and glycaemic monitoring. The current article presents the protocol of a study aiming to increase the understanding of arrhythmias and risk factors in patients receiving haemodialysis. The findings will provide a detailed exploration of the burden and nature of arrhythmias in these patients including the potential association between hypoglycaemia and arrhythmias.

METHODS AND ANALYSIS

The study is an investigator-initiated, prospective, multicentre cohort study recruiting 70 patients receiving haemodialysis: 35 with diabetes and 35 without diabetes. Participants are monitored with ILRs and CGM for 18 months follow-up. Data collection further includes a monthly collection of predialysis blood samples and dialysis parameters. The primary outcome is the presence of clinically significant arrhythmias defined as a composite of bradycardia, ventricular tachycardia, or ventricular fibrillation. Secondary outcomes include the characterisation of clinically significant arrhythmias and other arrhythmias, glycaemic characteristics, and mortality. The data analyses include an assessment of the association between arrhythmias and hypoglycaemia and hyperglycaemia, baseline clinical variables, and parameters related to kidney failure and the haemodialysis procedure.

ETHICS AND DISSEMINATION

The study has been approved by the Ethics Committee of the Capital Region of Denmark (H-20069767). The findings will be presented at national and international congresses as well as in international peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT04841304.

Brain Regulation of Cardiac Function during Hypoglycemia

Hypoglycemia occurs frequently in people with type 1 and type 2 diabetes. Hypoglycemia activates the counter-regulatory response. Besides peripheral glucose sensors located in the pancreas, mouth, gastrointestinal tract, portal vein, and carotid body, many brain regions also contain glucose-sensing neurons that detect this fall in glucose. The autonomic nervous system innervates the heart, and during hypoglycemia, can cause many changes. Clinical and animal studies have revealed changes in electrocardiograms during hypoglycemia. Cardiac repolarization defects (QTc prolongation) occur during moderate levels of hypoglycemia. When hypoglycemia is severe, it can be fatal. Cardiac arrhythmias are thought to be the major mediator of sudden death due to severe hypoglycemia. Both the sympathetic and parasympathetic nervous systems of the brain have been implicated in regulating these arrhythmias. Besides cardiac arrhythmias, hypoglycemia can have profound changes in the heart and most of these changes are exacerbated in the setting of diabetes. A better understanding of how the brain regulates cardiac changes during hypoglycemia will allow for better therapeutic intervention to prevent cardiovascular death associated with hypoglycemia in people with diabetes. The aim of this paper is to provide a narrative review of what is known in the field regarding how the brain regulates the heart during hypoglycemia.

Sodium-glucose cotransporter type 2 inhibitors and cardiac arrhythmias

The introduction of sodium-glucose cotransporter 2 (SGLT2) inhibitors as a new and effective class of therapeutic agents for type 2 diabetes (T2D) preventing the reabsorption of glucose in the kidneys and thus facilitating glucose excretion in the urine, but also as agents with cardiovascular benefits, particularly in patients with heart failure (HF), regardless of the diabetic status, has ushered in a new era in treating patients with T2D and/or HF. In addition, data have recently emerged indicating an antiarrhythmic effect of the SGLT2 inhibitors in patients with and without diabetes. Prospective studies, randomized controlled trials and meta-analyses have provided robust evidence for a protective and beneficial effect of these agents against atrial fibrillation, ventricular arrhythmias and sudden cardiac death. The antiarrhythmic mechanisms involved include reverse atrial and ventricular remodeling, amelioration of mitochondrial function, reduction of hypoglycemic episodes with their attendant arrhythmogenic effects, attenuated sympathetic nervous system activity, regulation of sodium and calcium homeostasis, and suppression of prolonged ventricular repolarization. These new data on antiarrhythmic actions of SGLT2 inhibitors are herein reviewed, potential mechanisms involved are discussed and pictorially illustrated, and treatment results on specific arrhythmias are described and tabulated.

Association of hypoglycaemia with the risks of arrhythmia and mortality in individuals with diabetes - a systematic review and meta-analysis

Background

Hypoglycaemia has been linked to an increased risk of cardiac arrhythmias by causing autonomic and metabolic alterations, which may be associated with detrimental outcomes in individuals with diabetes(IWD), such as cardiovascular diseases (CVDs) and mortality, especially in multimorbid or frail people. However, such relationships in this population have not been thoroughly investigated. For this reason, we conducted a systematic review and meta-analysis.

Methods

Relevant papers published on PubMed, Embase, Cochrane, Web of Knowledge, Scopus, and CINHAL complete from inception to December 22, 2022 were routinely searched without regard for language. All of the selected articles included odds ratio, hazard ratio, or relative risk statistics, as well as data for estimating the connection of hypoglycaemia with cardiac arrhythmia, CVD-induced death, or total death in IWD. Regardless of the heterogeneity assessed by the I2 statistic, pooled relative risks (RRs) and 95% confidence intervals (CI) were obtained using random-effects models.

Results

After deleting duplicates and closely evaluating all screened citations, we chose 60 studies with totally 5,960,224 participants for this analysis. Fourteen studies were included in the arrhythmia risk analysis, and 50 in the analysis of all-cause mortality. Hypoglycaemic patients had significantly higher risks of arrhythmia occurrence (RR 1.42, 95%CI 1.21-1.68), CVD-induced death (RR 1.59, 95% CI 1.24-2.04), and all-cause mortality (RR 1.68, 95% CI 1.49-1.90) compared to euglycaemic patients with significant heterogeneity.

Conclusion

Hypoglycaemic individuals are more susceptible to develop cardiac arrhythmias and die, but evidence of potential causal linkages beyond statistical associations must await proof by additional specifically well planned research that controls for all potential remaining confounding factors.

Effects of Hypoglycemia on Cardiovascular Function in Patients with Diabetes

Hypoglycemia is common in patients with type 1 and type 2 diabetes (T1D, T2D), treated with insulin or sulfonylureas, and has multiple short- and long-term clinical implications. Whether acute or recurrent, hypoglycemia significantly affects the cardiovascular system with the potential to cause cardiovascular dysfunction. Several pathophysiological mechanisms have been proposed linking hypoglycemia to increased cardiovascular risk, including hemodynamic changes, myocardial ischemia, abnormal cardiac repolarization, cardiac arrhythmias, prothrombotic and proinflammatory effects, and induction of oxidative stress. Hypoglycemia-induced changes can promote the development of endothelial dysfunction, which is an early marker of atherosclerosis. Although data from clinical trials and real-world studies suggest an association between hypoglycemia and cardiovascular events in patients with diabetes, it remains uncertain whether this association is causal. New therapeutic agents for patients with T2D do not cause hypoglycemia and have cardioprotective benefits, whereas increasing the use of new technologies, such as continuous glucose monitoring devices and insulin pumps, has the potential to reduce hypoglycemia and its adverse cardiovascular outcomes in patients with T1D.

Sustained heart rate-corrected QT prolongation during recovery from hypoglycaemia in people with type 1 diabetes, independently of recovery to hyperglycaemia or euglycaemia

AIM

To investigate changes in cardiac repolarization abnormalities (heart rate-corrected QT [QT_c ] [primary endpoint], T-wave abnormalities) and heart-rate variability measures in people with type 1 diabetes during insulin-induced hypoglycaemia followed by recovery hyperglycaemia versus euglycaemia.

METHODS

In a randomized crossover study, 24 individuals with type 1 diabetes underwent two experimental clamps with three steady-state phases during electrocardiographic monitoring: (1) a 45-minute euglycaemic phase (5-8 mmol/L), (2) a 60-minute insulin-induced hypoglycaemic phase (2.5 mmol/L), and (3) 60-minute recovery in either hyperglycaemia (20 mmol/L) or euglycaemia (5-8 mmol/L).

RESULTS

All measured markers of arrhythmic risk indicated increased risk during hypoglycaemia. These findings were accompanied by a decrease in vagal tone during both hyperglycaemia and euglycaemia clamps. Compared with baseline, the QT_c interval increased during hypoglycaemia, and 63% of the participants exhibited a peak QT_c of more than 500 ms. The prolonged QT_c interval was sustained during both recovery phases with no difference between recovery hyperglycaemia versus euglycaemia. During recovery, no change from baseline was observed in heart-rate variability measures.

CONCLUSIONS

In people with type 1 diabetes, insulin-induced hypoglycaemia prolongs cardiac repolarization, which is sustained during a 60-minute recovery period independently of recovery to hyperglycaemia or euglycaemia. Thus, vulnerability to serious cardiac arrhythmias and sudden cardiac death may extend beyond a hypoglycaemic event, regardless of hyperglycaemic or euglycaemic recovery.

Exercise-related hypoglycaemia induces QTc-interval prolongation in individuals with type 1 diabetes

AIMS

To investigate changes in cardiac repolarisation during exercise-related hypoglycaemia compared to hypoglycaemia induced at rest in people with type 1 diabetes.

MATERIAL AND METHODS

In a randomised crossover study, 15 men with type 1 diabetes underwent two separate hyperinsulinaemic euglycaemic-hypoglycaemic clamp experiments during Holter-ECG monitoring. One experiment included a bout of moderate-intensity cycling exercise (60 min) along with declining plasma glucose (PG; Clamp-exercise). In the other experiment, hypoglycaemia was induced with the participants at rest (Clamp-rest). We studied QTc interval, T-peak to T-end (Tpe) interval and hormonal responses during three steady-state phases: (i) baseline (PG 4.0-8.0 mmol/L); (ii) hypoglycaemic phase (PG <3.0 mmol/L); and (iii) recovery phase (PG 4.0-8.0 mmol/L).

RESULTS

Both QTc interval and Tpe interval increased significantly from baseline during the hypoglycaemic phase but with no significant difference between test days. These changes were accompanied by an increase in plasma adrenaline and a decrease in plasma potassium on both days. During the recovery phase, ΔQTc interval was longer during Clamp-rest compared to Clamp-exercise, whereas ΔTpe interval remained similar on the two test days.

CONCLUSIONS

We found that both exercise-related hypoglycaemia and hypoglycaemia induced at rest can cause QTc-interval prolongation and Tpe-interval prolongation in people with type 1 diabetes. Thus, both scenarios may increase susceptibility to ventricular arrhythmias.

Detecting hypoglycemia-induced electrocardiogram changes in a rodent model of type 1 diabetes using shape-based clustering

Sudden death related to hypoglycemia is thought to be due to cardiac arrhythmias. A clearer understanding of the cardiac changes associated with hypoglycemia is needed to reduce mortality. The objective of this work was to identify distinct patterns of electrocardiogram heartbeat changes that correlated with glycemic level, diabetes status, and mortality using a rodent model. Electrocardiogram and glucose measurements were collected from 54 diabetic and 37 non-diabetic rats undergoing insulin-induced hypoglycemic clamps. Shape-based unsupervised clustering was performed to identify distinct clusters of electrocardiogram heartbeats, and clustering performance was assessed using internal evaluation metrics. Clusters were evaluated by experimental conditions of diabetes status, glycemic level, and death status. Overall, shape-based unsupervised clustering identified 10 clusters of ECG heartbeats across multiple internal evaluation metrics. Several clusters demonstrating normal ECG morphology were specific to hypoglycemia conditions (Clusters 3, 5, and 8), non-diabetic rats (Cluster 4), or were generalized among all experimental conditions (Cluster 1). In contrast, clusters demonstrating QT prolongation alone or a combination of QT, PR, and QRS prolongation were specific to severe hypoglycemia experimental conditions and were stratified heartbeats by non-diabetic (Clusters 2 and 6) or diabetic status (Clusters 9 and 10). One cluster demonstrated an arrthymogenic waveform with premature ventricular contractions and was specific to heartbeats from severe hypoglycemia conditions (Cluster 7). Overall, this study provides the first data-driven characterization of ECG heartbeats in a rodent model of diabetes during hypoglycemia.

Utilization of Personalized Machine-Learning to Screen for Dysglycemia from Ambulatory ECG, toward Noninvasive Blood Glucose Monitoring

Blood glucose (BG) monitoring is important for critically ill patients, as poor sugar control has been associated with increased mortality in hospitalized patients. However, constant BG monitoring can be resource-intensive and pose a healthcare burden in clinical practice. In this study, we aimed to develop a personalized machine-learning model to predict dysglycemia from electrocardiogram (ECG) data. We used the Medical Information Mart for Intensive Care III database as our source of data and obtained more than 20 ECG records from each included patient during a single hospital admission. We focused on lead II recordings, along with corresponding blood sugar data. We processed the data and used ECG features from each heartbeat as inputs to develop a one-class support vector machine algorithm to predict dysglycemia. The model was able to predict dysglycemia using a single heartbeat with an AUC of 0.92 ± 0.09, a sensitivity of 0.92 ± 0.10, and specificity of 0.84 ± 0.04. After applying 10 s majority voting, the AUC of the model's dysglycemia prediction increased to 0.97 ± 0.06. This study showed that a personalized machine-learning algorithm can accurately detect dysglycemia from a single-lead ECG.

Vitamin E treatment in insulin-deficient diabetic rats reduces cardiac arrhythmias and mortality during severe hypoglycemia

In people with type 1 diabetes, hypoglycemia can induce cardiac arrhythmias. In rodent experiments, severe hypoglycemia can induce fatal cardiac arrhythmias, especially so in diabetic models. Increased oxidative stress associated with insulin-deficient diabetes was hypothesized to increase susceptibility to severe hypoglycemia-induced fatal cardiac arrhythmias. To test this hypothesis, Sprague-Dawley rats were made insulin deficient with streptozotocin and randomized into two groups: 1) control (n = 22) or 2) vitamin E treated (four doses of α-tocopherol, 400 mg/kg, n = 20). Following 1 week of treatment, rats were either tested for cardiac oxidative stress or underwent a hyperinsulinemic-severe hypoglycemic (10-15 mg/dL) clamp with electrocardiogram recording. As compared with controls, vitamin E-treated rats had threefold less cardiac oxidative stress, sixfold less mortality due to severe hypoglycemia, and sevenfold less incidence of heart block. In summary, vitamin E treatment and the associated reduction of cardiac oxidative stress in diabetic rats reduced severe hypoglycemia-induced fatal cardiac arrhythmias. These results indicate that in the setting of diabetes, pharmacological treatments that reduce oxidative stress may be an effective strategy to reduce the risk of severe hypoglycemia-induced fatal cardiac arrhythmias.NEW & NOTEWORTHY For people with type 1 diabetes, severe hypoglycemia can be fatal. We show in our animal model that insulin-deficient diabetic rats have fatal cardiac arrhythmias during severe hypoglycemia that are associated with increased cardiac oxidative stress. Importantly, treatment with vitamin E, to reduce oxidative stress, decreased fatal cardiac arrhythmias during severe hypoglycemia.

High incidence of undetected low sensor glucose events among elderly patients with type 2 diabetes more than a decade on after the ACCORD study

OBJECTIVE

Hypoglycaemia leads to significant morbidity and impacts negatively on quality-of-life, especially in elderly people with increased frailty. The aims of this study were to determine the prevalence of low interstitial fluid glucose (IFG) in patients with tightly controlled type 2 diabetes (T2D), and to evaluate whether there were differences in burden of low IFG between sulphonylurea and insulin treated groups.

METHODS

A Freestyle Libre-Pro sensor was used for sampling of the IFG continuously. Patients were blinded to the IFG levels. The sensor was returned to the investigators after a 2-week period and the data were downloaded for analysis.

RESULTS

There was a total of 69 patients (median age 72 years (IQR = 69-74)) - 40 were sulfonylurea-treated and 29 insulin-treated. In total, 781 low sensor glucose events (<4.0 mmol/L) were detected, of which 254 were very low sensor glucose events (<2.8 mmol/L). Twenty-six out of 29 insulin-treated (89.6%) and 36 out of 40 sulphonylurea-treated patients (90%) contributed to the 781 events of low sensor glucose. Twenty out of 29 insulin-treated (69%) and 26 out of 40 sulphonylurea-treated patients (65.0%) contributed to the 254 very low sensor glucose events. Only 9% of all events were identified by patients. Nocturnal events represented 55.8% of low sensor glucose events and 61.0% of very low sensor glucose events. At a cut-off of <2.8 mmol/L, it was found that the insulin group had a significantly greater number of such events as compared to the sulfonylurea group.

CONCLUSIONS

This study demonstrates that elderly patients with tightly-controlled T2D have a significant number of low sensor glucose events which go by undetected.

Stress, hypoglycemia, and the autonomic nervous system

Stress can be classified as either psychosocial or physiologic. Physiologic stress refers to stresses due to acute illness, trauma, pain, hypoglycemia, and sleep deprivation-much less is known regarding its health consequences. This review focuses on hypoglycemia as a model to further investigate physiological stress. Experimental mild to moderate hypoglycemia is a paradigmatic physiological stress that evokes autonomic, neuroendocrine, and immune responses. Hypoglycemic stress is an ideal model to examine the interactions and consequences of physiological stress on the autonomic nervous system. Acute hypoglycemia has been demonstrated to increase inflammatory markers, prolong QTc, and impair cardiac-vagal baroreflex sensitivity. Some of these consequences may not reverse completely when euglycemia is restored. For example, there is attenuation of the cardiac-vagal baroreflex, attenuation of the vascular sympathetic baroreflex (muscle sympathetic nerve activity response to transient hypotension), and attenuation of the catecholamine response to lower body negative pressure that is present the next day after hypoglycemia has resolved.

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 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.

Autonomic cardiac regulation during spontaneous nocturnal hypoglycemia in children with type 1 diabetes

BACKGROUND

Hypoglycemia is the most common complication in insulin treated diabetes. Though mostly mild, it can be fatal in rare cases: It is hypothesized that hypoglycemia related QTc prolongation contributes to cardiac arrhythmia.

OBJECTIVE

To evaluate influence of nocturnal hypoglycemia on QTc and heart rate variability (HRV) in children with T1D.

METHODS

Children and adolescents with T1D for at least 6 months participated in an observational study using continuous glucose monitoring (CGM) and Holter electrocardiogram for five consecutive nights. Mean QTc was calculated for episodes of nocturnal hypoglycemia (<3.7 mmol/L) and compared to periods of the same duration preceding hypoglycemia. HRV (RMSSD, low and high frequency power LF and HF) was analyzed for different 15 min intervals: before hypoglycemia, onset of hypoglycemia, before/after nadir, end of hypoglycemia and after hypoglycemia.

RESULTS

Mean QTc during hypoglycemia was significantly longer compared to euglycemia (412 ± 15 vs. 405 ± 18 ms, p = 0.005). HRV changed significantly: RMSSD (from 88 ± 57 to 73 ± 43 ms) and HF (from 54 ± 17 to 47 ± 17nu) decreased from before hypoglycemia to after nadir, while heart rate (from 69 ± 9 to 72 ± 12 bpm) and LF (from 44 ± 17 to 52 ± 21 nu) increased (p = 0.04).

CONCLUSION

A QTc lengthening effect of nocturnal hypoglycemia in children with T1D was documented. HRV changes occurred even before detection of nocturnal hypoglycemia by CGM, which may be useful for hypoglycemia prediction.

Glucagon as a Therapeutic Approach to Severe Hypoglycemia: After 100 Years, Is It Still the Antidote of Insulin?

Hypoglycemia represents a dark and tormented side of diabetes mellitus therapy. Patients treated with insulin or drug inducing hypoglycemia, consider hypoglycemia as a harmful element, which leads to their resistance and lack of acceptance of the pathology and relative therapies. Severe hypoglycemia, in itself, is a risk for patients and relatives. The possibility to have novel strategies and scientific knowledge concerning hypoglycemia could represent an enormous benefit. Novel available glucagon formulations, even now, allow clinicians to deal with hypoglycemia differently with respect to past years. Novel scientific evidence leads to advances concerning physiopathological mechanisms that regulated glycemic homeostasis. In this review, we will try to show some of the important aspects of this field.

Acute hypoglycemia and risk of cardiac arrhythmias in insulin-treated type 2 diabetes and controls

OBJECTIVE

Hypoglycemia is associated with an increased risk of cardiovascular disease including cardiac arrhythmias. We investigated the effect of hypoglycemia in the setting of acute glycemic fluctuations on cardiac rhythm and cardiac repolarization in insulin-treated patients with type 2 diabetes compared with matched controls without diabetes.

DESIGN

A non-randomized, mechanistic intervention study.

METHODS

Insulin-treated patients with type 2 diabetes (n = 21, age (mean ± s.d.): 62.8 ± 6.5 years, BMI: 29.0 ± 4.2 kg/m2, HbA1c: 6.8 ± 0.5% (51.0 ± 5.4 mmol/mol)) and matched controls (n = 21, age: 62.2 ± 8.3 years, BMI 29.2 ± 3.5 kg/m2, HbA1c: 5.3 ± 0.3% (34.3 ± 3.3 mmol/mol)) underwent a sequential hyperglycemic and hypoglycemic clamp with three steady-states of plasma glucose: (i) fasting plasma glucose, (ii) hyperglycemia (fasting plasma glucose +10 mmol/L) and (iii) hyperinsulinemic hypoglycemia (plasma glucose < 3.0 mmol/L). Participants underwent continuous ECG monitoring and blood samples for counterregulatory hormones and plasma potassium were obtained.

RESULTS

Both groups experienced progressively increasing heart rate corrected QT (Fridericia's formula) interval prolongations during hypoglycemia ((∆mean (95% CI): 31 ms (16, 45) and 39 ms (24, 53) in the group of patients with type 2 diabetes and controls, respectively) with similar increases from baseline at the end of the hypoglycemic phase (P = 0.43). The incidence of ventricular premature beats increased significantly in both groups during hypoglycemia (P = 0.033 and P < 0.0001, respectively). One patient with type 2 diabetes developed atrial fibrillation during recovery from hypoglycemia.

CONCLUSIONS

In insulin-treated patients with type 2 diabetes and controls without diabetes, hypoglycemia causes clinically significant and similar increases in cardiac repolarization that might increase vulnerability for serious cardiac arrhythmias and sudden cardiac death.

Less is More: Deprescribing Medications in Older Adults with Kidney Disease: A Review

Due to age and impaired kidney function, older adults with kidney disease are at increased risk of medication-related problems and related hospitalizations. One proa ctive approach to minimize this risk is deprescribing. Deprescribing refers to the systematic process of reducing or stopping a medication. Aside from preventing harm, deprescribing can potentially optimize patients' quality of life by aligning medications with their goals of care. For some patients, deprescribing could involve less aggressive management of their diabetes and/or hypertension. In other instances, deprescribing targets may include potentially inappropriate medications that carry greater risk of harm than benefit in older adults, medications that have questionable efficacy, including medications that have varying efficacy by degree of kidney function, and that increase medication regimen complexity. We include a guide for clinicians to utilize in deprescribing, the List, Evaluate, Shared Decision-Making, Support (LESS) framework. The LESS framework provides key considerations at each step of the deprescribing process that can be tailored for the medications and context of individu al patients. Patient characteristics or clinical events that warrant consideration of deprescribing include limited life expectancy, cognitive impairment, and health status changes, such as dialysis initiation or recent hospitalization. We acknowledge patient-, clinician-, and system-level challenges to the depre scribing process. These include patient hesitancy and challenges to discussing goals of care, clinician time constraints and a lack of evidence-based guidelines, and system-level challenges of interoperable electronic health records and limited incentives for deprescribing. However, novel evidence-based tools designed to facilitate deprescribing and future evidence on effectiveness of deprescribing could help mitigate these barriers. This review provides foundational knowledge on deprescribing as an emerging component of clinical practice and research within nephrology.

Age-dependent transition from islet insulin hypersecretion to hyposecretion in mice with the long QT-syndrome loss-of-function mutation Kcnq1-A340V

Loss-of-function (LoF) mutations in KCNQ1, encoding the voltage-gated K⁺ channel K_v7.1, lead to long QT syndrome 1 (LQT1). LQT1 patients also present with post-prandial hyperinsulinemia and hypoglycaemia. In contrast, KCNQ1 polymorphisms are associated with diabetes, and LQTS patients have a higher prevalence of diabetes. We developed a mouse model with a LoF Kcnq1 mutation using CRISPR-Cas9 and hypothesized that this mouse model would display QT prolongation, increased glucose-stimulated insulin secretion and allow for interrogation of K_v7.1 function in islets. Mice were characterized by electrocardiography and oral glucose tolerance tests. Ex vivo, islet glucose-induced insulin release was measured, and beta-cell area quantified by immunohistochemistry. Homozygous mice had QT prolongation. Ex vivo, glucose-stimulated insulin release was increased in islets from homozygous mice at 12–14 weeks, while beta-cell area was reduced. Non-fasting blood glucose levels were decreased at this age. In follow-up studies 8–10 weeks later, beta-cell area was similar in all groups, while glucose-stimulated insulin secretion was now reduced in islets from hetero- and homozygous mice. Non-fasting blood glucose levels had normalized. These data suggest that K_v7.1 dysfunction is involved in a transition from hyper- to hyposecretion of insulin, potentially explaining the association with both hypoglycemia and hyperglycemia in LQT1 patients.

Significant abnormal glycemic variability increased the risk for arrhythmias in elderly type 2 diabetic patients

BACKGROUND

Little is known about whether the influence of glycemic variability on arrhythmia is related to age in type 2 diabetes mellitus (T2DM). Therefore, we aimed to compare the association between glycemic variability and arrhythmia in middle-aged and elderly T2DM patients.

METHODS

A total of 107 patients were divided into two groups: elderly diabetes mellitus group (EDM, n = 73) and middle-aged diabetes mellitus group (MDM, n = 34). The main clinical data, continuous glucose monitoring (CGM) and dynamic ECG reports were collected. The parameters including standard deviation of blood glucose (SDBG), largest amplitude of glycemic excursions (LAGE), mean amplitude of glycemic excursions (MAGE), absolute means of daily differences (MODD), time in range (TIR), time below range (TBR), time above range (TAR), coefficient of variation (CV) were tested for glycemic variability evaluation.

RESULTS

In terms of blood glucose fluctuations, MAGE (5.77 ± 2.16 mmol/L vs 4.63 ± 1.89 mmol/L, P = 0.026), SDBG (2.39 ± 1.00 mmol/L vs 2.00 ± 0.82 mmol/L, P = 0.048), LAGE (9.53 ± 3.37 mmol/L vs 7.84 ± 2.64 mmol/L, P = 0.011) was significantly higher in EDM group than those of MDM group. The incidences of atrial premature beat, couplets of atrial premature beat, atrial tachycardia and ventricular premature beat were significantly higher in EDM group compared with the MDM group (all P < 0.05). Among patients with hypoglycemia events, the incidences of atrial premature beat, couplets of atrial premature beat, atrial tachycardia and ventricular premature beat (all P < 0.05) were significantly higher in the EDM group than those in the MDM group. In EDM group, TIR was negatively correlated with atrial tachycardia in the MAGE1 layer and with atrial tachycardia and ventricular premature beat in the MAGE2 layer, TBR was significantly positively correlated with atrial tachycardia in the MAGE2 layer (all P < 0.05). In MDM group, TAR was positively correlated with ventricular premature beat and atrial tachycardia in the MAGE2 layer (all P < 0.05).

CONCLUSIONS

The study demonstrated the elderly patients had greater glycemic variability and were more prone to arrhythmias. Therefore, active control of blood glucose fluctuation in elderly patients will help to reduce the risk of severe arrhythmia.

The Prophylactic Effects of Metoprolol, Diltiazem, and Pilocarpine on Hypoglycemia-Induced Prolongation of QT Interval

Background Insulin-induced hypoglycemia has been demonstrated to prolong the corrected QT (QTc) interval. Prolongation of the QTc interval, especially in diabetic patients using insulin, can cause fatal ventricular arrhythmias. The aim of this study was to evaluate the effects of metoprolol, diltiazem, and pilocarpine on hypoglycemia-induced QTc prolongation. Methods Thirty male rats were randomly distributed into the following five groups: Group 1 (1 mL/kg saline, n=6), Group 2 (40 U/kg crystalline insulin + saline, n=6), Group 3 (40 U/kg crystalline insulin + 1 mg/kg metoprolol, n=6), Group 4 (40 U/kg crystalline insulin + 0.8 mg/kg pilocarpine, n=6), and Group 5 (40 U/kg crystalline insulin + 2 mg/kg diltiazem, n=6). Three hours after insulin injection, the blood glucose level was measured in all groups. Blood glucose <40 mg/dl was defined as hypoglycemia. Electrocardiograms (ECG) were taken in lead I (DI), and QTc was calculated by using Bazett's formula. Results Group 2 (insulin + saline) showed that it had a significantly prolonged QTc interval as compared to the control group (p<0.0001). However, treatments of the rats with metoprolol, pilocarpine, and diltiazem significantly prevented prolongation of the QTc interval as compared to the insulin + saline group (p<0.005, p<0.005, and p<0.01, respectively). Conclusion The findings of the present study demonstrated the efficacy of metoprolol, pilocarpine, and diltiazem in the prevention of hypoglycemia-induced QTc prolongation in male rats.

Hyperinsulinaemic hypoglycaemia in non-anaesthetized Göttingen minipigs induces a counter-regulatory endocrine response and electrocardiographic changes

The potentially fatal cardiovascular effects of hypoglycaemia are not well understood and large animal models of the counter-regulatory responses and cardiovascular consequences of insulin-induced hypoglycaemia are needed to understand the mechanisms in humans. The aim of this study was to develop a human-like minipig model of hypoglycaemia including healthy and diabetic pigs to investigate endocrine, electrocardiographic and platelet effects. Hypoglycaemia was induced using a hyperinsulinaemic, hypoglycaemic clamp and an insulin bolus protocol. Plasma glucose, glucagon, C-peptide, insulin, epinephrine and platelet aggregation responses were measured before, during and after hypoglycaemia. Continuous electrocardiographic recordings were obtained. Hypoglycaemia at a plasma glucose concentration of 0.8–1.0 mM in the clamp induced 25-fold increase in epinephrine and sixfold and threefold increase in glucagon for healthy and diabetic pigs, respectively. The hypoglycaemic clamp induced QTc-interval prolongation and increase in cardiac arrhythmias. In the bolus approach, the non-diabetic group reached plasma glucose target of 1.5 mM and QTc-interval was prolonged after insulin injection, but before glucose nadir. The diabetic group did not reach hypoglycaemic target, but still demonstrated QTc-interval prolongation. These results demonstrate effects of hyperinsulinaemic hypoglycaemia closely resembling human physiology, indicating the minipig as a translational animal model of counter-regulatory endocrine and myocardial effects of hypoglycaemia.

Glucose Homeostasis, Hypoglycemia, and the Burnt-Out Diabetes Phenomenon in Kidney Disease

Chronic kidney disease (CKD) is among the most prevalent and dire complications of diabetes mellitus in adults across the world. Diabetes substantially contributes to the burden of kidney disease, such that one third to one half of CKD in the United States and many other countries is attributable to diabetic kidney disease (DKD). As DKD progresses to end-stage renal disease (ESRD), patients are at heightened risk for atypical glycemic complications, including the development of burnt-out diabetes, manifested by hypoglycemic bouts and poor outcomes. Furthermore, even in the absence of diabetes, hypoglycemia is a frequent occurrence in CKD patients that may contribute to their high burden of cardiovascular disease and death. Extrapolation of data from clinical trials in high-cardiovascular-risk populations and observational studies in patients with non-dialysis-dependent (NDD) CKD and ESRD suggest that moderate glycemic targets defined by glycated hemoglobin levels of 6% to 8% and glucose levels of 100 to 150 mg/dL are associated with better survival in DKD patients. However, given the imprecision of glycated hemoglobin levels in kidney disease, further research is needed to determine the optimal glycemic metric and target in diabetic NDD-CKD and ESRD patients. Given their exceedingly high cardiovascular morbidity and mortality, there is a compelling need for further investigation of how to optimally manage dysglycemia in the NDD-CKD and ESRD populations.

Management of diabetes and hyperglycaemia in the hospital

Hyperglycaemia in people with and without diabetes admitted to the hospital is associated with a substantial increase in morbidity, mortality, and health-care costs. Professional societies have recommended insulin therapy as the cornerstone of inpatient pharmacological management. Intravenous insulin therapy is the treatment of choice in the critical care setting. In non-intensive care settings, several insulin protocols have been proposed to manage patients with hyperglycaemia; however, meta-analyses comparing different treatment regimens have not clearly endorsed the benefits of any particular strategy. Clinical guidelines recommend stopping oral antidiabetes drugs during hospitalisation; however, in some countries continuation of oral antidiabetes drugs is commonplace in some patients with type 2 diabetes admitted to hospital, and findings from clinical trials have suggested that non-insulin drugs, alone or in combination with basal insulin, can be used to achieve appropriate glycaemic control in selected populations. Advances in diabetes technology are revolutionising day-to-day diabetes care and work is ongoing to implement these technologies (ie, continuous glucose monitoring, automated insulin delivery) for inpatient care. Additionally, transformations in care have occurred during the COVID-19 pandemic, including the use of remote inpatient diabetes management-research is needed to assess the effects of such adaptations.

In vivo cardiopulmonary impact of skeletal M3Dq DREADD expression: a pilot study

The muscarinic M₃ receptor (M₃R) is implicated in cardiopulmonary control and many other peripheral physiologic functions. Previous observations report mortality in mice expressing a Gq-linked designer G-protein coupled receptor (Dq) selectively in striated muscle, while M₃Dq DREADD (Designer Receptor Exclusively Activated by Designer Drug), selectively expressed in skeletal muscle (SKM) impacts glucose metabolism. We investigated whether activation of SKM M₃Dq impacts cardiopulmonary function. Heart rate (HR), body temperature (Tb) and locomotor activity (ACT) were measured in 4 conscious, chronically instrumented M₃Dq DREADD mice and 4 wildtype controls. Circadian values of HR, BT and ACT were not different between genotypes (p > 0.05). Activation of the M₃Dq DREADD by clozapine N-oxide (CNO; 0.1 mg/kg) resulted in: a significant drop in heart rate, 2 h after injection, compared with a time-matched baseline control period from the same animals (460 ± 28 vs. 532 ± 6, p < 0.05), significantly lower ACT compared to the baseline control (p < 0.05) and reduced pulmonary minute ventilation compared to pre-CNO control (p < 0.05). M₃Dq DREADD activation did not cause bronchoconstriction (separate protocol), however, there was a concomitant reduction in HR, Tb and ventilation, accompanied by cardiac arrhythmias. We speculate that reductions in Tb, HR and ventilation reflect a mechanistic link between SKM Gq signaling and the metabolic responses associated with the initiation of torpor. Supported by the Canadian Institutes of Health Research (CIHR MOP-81211).

Risk of severe hypoglycaemia and its impact in type 2 diabetes in DEVOTE

AIMS

To undertake a post-hoc analysis, utilizing a hypoglycaemia risk score based on DEVOTE trial data, to investigate if a high risk of severe hypoglycaemia was associated with an increased risk of cardiovascular events, and whether reduced rates of severe hypoglycaemia in patients identified as having the highest risk affected the risk of cardiovascular outcomes.

MATERIALS AND METHODS

The DEVOTE population was divided into quartiles according to patients' individual hypoglycaemia risk scores. For each quartile, the observed incidence and rate of severe hypoglycaemia, major adverse cardiovascular event (MACE) and all-cause mortality were determined to investigate whether those with the highest risk of hypoglycaemia were also at the greatest risk of MACE and all-cause mortality. In addition, treatment differences within each risk quartile [insulin degludec (degludec) vs. insulin glargine 100 units/mL (glargine U100)] in terms of severe hypoglycaemia, MACE and all-cause mortality were investigated.

RESULTS

Patients with the highest risk scores had the highest rates of severe hypoglycaemia, MACE and all-cause mortality. Treatment ratios between degludec and glargine U100 in the highest risk quartile were 95% confidence interval (CI) 0.56 (0.39; 0.80) (severe hypoglycaemia), 95% CI 0.76 (0.58; 0.99) (MACE) and 95% CI 0.77 (0.55; 1.07) (all-cause mortality).

CONCLUSIONS

The risk score demonstrated that a high risk of severe hypoglycaemia was associated with a high incidence of MACE and all-cause mortality and that, in this high-risk group, those treated with degludec had a lower incidence of MACE. These observations support the hypothesis that hypoglycaemia is a risk factor for cardiovascular events.

Cardiovascular disease in type 1 diabetes: A review of epidemiological data and underlying mechanisms

Cardiovascular disease (CVD) is highly prevalent in patients with type 1 diabetes (T1D) and a major cause of mortality. CVD arises earlier in life in T1D patients and is responsible for a significant reduction of at least 11 years' life expectancy. Also, the incidence of CVD is much more pronounced in patients with T1D onset at an earlier age. However, the factors responsible for increased atherosclerosis and CVD in T1D are not yet totally clarified. In addition to the usual cardiovascular (CV) risk factors, chronic hyperglycaemia plays an important role by promoting oxidative stress, vascular inflammation, monocyte adhesion, arterial wall thickening and endothelial dysfunction. Diabetic nephropathy and cardiac autonomic neuropathy are also associated with increased CVD in T1D. In fact, the CVD risk remains significantly increased even in well-controlled T1D patients who have no additional CV risk factors, indicating that other potential factors are likely to be involved. Hypoglycemia and glucose variability could enhance CV disease by promoting oxidative stress, vascular inflammation and endothelial dysfunction. Furthermore, even well-controlled T1D patients show significant qualitative and functional abnormalities of lipoproteins that are likely to be implicated in the development of atherosclerosis and premature CVD. In addition, recent data suggest that a dysfunctional immune system, which is typical of autoimmune T1D, might also promote CVD possibly through inflammatory pathways. Moreover, overweight and obese T1D patients can manifest additional CV risk through pathophysiological mechanisms resembling those observed in type 2 diabetes (T2D).

Experimental Models of Impaired Hypoglycaemia-Associated Counter-Regulation

Impaired awareness of hypoglycaemia (IAH) affects around a quarter of patients with diabetes who receive insulin treatment. This condition is characterised by a progressive reduction in symptomatic and behavioural responses to hypoglycaemia, increasing risk of deeper drops in blood glucose, unconsciousness, and collapse. Thus, patients with IAH experience severe hypoglycaemic episodes more frequently, resulting in significant morbidity and mortality. IAH is thought to develop as a consequence of whole-body adaptations to repeated insulin-induced hypoglycaemia (RH), with widespread deficits in the hypoglycaemia counter-regulatory response (CRR). Despite this important insight, the precise pathophysiology by which RH leads to an attenuated CRR is unknown. Studies into the underlying mechanisms of IAH have employed a variety of protocols in humans and experimental species. The use of animal models has many investigational benefits, including the unprecedented increase in the availability of transgenic strains. However, modelling impaired hypoglycaemia-associated counter-regulation remains challenging and appropriate interpretation of findings across species and protocols even more so. Here, we review the experimental modelling of IAH and impaired hypoglycaemia-associated counter-regulation, with a focus on understanding species-specific variation in glucose homeostasis. This review will aid investigators in interpreting outputs from different studies in IAH and aid progress in the field.

Increased Plasma Levels of Adenylate Cyclase 8 and cAMP Are Associated with Obesity and Type 2 Diabetes: Results from a Cross-Sectional Study

Adenylate cyclases (ADCYs) catalyze the conversion of ATP to cAMP, an important co-factor in energy homeostasis. Giving ADCYs role in obesity, diabetes and inflammation, we questioned whether calcium-stimulated ADCY isoforms may be variably detectable in human plasma. We report the results of a cross-sectional study assessing circulating levels of functional ADCY1, -3 and -8 in patients with T2D vs. non-diabetic (ND) controls in association with obesity. ADCY1 levels exhibited no significant change between ND and T2D groups. ADCY3 levels were lower in obese individuals, albeit not statistically significantly. In contrast, ADCY8 plasma levels were significantly higher in obese and T2D patients compared to controls (p = 0.001) and patients with T2D only (p = 0.039). ADCY8 levels correlated positively with body mass index and Hb1Ac levels. Parallel to the increased ADCY8 levels, significantly higher cAMP levels were observed in patients with T2D compared with ND controls, and further elevated in obese individuals, irrespective of T2D status. Additionally, cAMP levels positively correlated with fasting plasma glucose levels. In conclusion, the current cross-sectional study demonstrated elevated levels of circulating plasma ADCY8 and cAMP in obesity and T2D.

ACTH Infusion Impairs Baroreflex Sensitivity-Implications for Cardiovascular Hypoglycemia-Associated Autonomic Failure

CONTEXT

Hypoglycemia attenuates cardiovascular homeostatic autonomic control. This attenuation, known as the cardiovascular component of hypoglycemia-associated autonomic failure (HAAF), is characterized most notably by decreased baroreflex sensitivity (BRS) that begins during hypoglycemia and persists until at least the next day, despite return to euglycemia. Understanding the mechanisms underlying this reduction in BRS is important because BRS attenuation is associated with increased morbidity and mortality.

OBJECTIVE

The objective of this work is to investigate the role of the adrenocorticotropin (ACTH)-adrenal axis in decreasing BRS. We tested the hypothesis that infusion of ACTH 1-24 (cosyntropin), as compared to placebo, would acutely suppress BRS, and that this decrease in BRS would be present the next day.

DESIGN

A double-blind, placebo-controlled, random-order, cross-over study was conducted.

SETTING

This study took place in a clinical research center.

PARTICIPANTS

Participants included healthy men and women.

INTERVENTIONS

Interventions included an intravenous infusion of cosyntropin (70 μg/hour for 2.5 hours in the morning and again in the early afternoon) vs normal saline placebo.

MAIN OUTCOME MEASURES

Outcome measures included BRS during and 16 hours after cosyntropin vs placebo infusions.

RESULTS

Cosyntropin infusion attenuated BRS (mm Hg/ms) as compared to placebo (baseline 17.8 ± 1.38 vs 17.0 ± 2.07; during 14.4 ± 1.43 vs 17.3 ± 1.65; and next day 14.8 ± 1.42 vs 18.9 ± 2.04; P < .05, time by treatment, analysis of variance). BRS was decreased during the final 30 minutes of the morning cosyntropin infusion as compared to baseline (P < .01) and remained suppressed the next day (16 hours after afternoon infusion) (P < .025). Placebo infusion did not significantly change BRS. Corrected QT interval was not affected.

CONCLUSIONS

ACTH attenuates BRS, raising the possibility that hypoglycemia-induced increases in ACTH may contribute to the cardiovascular component of HAAF.

Hypoglycaemia and cardiac arrhythmias in diabetes

Hypoglycaemia remains an inevitable risk in insulin-treated type 1 diabetes and type 2 diabetes and has been associated with multiple adverse outcomes. Whether hypoglycaemia is a cause of fatal cardiac arrhythmias in diabetes, or merely a marker of vulnerability, is still unknown. Since a pivotal report in 1991, hypoglycaemia has been suspected to induce cardiac arrhythmias in patients with type 1 diabetes, the so-called 'dead-in-bed syndrome'. This suspicion has subsequently been supported by the coexistence of an increased mortality and a three-fold increase in severe hypoglycaemia in patients with type 2 diabetes receiving intensive glucose-lowering treatment in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Studies have investigated the association between hypoglycaemia-induced cardiac arrhythmias. In a rat-model, severe hypoglycaemia resulted in a specific pattern of cardiac arrhythmias including QT-prolongation, ventricular tachycardia, second- and third-degree AV block and ultimately cardiorespiratory arrest. In clinical studies of experimentally induced hypoglycaemia, QTc-prolongation, a risk factor of ventricular arrhythmias, is an almost consistent finding. The extent of QT-prolongation seems to be modified by several factors, including antecedent hypoglycaemia, diabetes duration and cardiac autonomic neuropathy. Observational studies indicate diurnal differences in the pattern of electrocardiographic alterations during hypoglycaemia with larger QTc-prolongations during daytime, whereas the risk of bradyarrhythmias may be increased during sleep. Daytime periods of hypoglycaemia are characterized by shorter duration, increased awareness and a larger increase in catecholamines. The counterregulatory response is reduced during nightly episodes of hypoglycaemia, resulting in prolonged periods of hypoglycaemia with multiple nadirs. An initial sympathetic activity at plasma glucose nadir is replaced by increased vagal activity, which results in bradycardia. Here, we provide an overview of the existing literature exploring potential mechanisms for hypoglycaemia-induced cardiac arrhythmias and studies linking hypoglycaemia to cardiac arrhythmias in patients with diabetes.

Impact of low fasting plasma glucose on mortality in the general population

BACKGROUND

While the association between hypoglycaemia and poor outcomes in diabetes is well established, it is unclear whether such an association is generalizable to those without diabetes.

METHODS

A total of 8497 participants free of cardiovascular disease and diabetes from the Third National Health and Nutrition Examination Survey were included. We examined the relationship between baseline low (<80 mg/dL) and high (⩾126 mg/dL) fasting plasma glucose compared to normal levels (80-99 mg/dL).

RESULTS

Over a median follow-up of 14 years, 2101 deaths occurred, of which 570 were due to cardiovascular disease. In a model adjusted for sociodemographic and cardiovascular disease risk factors, individuals with low fasting plasma glucose were at increased risk of cardiovascular disease and all-cause mortality [hazard ratio = 1.79 (95% confidence interval = 1.04-3.08) and hazard ratio = 1.35 (95% confidence interval = 1.02-1.78), respectively], compared to those with normal fasting plasma glucose. These associations were stronger among men than women for both cardiovascular disease mortality and all-cause mortality.

CONCLUSION

Low fasting plasma glucose in individuals without diabetes is a risk factor for cardiovascular disease and all-cause mortality, especially in men.

Redefining Hypoglycemia in Clinical Trials: Validation of Definitions Recently Adopted by the American Diabetes Association/European Association for the Study of Diabetes

OBJECTIVE

To determine if the International Hypoglycaemia Study Group (IHSG) level 2 low glucose definition can identify clinically relevant hypoglycemia in clinical trials and offer value as an end point for future trials.

RESEARCH DESIGN AND METHODS

A post hoc analysis was performed of the SWITCH (SWITCH 1: n = 501, type 1 diabetes; SWITCH 2: n = 721, type 2 diabetes) and DEVOTE (n = 7,637, type 2 diabetes) trials utilizing the IHSG low glucose definitions. Patients in all trials were randomized to either insulin degludec or insulin glargine 100 units/mL. In the main analysis, the following definitions were compared: 1) American Diabetes Association (ADA) 2005 (plasma glucose [PG] confirmed ≤3.9 mmol/L with symptoms); and 2) IHSG level 2 (PG confirmed <3.0 mmol/L, independent of symptoms).

RESULTS

In SWITCH 2, the estimated rate ratios of hypoglycemic events indicated increasing differences between treatments with decreasing PG levels until 3.0 mmol/L, following which no additional treatment differences were observed. Similar results were observed for the SWITCH 1 trial. In SWITCH 2, the IHSG level 2 definition produced a rate ratio that was lower than the ADA 2005 definition.

CONCLUSIONS

The IHSG level 2 definition was validated in a series of clinical trials, demonstrating its ability to discriminate between basal insulins. This definition is therefore recommended to be uniformly adopted by regulatory bodies and used in future clinical trials.

Clinical Outcomes in Patients With Isolated or Combined Diabetic Ketoacidosis and Hyperosmolar Hyperglycemic State: A Retrospective, Hospital-Based Cohort Study

OBJECTIVE

Many patients with hyperglycemic crises present with combined features of diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS). The implications of concomitant acidosis and hyperosmolality are not well known. We investigated hospital outcomes in patients with isolated or combined hyperglycemic crises.

RESEARCH DESIGN AND METHODS

We analyzed admissions data listing DKA or HHS at two academic hospitals. We determined 1) the frequency distributions of HHS, DKA, and combined DKA-HHS (DKA criteria plus elevated effective osmolality); 2) the relationship of markers of severity of illness and clinical comorbidities with 30-day all-cause mortality; and 3) the relationship of hospital complications associated with insulin therapy (hypoglycemia and hypokalemia) with mortality.

RESULTS

There were 1,211 patients who had a first admission with confirmed hyperglycemic crises criteria, 465 (38%) who had isolated DKA, 421 (35%) who had isolated HHS, and 325 (27%) who had combined features of DKA-HHS. After adjustment for age, sex, BMI, race, and Charlson Comorbidity Index score, subjects with combined DKA-HHS had higher in-hospital mortality compared with subjects with isolated hyperglycemic crises (adjusted odds ratio [aOR] 2.7; 95% CI 1.4, 4.9; P = 0.0019). In all groups, hypoglycemia (<40 mg/dL) during treatment was associated with a 4.8-fold increase in mortality (aOR 4.8; 95% CI 1.4, 16.8). Hypokalemia ≤3.5 mEq/L was frequent (55%). Severe hypokalemia (≤2.5 mEq/L) was associated with increased inpatient mortality (aOR 4.9; 95% CI 1.3, 18.8; P = 0.02).

CONCLUSIONS

Combined DKA-HHS is associated with higher mortality compared with isolated DKA or HHS. Severe hypokalemia and severe hypoglycemia are associated with higher hospital mortality in patients with hyperglycemic crises.

Precision Medicine and Artificial Intelligence: A Pilot Study on Deep Learning for Hypoglycemic Events Detection based on ECG

Tracking the fluctuations in blood glucose levels is important for healthy subjects and crucial diabetic patients. Tight glucose monitoring reduces the risk of hypoglycemia, which can result in a series of complications, especially in diabetic patients, such as confusion, irritability, seizure and can even be fatal in specific conditions. Hypoglycemia affects the electrophysiology of the heart. However, due to strong inter-subject heterogeneity, previous studies based on a cohort of subjects failed to deploy electrocardiogram (ECG)-based hypoglycemic detection systems reliably. The current study used personalised medicine approach and Artificial Intelligence (AI) to automatically detect nocturnal hypoglycemia using a few heartbeats of raw ECG signal recorded with non-invasive, wearable devices, in healthy individuals, monitored 24 hours for 14 consecutive days. Additionally, we present a visualisation method enabling clinicians to visualise which part of the ECG signal (e.g., T-wave, ST-interval) is significantly associated with the hypoglycemic event in each subject, overcoming the intelligibility problem of deep-learning methods. These results advance the feasibility of a real-time, non-invasive hypoglycemia alarming system using short excerpts of ECG signal.

Severe Hypoglycemia-Induced Fatal Cardiac Arrhythmias Are Mediated by the Parasympathetic Nervous System in Rats

The contribution of the sympathetic nervous system (SNS) versus the parasympathetic nervous system (PSNS) in mediating fatal cardiac arrhythmias during insulin-induced severe hypoglycemia is not well understood. Therefore, experimental protocols were performed in nondiabetic Sprague-Dawley rats to test the SNS with 1) adrenal demedullation and 2) chemical sympathectomy, and to test the PSNS with 3) surgical vagotomy, 4) nicotinic receptor (mecamylamine) and muscarinic receptor (AQ-RA 741) blockade, and 5) ex vivo heart perfusions with normal or low glucose, acetylcholine (ACh), and/or mecamylamine. In protocols 1-4, 3-h hyperinsulinemic (0.2 units/kg/min) and hypoglycemic (10-15 mg/dL) clamps were performed. Adrenal demedullation and chemical sympathectomy had no effect on mortality or arrhythmias during severe hypoglycemia compared with controls. Vagotomy led to a 6.9-fold decrease in mortality; reduced first- and second-degree heart block 4.6- and 4-fold, respectively; and prevented third-degree heart block compared with controls. Pharmacological blockade of nicotinic receptors, but not muscarinic receptors, prevented heart block and mortality versus controls. Ex vivo heart perfusions demonstrated that neither low glucose nor ACh alone caused arrhythmias, but their combination induced heart block that could be abrogated by nicotinic receptor blockade. Taken together, ACh activation of nicotinic receptors via the vagus nerve is the primary mediator of severe hypoglycemia-induced fatal cardiac arrhythmias.

Hypoglycemia in diabetes: The dark side of diabetes treatment. A patient-centered review

Hypoglycemia is a frequent occurrence in patients with diabetes who are treated with insulin and insulin secretagogues. Hypoglycemia is the limiting factor that prevents patients from achieving the glycemic control known to reduce the microvascular complications of diabetes. Recurrent episodes of hypoglycemia can lead to impaired awareness of hypoglycemia where the first symptom of a low blood sugar is unconsciousness. The fear of hypoglycemia has a significant effect on the quality of life of patients and their families. In the acute setting, hypoglycemia can kill, and clinical trials have demonstrated that a single episode of severe hypoglycemia increases the risk of subsequent mortality and cardiovascular events. Clinicians must make efforts to recognize and prevent hypoglycemia in order to prevent the adverse events associated with this event. Patient education is central to these efforts. Recent developments in glucose monitoring and drug development have provided more approaches that can be used to reduce the risk of hypoglycemia in patients with diabetes.

Text preprocessing for improving hypoglycemia detection from clinical notes - A case study of patients with diabetes

BACKGROUND AND OBJECTIVE

Hypoglycemia is a common safety event when attempting to optimize glycemic control in diabetes (DM). While electronic medical records provide a natural ground for detecting and analyzing hypoglycemia, ICD codes used in the databases may be invalid, insensitive or non-specific in detecting new hypoglycemic events. We developed text preprocessing methods to improve automatic detection of hypoglycemia from analysis of clinical encounter text notes.

METHODS

We set out to improve hypoglycemia detection from clinical notes by introducing three preprocessing methods: stop word filtering, medication signaling, and ICD narrative enrichment. To test the proposed methods, we selected clinical notes from VA Maryland Healthcare System, based on various combinations of three criteria that are suggestive of hypoglycemia, including ICD-9 code of diabetes and hypoglycemia, laboratory glucose values < 70 md/dL, and text reference to a proximate hypoglycemia event. In addition, we constructed one dataset of 395 clinical notes from year 2009 and another of 460 notes from year 2014 to test the generality of the proposed methods. For each of the datasets, two physician judges manually reviewed individual clinical notes to determine whether hypoglycemia was present or absent. A third physician judge served as a final adjudicator for disagreements.

RESULTS

Each of the proposed preprocessing methods contributed to the performance of hypoglycemia detection by significantly increasing the F1 score in the range of 5.3∼7.4% on one dataset (p < .01). Among the methods, stop word filtering contributed most to the performance improvement (7.4%). Combining all the preprocessing methods led to greater performance gain (p < .001) compared with using each method individually. Similar patterns were observed for the other dataset with the F1 score being increased in the range of 7.7%∼9.4% by individual methods (p < .001). Nevertheless, combining the three methods did not yield additional performance gain.

CONCLUSION

The proposed text preprocessing methods improved the performance of hypoglycemia detection from clinical text notes. Stop word filtering achieved the most performance improvement. ICD narrative enrichment boosted the recall of detection. Combining the three preprocessing methods led to additional performance gains.

Low fasting glucose and future risks of major adverse outcomes in people without baseline diabetes or cardiovascular disease: a systematic review and meta-analysis

OBJECTIVE

To investigate the link between low fasting blood glucose levels and all-cause mortality and cardiovascular outcomes among people without baseline diabetes or cardiovascular disease.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed and Embase (1966-February 2019).

SELECTION CRITERIA

Prospective cohort studies were included for meta-analysis if they reported adjusted HRs with 95% CIs for associations between risk of all-cause mortality, stroke, major cardiovascular events, coronary heart disease and low fasting glucose levels (<4.6 mmol/L and/or 4.0 mmol/L, respectively) versus normal fasting glucose levels.

DATA EXTRACTION AND STATISTICAL ANALYSIS

Two independent reviewers extracted data from eligible studies. Heterogeneity was assessed by p value of χ² tests and I². We assessed four characteristics for each included study based on items developed by the US Preventive Task Force, as well as the modified checklist used in previous studies.

RESULTS

Eleven articles (consisting of 129 prospective cohort studies) with 2 674 882 participants without diabetes and cardiovascular disease at baseline were included in this meta-analysis. Pooled results from the random effects model showed increased risks of all-cause mortality (HR: 1.56; 95% CI 1.09 to 2.23), total stroke (HR: 1.08, 95% CI 1.03 to 1.13) and ischaemic stroke (HR: 1.06, 95% CI 1.01 to 1.10), and major cardiovascular events (HR: 1.05, 95% CI 1.03 to 1.07) among people with a fasting glucose <4.0 mmol/L, as compared with people with normal fasting glucose. The less stringent low fasting glucose level, <4.6 mmol/L, was not associated with increased risk of any endpoints.

DISCUSSION AND CONCLUSIONS

Among people without baseline diabetes or cardiovascular disease, a fasting blood glucose level of <4.0 mmol/L is associated with increased risk of all-cause mortality, major cardiovascular events and stroke.

The relationship between blood glucose and nocturnal supraventricular tachycardia attacks in non-diabetic patients

PURPOSE

Decrease in the blood glucose level may trigger the tachycardia or bradycardia because it has an arrhythmogenic effect on the heart. Our purpose in this study was to investigate whether the blood glucose level has an effect on patients who attended to the hospital with nocturnal supraventricular tachycardia (SVT).

METHODS

We included 151 patients in our study who have SVT history. Plasma glucose levels which were taken during night hours, electrolytes, and 12 lead electrocardiography were evaluated.

RESULTS

There were 105 patients without nocturnal SVT attack and 46 patients with nocturnal SVT attack. Patients with nocturnal SVT attack, blood glucose level, potassium, calcium, and hemoglobin levels were significantly lower, hs-CRP was significantly higher, basal cycle length (BCL) was significantly short, and QT interval was significantly longer. It was found that blood glucose (O.R. = 0.904, 95% GA 0.828-0.986, p = 0.023) and potassium levels (O.R. = 0.128, 95% GA 0.029-0.561, p = 0.006) and basal cycle length (BCL) (O.R. 0.988, 95% GA, 0.980-0.996, p = 0.005) values were in independently correlated with nocturnal SVT attacks.

CONCLUSION

The decrease in blood glucose level of the patients who are being followed with SVT diagnosis might trigger the nocturnal SVT attacks.

The association of glycated hemoglobin with mortality and ESKD among persons with diabetes and chronic kidney disease

CONTEXT

Diabetic kidney disease (DKD) is the leading cause of end stage kidney disease (ESKD) and is associated with a considerably shortened lifespan. While glucose-lowering therapy targeting glycated hemoglobin (HbA1c) <7% is proven to reduce the risk of developing DKD, its effects on complications of DKD are unclear.

OBJECTIVE

We examined the associations of HbA1c with risks of progression to ESKD and death within a clinic-based study of CKD. We hypothesized that higher HbA1c concentrations would be associated with increased risks of ESKD and death.

DESIGN AND SETTING

We studied 618 participants from the Seattle Kidney Study (mean eGFR 42 ml/min), 308 of whom had diabetes, and tested associations of baseline HbA1c with time to a composite outcome of initiation of renal replacement therapy or death.

RESULTS

During a median follow-up of 4.2 years, there were 343 instances of the composite outcome (11.5 per 100 person-years). Among participants with diabetes, in both crude and adjusted analyses, higher HbA1c levels (examined continuously or categorically) were not associated with the risk of the composite outcome (HR (95% CI): 0.99 (0.88, 1.10) per 1% additional HbA1c, p = 0.79). HbA1c was not associated with ESKD or mortality when the outcomes were examined separately, nor when stratified between insulin users and non-users.

CONCLUSION

In a referred population of established DKD, higher HbA1c was not associated with higher risk of ESKD or death. These data support current recommendations to be conservative with glycemic control among patients with advanced diabetes complications, such as CKD.

Temporal Trends of Severe Hypoglycemia and Subsequent Mortality in Patients with Advanced Diabetic Kidney Diseases Transitioning to Dialysis

Background: Patients with diabetic kidney disease (DKD) are at higher risk of hypoglycemia than diabetic patients without DKD. We aimed to investigate the temporal trends of severe hypoglycemia in advanced DKD patients transitioning to dialysis and examine risk factors associated with severe hypoglycemia. We also investigated the association of severe hypoglycemia episodes with one-year mortality after initiation of dialysis in patients with advanced DKD. Methods: Using the Taiwan National Health Insurance Research Database, 46,779 advanced DKD patients transitioning to dialysis (Peritoneal dialysis 4216, hemodialysis 42,563) between 1997 and 2011 were enrolled. We calculated the rates of severe hypoglycemia from 5 years before dialysis until 10 years after dialysis. Cox proportional hazard model was used to examine the risk factors of post end stage renal disease (ESRD) one-year hypoglycemia and post ESRD one-year mortality in advanced DKD patients transitioning to dialysis. Results: We found that 11.5% of advanced DKD patients had at least one episode of severe hypoglycemia the year leading up to dialysis initiation. Multivariate analysis revealed hemodialysis compared with peritoneal dialysis, stroke, use of sulfonylurea, glinide, and insulin were associated with higher risk of severe hypoglycemia one year after transitioning to dialysis. Increased frequency of severe hypoglycemia-related hospitalizations was associated with incrementally higher mortality risk one year after transitioning to dialysis (Pre-ESRD hypoglycemia: Hazard ratios: 1.28 (1.18–1.38, p < 0.001), 1.64 (1.49–1.81, p < 0.001) for one, two hypoglycemia-related hospitalizations, respectively; post-ESRD hypoglycemia: HRs of 1.56 (1.40–1.73, p < 0.001), 1.72 (1.39–2.12, p < 0.001) for one, two hypoglycemia-related hospitalizations, respectively (reference group: no hypoglycemia related hospitalization)). Conclusions: Among advanced DKD patients, we observed a progressive elevated risk of hypoglycemia during the critical dialysis transition period. Increased frequency of severe hypoglycemia-related hospitalizations was associated with higher mortality risk one year after transitioning to dialysis. Further study of glycemic management strategies which prevent hypoglycemia during the critical transition period are warranted.