Prolonged cardiac repolarisation during spontaneous nocturnal hypoglycaemia in children and adolescents with type 1 diabetes

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.

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.

Hypoglycaemia in type 1 diabetes mellitus: risks and practical prevention strategies

Hypoglycaemia, which occurs when blood levels of glucose fall below what is considered a normal range, is a well-known complication of insulin therapy in individuals with type 1 diabetes mellitus. Despite advances in diabetes mellitus management, hypoglycaemia has continued to affect the majority of these individuals, leading to suboptimal care and decreased quality of life. Multiple epidemiological studies have demonstrated the risks associated with hypoglycaemic events. With this understanding, various advances have been made in therapeutics for diabetes mellitus management. Diabetes mellitus education continues to form the foundation for management and prevention of hypoglycaemia. The advent of newer diabetes mellitus technologies and newer insulins herald improvements in management strategies and hypoglycaemia prevention. Improved understanding of these newer approaches is needed to ensure delivery of safe and effective care to individuals with type 1 diabetes mellitus, leading to reductions in both the short-term and long-term morbidity and mortality associated with hypoglycaemic events.

Non-invasive method for blood glucose monitoring using ECG signal

Introduction: Tight glucose monitoring is crucial for diabetic patients by using a Continuous Glucose Monitor (CGM). The existing CGMs measure the Blood Glucose Concentration (BGC) from the interstitial fluid. These technologies are quite expensive, and most of them are invasive. Previous studies have demonstrated that hypoglycemia and hyperglycemia episodes affect the electrophysiology of the heart. However, they did not determine a cohort relationship between BGC and ECG parameters.

Material and method: In this work, we propose a new method for determining the BGC using surface ECG signals. Recurrent Convolutional Neural Networks (RCNN) were applied to segment the ECG signals. Then, the extracted features were employed to determine the BGC using two mathematical equations. This method has been tested on 04 patients over multiple days from the D1namo dataset, using surface ECG signals instead of intracardiac signal.

Results: We were able to segment the ECG signals with an accuracy of 94% using the RCNN algorithm. According to the results, the proposed method was able to estimate the BGC with a Mean Absolute Error (MAE) of 0.0539, and a Mean Squared Error (MSE) of 0.1604. In addition, the linear relationship between BGC and ECG features has been confirmed in this paper.

Conclusion: In this paper, we propose the potential use of ECG features to determine the BGC. Additionally, we confirmed the linear relationship between BGC and ECG features. That fact will open new perspectives for further research, namely physiological models. Furthermore, the findings point to the possible application of ECG wearable devices for non-invasive continuous blood glucose monitoring via machine learning.

Blood glucose estimation based on ECG signal

Successful self-management of diabetes requires Continuous Glucose Monitors (CGMs). These CGMs have several limitations such as being invasive, expensive and limited in terms of use. Many techniques, in vain, have been proposed to overcome these limitations. Nowadays, with the help of the Internet of Medical Things (IoMT) technologies, researchers are working to find alternative solutions. They succeed to predict hypoglycemia and hyperglycemia peaks using Electrocardiogram (ECG) signals. However, they failed to use it to estimate the Blood Glucose Concentration (BGC) directly and in real time. Three patients with 08 days of measurements from the D1namo dataset contributed to the study. A new technique has been proposed to estimate the BGC curves based on ECG signals. We used a convolutional neural network to segment the different regions of ECG signals as well as we extracted ECG features that were required for the next step. Then, five regression models have been employed to estimate BGC using as input sixth ECG parameters. We were able to segment the ECG signals with an accuracy of 94% using the convolutional neural network algorithm. The best performance among all simulated models was provided by Exponential Gaussian Process Regression (GPR) with Root Mean Squared Error (RMSE) values of 0.32, 0.41, 0.67 and R-squared (R²) values of 98%, 80%, and 70% for patients 01, 02 and 03 respectively. The method indicates the potential use of ECG wearable devices as non-invasive for continuous blood glucose monitoring, which is affordable and durable.

Severe Hypoglycemia and Incidence of QT Interval Prolongation Among Adults With Type 2 Diabetes

CONTEXT

There is a paucity of large-scale epidemiological studies on the link between severe hypoglycemia (SH) and corrected QT (QTc) interval prolongation in type 2 diabetes (T2DM).

OBJECTIVE

To evaluate the association of SH with QTc prolongation in adults with T2DM.

METHODS

Prospective cohort analysis of participants enrolled in the ACCORD (Action to Control Cardiovascular Risk in Diabetes) study without QTc prolongation at baseline. SH was assessed over a 24-month period. Incident QTc prolongation was ascertained using follow-up electrocardiograms. Modified Poisson regression was used to generate the risk ratio (RR) and 95% CI for QTc prolongation.

RESULTS

Among 8277 participants (mean age 62.6 years [SD 6.5], 38.7% women, 62.8% White), 324 had ≥1 SH episode (3.9%). Over a median of 5 years, 517 individuals developed QTc prolongation (6.3%). Participants with SH had a 66% higher risk of QTc prolongation (RR 1.66, 95% CI 1.16-2.38). The incidence of QTc prolongation was 10.3% (27/261) and 14.3% (9/63) for participants with 1 and ≥2 SH, respectively. Compared with no SH, RRs for patients with 1 and ≥2 SH episodes were 1.57 (95% CI 1.04-2.39) and 2.01 (95% CI 1.07-3.78), respectively. Age modified the association of SH with QTc prolongation (PInteraction = .008). The association remained significant among younger participants (<61.9 years [median age]: RR 2.63, 95% CI 1.49-4.64), but was nonsignificant among older participants (≥61.9 years: RR 1.37, 95% CI 0.87-2.17).

CONCLUSION

In a large population with T2DM, SH was associated with an increased risk of QTc prolongation independently of other risk factors such as cardiac autonomic neuropathy. The association was strongest among younger participants.

Review of the Pathophysiologic and Clinical Aspects of Hypokalemia in Children and Young Adults: an Update

This article examines the regulatory function of the skeletal muscle, renal, and adrenergic systems in potassium homeostasis. The pathophysiologic bases of hypokalemia, systematic approach for an early diagnosis, and therapeutic strategy to avert life-threatening complications are highlighted. By promoting skeletal muscle uptake, intense physical exercise (post), severe trauma, and several toxins produce profound hypokalemia. Hypovolemia due to renal and extra-renal fluid losses and ineffective circulation activate secondary aldosteronism causing urinary potassium wasting. In addition to hypokalemic alkalosis, primary aldosteronism causes low-renin hypertension. Non-aldosterone mineralocorticoid activation leading to low-renin and low-aldosterone hypertension occurs in Liddle's syndrome and apparent mineralocorticoid excess. Although there is enzymatic inhibition of cortisol synthesis in congenital adrenal hyperplasia, precursors of aldosterone produce low-renin hypokalemic hypertension. In addition to the glucocorticoid effect, hypercortisolism activates mineralocorticoid receptors in Cushing's syndrome. Genetic mutations involving furosemide-sensitive Na+-K+-2Cl- co-transporters and thiazide-sensitive Na+-Cl- transporters result in (non-hypertensive) salt-wasting nephropathy. Proximal and distal renal tubular acidosis is associated with hypokalemia. Eating disorders causing hypokalemia include bulimia, laxative abuse, and diuretic misuse. Low urinary potassium (<15 mmol/day) and/or low urinary chloride (<20 mol/L) suggest a gastrointestinal pathology. Co-morbidity of hypokalemia with chronic pulmonary and cardiovascular diseases may increase the fatality rate.

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.

Risk stratification of cardiac arrhythmias and sudden cardiac death in type 2 diabetes mellitus patients receiving insulin therapy: A population-based cohort study

INTRODUCTION

Metabolic abnormalities may exacerbate the risk of adverse outcomes in patients with type 2 diabetes mellitus. The present study aims to assess the predictive value of HbA1c and lipid variability on the risks of sudden cardiac death (SCD) and incident atrial fibrillation (AF).

METHODS

The retrospective observational study consists of type 2 diabetic patients prescribed with insulin, who went to publicly funded clinics and hospitals in Hong Kong between January 1, 2009 and December 31, 2009. Variability in total cholesterol, low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), triglyceride, and HbA1c were assessed through their SD and coefficient of variation. The primary outcomes were incident (1) ventricular tachycardia/ventricular fibrillation, actual or aborted SCD and (2) AF.

RESULTS

A total of 23 329 patients (mean ± SD age: 64 ± 14 years old; 51% male; mean HbA1c 8.6 ± 1.3%) were included. On multivariable analysis, HbA1c, total cholesterol, LDL-C and triglyceride variability were found to be predictors of SCD (p < .05).

CONCLUSION

HbA1c and lipid variability were predictive of SCD. Therefore, poor glucose control and variability in lipid parameters in diabetic patients are associated with aborted or actual SCD. These observations suggest the need to re-evaluate the extent of glycemic control required for outcome optimization.

Can Resistance Exercise Be a Tool for Healthy Aging in Post-Menopausal Women with Type 1 Diabetes?

Due to improvements in diabetes care, people with type 1 diabetes (T1D) are living longer. Studies show that post-menopausal T1D women have a substantially elevated cardiovascular risk compared to those without T1D. As T1D may also accelerate age-related bone and muscle loss, the risk of frailty may be considerable for T1D women. Exercise and physical activity may be optimal preventative therapies to maintain health and prevent complications in this population: They are associated with improvements in, or maintenance of, cardiovascular health, bone mineral density, and muscle mass in older adults. Resistance exercise, in particular, may provide important protection against age-related frailty, due to its specific effects on bone and muscle. Fear of hypoglycemia can be a barrier to exercise in those with T1D, and resistance exercise may cause less hypoglycemia than aerobic exercise. There are currently no exercise studies involving older, post-menopausal women with T1D. As such, it is unknown whether current guidelines for insulin adjustment/carbohydrate intake for activity are appropriate for this population. This review focuses on existing knowledge about exercise in older adults and considers potential future directions around resistance exercise as a therapeutic intervention for post-menopausal T1D women.

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.

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 β2 -adrenoreceptor agonist also causes QT-interval prolongation. We hypothesized that the magnitude of electrophysiological changes induced by salbutamol and hypoglycaemia might relate to each other and that salbutamol could be used as a non-invasive screening tool for predicting an individual's electrophysiological response to hypoglycaemia.

METHODS

Eighteen individuals with Type 1 diabetes were administered 2.5 mg of nebulized salbutamol. Participants then underwent a hyperinsulinaemic-hypoglycaemic clamp (2.5 mmol/l for 1 h). During both experiments, heart rate and serum potassium (and catecholamines during the clamp) were measured and a high-resolution electrocardiogram (ECG) was recorded at pre-set time points. Cardiac repolarization was measured by QT-interval duration adjusted for heart rate (QTc ), T-wave amplitude (Tamp ), T-peak to T-end interval duration (Tp Tend ) and T-wave area symmetry (Tsym ). The maximum changes vs. baseline in both experiments were assessed for their linear dependence.

RESULTS

Salbutamol administration caused QTc and Tp Tend prolongation and a decrease in Tamp and Tsym . Hypoglycaemia caused increased plasma catecholamines, hypokalaemia, QTc and Tp Tend prolongation, and a decrease in Tamp and Tsym . No significant correlations were found between maximum changes in QTc [r = 0.15, 95% confidence interval (95% CI) -0.341 to 0.576; P = 0.553), Tp Tend (r = 0.075, 95% CI -0.406 to 0.524; P = 0.767), Tsym (r = 0.355, 95% CI -0.132 to 0.706; P = 0.149) or Tamp (r = 0.148, 95% CI -0.347 to 0.572; P = 0.558) in either experiment.

CONCLUSIONS

Both hypoglycaemia and salbutamol caused pro-arrhythmogenic electrophysiological changes in people with Type 1 diabetes but were not related in any given individual. Salbutamol does not appear useful in assessing an individual's electrophysiological response to hypoglycaemia.

Association between QTc interval prolongation and outcomes of diabetic foot ulcers: Data from a 4-year follow-up study in China

OBJECTIVES

To examine whether QTc interval prolongation is an independent risk factor of outcomes in patients with diabetic foot ulcers (DFU).

RESEARCH DESIGN AND METHODS

331 patients with type 2 diabetes and DFU hospitalized in a Chinese tertiary hospital were recruited. ECG was done at baseline and QTc interval was calculated through Bazett's formula. Participants were classified into 2 groups according to the QTc interval as prolonged (≥440 ms) or not (<440 ms). These patients were followed-up for an average of 48 months to observe the outcomes, including ulcer healing, ulcer recurrence, nonfatal cerebral or cardiovascular events (NCCVE), cerebral cardiovascular death, cardiac death and all-cause death. The associations between the risk of outcomes and QTc interval prolongation, as well as per 1-SD increase in QTc interval were analyzed by Cox proportional-hazards models.

RESULTS

In terms of the univariate Cox proportional hazard models, patients with QTc interval prolongation had a higher all-cause mortality (HR = 1.621, 95%CI: 1.040-2.526, P = .013), higher cardiac mortality (HR = 2.011 95%CI: 1.106-3.657, P = .019), higher cerebral cardiovascular mortality (HR = 1.525, 95%CI: 0.8151-2.852, P = .045). The multivariate analysis showed that QTc prolongation was an independent risk factor for cardiac death (HR = 5.465, 95%CI: 2.818-8.112, P = .039). Similar results were obtained when QTc interval was used as a continue variable, a 1-SD increase in QTc interval was associated with an 5.883 times risk for cardiac mortality (HR = 6.883, 95%CI: 4.153-9.613, P = .012). The association between QTc interval prolongation with ulcer healing, recurrence and NCCVE were not observed either in univariate or multivariate analysis (P > .05).

CONCLUSION

QTc interval prolongation was a plausible predictor for cardiac death in DFU patients, but it cannot accurately predict ulcer healing or recurrence.

The risks of nocturnal hypoglycaemia in insulin-treated diabetes

Over half of all episodes of severe hypoglycaemia (requiring external help) occur during sleep, but nocturnal hypoglycaemia is often asymptomatic and unrecognised. The precise incidence of nocturnal hypoglycaemia is difficult to determine with no agreed definition, but continuous glucose monitoring has shown that it occurs frequently in people taking insulin. Attenuation of the counter-regulatory responses to hypoglycaemia during sleep may explain why some episodes are undetected and more prolonged, and modifies cardiovascular responses. The morbidity and mortality associated with nocturnal hypoglycaemia is probably much greater than realised, causing seizures, coma and cardiovascular events and affecting quality of life, mood and work performance the following day. It may induce impaired awareness of hypoglycaemia. Cardiac arrhythmias that occur during nocturnal hypoglycaemia include bradycardia and ectopics that may provoke dangerous arrhythmias. Treatment strategies are discussed that may help to minimise the frequency of nocturnal hypoglycaemia.

Incidence of prolonged QTc and severe hypoglycemia in type 1 diabetes: the EURODIAB Prospective Complications Study

AIMS

To assess the independent role of severe hypoglycemia on 7-year cumulative incidence of prolonged QTc in a large cohort of patients with type 1 diabetes.

METHODS

People with type 1 diabetes recruited by the EURODIAB Prospective Complications Study who had normal QTc were examined at baseline and after 7 years with standardized methods (n = 1415; mean age ± SD 32.1 ± 9.6 years; diabetes duration 14.2 ± 8.8 years). Hypoglycemic episodes were assessed by a questionnaire. QTc was calculated according to Bazett's formula. In logistic regression analysis, we examined the role of severe hypoglycemia (none, 1-2, or 3 and more episodes/year) on the cumulative incidence of prolonged QTc, independently of age, sex, HbA1c, blood pressure, BMI, physical activity, distal symmetrical and autonomic neuropathy.

RESULTS

In total, 264/1415 (17%) patients had incident prolonged QTc. Compared to those with persistently normal QTc, a greater proportion of incident cases had 3 and more hypoglycemic episodes at baseline (16.3 vs 11.2%, p = 0.03) and after 7 years (15.2 vs 9.6%, p = 0.01). In logistic regression analysis, 3 or more episodes of severe hypoglycemia at baseline did not increase cumulative incidence of prolonged QTc (OR 1.34, 95% CI 0.88-2.03). By contrast, severe hypoglycemia at the follow-up examination was associated with higher incidence of QTc prolongation (OR 1.68, 1.09-2.58), which reverted to not significant after adjustment for diabetic neuropathy.

CONCLUSIONS

Severe hypoglycemia was not associated with incidence QTc prolongation in type 1 diabetic patients from the EURODIAB PCS.

A Case of Hypoglycemiainduced QT Prolongation Leading to Torsade de Pointes and a Review of Pathophysiological Mechanisms

Torsades de pointes is a life-threatening cardiac arrhythmia. Occurrence of this arrhythmia as a result of hypoglycemia has not been reported in the literature. We describe an interesting case of an insulin-dependent diabetic patient presenting with torsades de pointes resulting from hypoglycemia. A 62-year-old male was admitted to the hospital following an episode of severe insulin-induced hypoglycemia and a cardiac arrest. He was found to unresponsive at home after taking insulin. His serum glucose was found to be 18. He was given juice initially to normalize his glucose and was then transferred by EMS to ER where he was given 5% dextrose infusion. Analysis of the LifeVest rhythm recording showed torsades de pointes that was terminated by defibrillation of the LifeVest. Several mechanisms are responsible for torsade, including QT interval prolongation, adrenalin secretion and calcium overload leading to intracellular calcium oscillations. These mechanisms are a trigger to torsade de pointes. Predisposing factors were present leading torsade to occur.

Changes in cardiac repolarisation during spontaneous nocturnal hypoglycaemia in subjects with type 1 diabetes: a preliminary report

AIMS

Experimental studies have revealed that hypoglycaemia can result in morphological changes in electrocardiographic repolarisation in subjects with type 1 diabetes. However, the influence of spontaneous nocturnal hypoglycaemia on repolarisation morphology in a 'real life' situation is not clear.

METHODS

Adults with type 1 diabetes (n = 11) underwent continuous glucose monitoring with a subcutaneous sensor and digital 12-lead ECG recording for three nights. T-wave morphology was analysed with custom-made software during both hypoglycaemia (glucose <3.5 mmol/l at least 20 min) from ten consecutive heart beats in the middle of the deepest hypoglycaemia and from a control nonhypoglycaemic period (glucose ≥5.0 mmol/l) from the same recording.

RESULTS

In the comparison of 10 hypoglycaemia-control pairs, heart rate (65 ± 12 beats/min during normoglycaemia versus 85 ± 19 beats/min during hypoglycaemia, p = 0.028) increased and the QT_c interval (439 ± 5 vs. 373 ± 5 ms, respectively, p = 0.025) decreased significantly during hypoglycaemia. The spatial QRS-T angle (TCRT) was reduced, and the roughness of the T-wave loop (T-E) increased significantly (p = 0.037 for both) in the patients during hypoglycaemia.

CONCLUSIONS

In adults with type 1 diabetes, spontaneous nocturnal hypoglycaemia results in morphological changes and increased heterogeneity of global cardiac repolarisation. These changes may contribute to the risk of 'dead in bed' syndrome encountered in young individuals with type 1 diabetes.

QT prolongation caused by insulin-induced hypoglycaemia - An interventional study in 119 individuals

AIMS

Hypoglycaemia is associated with increased risk of cardiovascular events and mortality in patients with diabetes, but the extent and mechanisms of this link are ill defined. We here prospectively studied cardiac repolarization abnormalities during insulin-induced hypoglycaemia in humans.

METHODS

119 individuals (69 males, age 47.5±13.4years, range 18-82years) were assessed during hypoglycaemia after the injection of 0.1-0.25units/kg human insulin. Corrected QT intervals (QTc) and QT dispersion (QTd) were calculated from serially recorded twelve lead electrocardiograms, and plasma glucose and other endocrine markers were studied.

RESULTS

QTc increased from 415.1±21.9ms (mean±standard deviation) at baseline to 444.9±26.5ms during hypoglycaemia (plasma glucose nadir, 1.6±0.5mmol/L, p=0.001), accompanied by an increase of QTd from 45.0±22.7ms to 64.1±40.0ms (p<0.001). Hypoglycaemia-induced abnormal QTc prolongation (defined as ⩾460ms in females and ⩾450ms in males) occurred in 17% (9/54) of females and 26% (17/65) of males. 97 of 119 of individuals (82%) developed transient hypokalaemia (K⁺ ⩽3.6mmol/L), and plasma epinephrine increased from 220.4±169.5pmol/L at baseline to 2945.6±2421.4pmol/L during hypoglycaemia. Baseline QTc, but not age or gender, was a significant predictor of hypoglycaemia-induced QTc prolongation (p=0.001).

CONCLUSIONS

Insulin-induced hypoglycaemia frequently causes abnormal QT prolongation and is associated with hypokalaemia and sympathoadrenal activation, thereby increasing the potential risk for ventricular arrhythmias, particularly in individuals with pre-existing high normal QTc.

QT interval, corrected for heart rate, is associated with HbA1c concentration and autonomic function in diabetes

AIMS

To examine QT intervals corrected for heart rate (QTc) in adolescents with Type 1 diabetes compared with control subjects, and to determine associations with metabolic control and autonomic function.

METHODS

Resting electrocardiogram recordings of 142 adolescents with Type 1 diabetes [mean (sd) age 15.3 (2.0) years, diabetes duration 9.0 (3.5) years, HbA1c 71 (17) mmol/mol or 8.7 (1.6)%] and 125 control subjects [mean (sd) age 15.7 (2.5) years] were used to calculate QTc duration and derive mean heart rate and heart rate variability (HRV) values. Linear and logistic regression models were used to examine the associations between QTc, metabolic control and autonomic function (HRV and pupillary function).

RESULTS

QTc duration was not significantly different between subjects with Type 1 diabetes and control subjects (mean duration 392 vs 391 ms; P = 0.65). In the Type 1 diabetes group, QTc was positively associated with HbA1c [β = 4 (95% CI 2, 6); P < 0.001] and inversely associated with severe hypoglycaemic events [β = -10 (95% CI -20,-2); P = 0.01], less insulin/kg [β = -12 (95% CI -22, -2); P = 0.024] and less HRV. In the Type 1 diabetes group, QTc in the highest quintile (≥409 ms) vs quintiles 1-4 had more pupillary abnormalities (83 vs 56%; P = 0.03), lower pupillary maximum constriction velocity (4.8 vs 5.3 mm/s; P = 0.04), higher heart rate (78 vs 72 beats per min; P = 0.02) and lower HRV (standard deviation of mean NN intervals 4.0 vs 4.3 ms, P = 0.004 and root-mean-square difference of successive NN intervals 3.7 vs 4.1 ms; P = 0.004).

CONCLUSIONS

Although there are concerns about hypoglycaemia in general in people with Type 1 diabetes, chronic hyperglycaemia, rather than intermittent hypoglycaemia, appears to be more deleterious to autonomic cardiac function, even in adolescence. Longer QTc was associated with higher HbA1c concentration, lower risk of hypoglycaemia and autonomic dysfunction. Longitudinal studies are warranted.

Diabetic autonomic neuropathy

Diabetes mellitus is the commonest cause of an autonomic neuropathy in the developed world. Diabetic autonomic neuropathy causes a constellation of symptoms and signs affecting cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory, and sudomotor systems. Several discrete syndromes associated with diabetes cause autonomic dysfunction. The most prevalent of these are: generalized diabetic autonomic neuropathy, autonomic neuropathy associated with the prediabetic state, treatment-induced painful and autonomic neuropathy, and transient hypoglycemia-associated autonomic neuropathy. These autonomic manifestations of diabetes are responsible for the most troublesome and disabling features of diabetic peripheral neuropathy and result in a significant proportion of the mortality and morbidity associated with the disease.

Considerations for assessing the potential effects of antidiabetes drugs on cardiac ventricular repolarization: A report from the Cardiac Safety Research Consortium

Thorough QT studies conducted according to the International Council on Harmonisation E14 guideline are required for new nonantiarrhythmic drugs to assess the potential to prolong ventricular repolarization. Special considerations may be needed for conducting such studies with antidiabetes drugs as changes in blood glucose and other physiologic parameters affected by antidiabetes drugs may prolong the QT interval and thus confound QT/corrected QT assessments. This review discusses potential mechanisms for QT/corrected QT interval prolongation with antidiabetes drugs and offers practical considerations for assessing antidiabetes drugs in thorough QT studies. This article represents collaborative discussions among key stakeholders from academia, industry, and regulatory agencies participating in the Cardiac Safety Research Consortium. It does not represent regulatory policy.

High risk of abnormal QT prolongation in the early morning in diabetic and non-diabetic patients with severe hypoglycemia

BACKGROUND

Several studies have suggested that the occurrence of severe hypoglycemia during sleep may be more dangerous for cardiac arrhythmia than that in the day-time.

METHODS

We performed a retrospective study between January 2006 and March 2012 to assess electrocardiograms during severe hypoglycemia in patients with or without diabetes.

RESULTS

A total of 59,602 patients who visited the emergency room by ambulance were screened, and 287 patients with severe hypoglycemia were enrolled. The median blood glucose levels in patients with (DM, n = 192) and without diabetes (non-DM, n = 95) were 30 and 45 mg/dL, respectively. During severe hypoglycemia, the incidence of abnormal QT prolongation was significantly higher in the early morning (4-10 a.m.) than at other times (DM group, 74.3% versus 54.1%, P = 0.02; non-DM group, 78.3% versus 50.0%, P = 0.01). Multivariate logistic regression analysis identified the occurrence of severe hypoglycemia in the early morning as a strong factor for abnormal QT prolongation (DM group, odds ratio [OR] 2.80, 95% confidence interval [CI] 1.15-6.80, P = 0.02; non-DM group, OR 4.53, 95% CI 1.30-15.74, P = 0.01).

CONCLUSIONS

The incidence of abnormal QT prolongation during severe hypoglycemia was significantly higher in the early morning than at all other times, independent of the cause of severe hypoglycemia.

Heart rate-corrected QT interval prolongation as a prognostic marker for 3-year survival in people with Type 2 diabetes undergoing above-ankle amputation

AIM

To evaluate whether heart rate-corrected QT interval is a plausible prognostic factor for survival after major amputation in people with Type 2 diabetes.

METHODS

All people with Type 2 diabetes aged < 80 years who underwent a major amputation at two hospitals with multidisciplinary diabetic foot teams were evaluated and grouped according to whether their heart rate-corrected QT interval was  ≤  or  > 440 ms.

RESULTS

A total of 70 patients with a median age of 72 years were included in the study. During the 3 years of follow-up, 38 patients (54%) died. Heart rate-corrected QT interval prolongation was present in 51.4% of the patients and was strongly associated with 3-year mortality (73 vs 36%; P < 0.001). In a Cox proportional hazard model, heart rate-corrected QT interval prolongation was the strongest independent risk factor for 3-year mortality [hazard ratio 2.20 (95% CI 1.11-4.38)]. Treatment with metformin seemed to have a protective effect [hazard ratio 0.22 (95% CI 0.05-0.94)].

CONCLUSIONS

The findings of the present study indicate that heart rate-corrected QT interval prolongation is associated with increased mortality in people with Type 2 diabetes undergoing above-ankle amputation.

Hypoglycaemia and QT interval prolongation in type 1 diabetes--bridging the gap between clamp studies and spontaneous episodes

AIMS

We propose a study design with controlled hypoglycaemia induced by subcutaneous injection of insulin and matched control episodes to bridge the gap between clamp studies and studies of spontaneous hypoglycaemia. The observed prolongation of the heart rate corrected QT interval (QTc) during hypoglycaemia varies greatly between studies.

METHODS

We studied ten adults with type 1 diabetes (age 41±15years) without cardiovascular disease or neuropathy. Single-blinded hypoglycaemia was induced by a subcutaneous insulin bolus followed by a control episode on two occasions separated by 4weeks. QT intervals were measured using the semi-automatic tangent approach, and QTc was derived by Bazett's (QTcB) and Fridericia's (QTcF) formulas.

RESULTS

QTcB increased from baseline to hypoglycaemia (403±20 vs. 433±39ms, p<0.001). On the euglycaemia day, QTcB also increased (398±20 vs. 410±27ms, p<0.01), but the increase was less than during hypoglycaemia (p<0.001). The same pattern was seen for QTcF. Plasma adrenaline levels increased significantly during hypoglycaemia compared to euglycaemia (p<0.01). Serum potassium levels decreased similarly after insulin injection during both hypoglycaemia and euglycaemia.

CONCLUSIONS

Hypoglycaemia as experienced after a subcutaneous injection of insulin may cause QTc prolongation in type 1 diabetes. However, the magnitude of prolongation is less than typically reported during glucose clamp studies, possible because of the study design with focus on minimizing unwanted study effects.

Evolvable rough-block-based neural network and its biomedical application to hypoglycemia detection system

This paper focuses on the hybridization technology using rough sets concepts and neural computing for decision and classification purposes. Based on the rough set properties, the lower region and boundary region are defined to partition the input signal to a consistent (predictable) part and an inconsistent (random) part. In this way, the neural network is designed to deal only with the boundary region, which mainly consists of an inconsistent part of applied input signal causing inaccurate modeling of the data set. Owing to different characteristics of neural network (NN) applications, the same structure of conventional NN might not give the optimal solution. Based on the knowledge of application in this paper, a block-based neural network (BBNN) is selected as a suitable classifier due to its ability to evolve internal structures and adaptability in dynamic environments. This architecture will systematically incorporate the characteristics of application to the structure of hybrid rough-block-based neural network (R-BBNN). A global training algorithm, hybrid particle swarm optimization with wavelet mutation is introduced for parameter optimization of proposed R-BBNN. The performance of the proposed R-BBNN algorithm was evaluated by an application to the field of medical diagnosis using real hypoglycemia episodes in patients with Type 1 diabetes mellitus. The performance of the proposed hybrid system has been compared with some of the existing neural networks. The comparison results indicated that the proposed method has improved classification performance and results in early convergence of the network.

The proarrhythmic effect of hypoglycemia: evidence for increased risk from ischemia and bradycardia

Hypoglycemia increases the risk for both overall and sudden death. At a cellular level, hypoglycemia causes alterations in the physiology of myocardial tissue that are identical to proarrhythmic medications. Reduced serum glucose blocks the repolarizing K(+) channel HERG, which leads to action potential and QT prolongation and is uniformly associated with risk for torsades de pointes ventricular tachycardia. The sympathetic response induced by hypoglycemia also increases the risk of arrhythmias from Ca(2+) overload, which occur with sympathomimetic medications and excessive beta adrenergic stimulation. Thus, hypoglycemia can be considered a proarrhythmic event. This review focuses on emerging evidence for two other important changes induced by hypoglycemia that promote arrhythmias: ischemia and bradycardia. Studies of patients with "insulin shock" therapy from the early twentieth century and other more recent data strongly suggest that hypoglycemia can cause ischemia of myocardial tissue, both in association with coronary artery obstructions and by cellular mechanisms. Ischemia induces multiple proarrhythmic responses. Since ischemia itself reduces the possibility of using energy substrates other than glucose, hypoglycemia may generate positive feedback for electrophyisologic destabilization. Recent studies also show that hypoglycemia can cause bradycardia and heart block. Bradycardia is known to cause action potential prolongation and potentiate the development of torsades de pointes, particularly with low-serum K(+) which can be induced by hypoglycemic episodes. Thus, hypoglycemia-induced bradycardia may also create a dynamic, positive feedback for the development of arrhythmias and sudden death. These studies further support the hypothesis that hypoglycemia is a proarrhythmic event.

Cardiac implications of hypoglycaemia in patients with diabetes - a systematic review

BACKGROUND

Hypoglycaemia has been associated with increased cardiovascular (CV) risk and mortality in a number of recent multicentre trials, but the mechanistic links driving this association remain ill defined. This review aims to summarize the available data on how hypoglycaemia may affect CV risk in patients with diabetes.

METHODS

This was a systematic review of available mechanistic and clinical studies on the relationship between hypoglycaemia and cardiovascular risk. Study outcomes were compiled from relevant articles, and factors contributing to hypoglycaemia-mediated CVD and its complications are discussed.

RESULTS

Six recent comprehensive clinical trials have reinforced the critical importance of understanding the link between hypoglycaemia and the CV system. In addition, 88 studies have indicated that hypoglycaemia mechanistically contributes to CV risk by increasing thrombotic tendency, causing abnormal cardiac repolarization, inducing inflammation, and contributing to the development of atherosclerosis. These hypoglycaemia-associated risk factors are conducive to events such as unstable angina, non-fatal and fatal myocardial infarction, sudden death, and stroke in patients with diabetes.

CONCLUSIONS

Emerging data suggest that there is an impact of hypoglycaemia on CV function and mechanistic link is multifactorial. Further research will be needed to ascertain the full impact of hypoglycaemia on the CV system and its complications.

Identification of hypoglycemia and hyperglycemia in type 1 diabetic patients using ECG parameters

Hypoglycemia and Hyperglycemia are both serious diseases related to diabetes mellitus. Among Type 1 Diabetic patients, there are who experience both hypoglycemic and hyperglycemic events. The aim of this study was to identify of hypoglycemia and hyperglycemia based on ECG changes in this population. An ECG Acquisition and Analysis System based on LabVIEW software has been developed for collecting ECG signals and extracting features with abnormal changes. ECG parameters included Heart rate (HR), corrected QT interval (QTeC), PR interval, corrected RT interval (RTC) and corrected TpTe interval (TpTe(C)). Blood glucose levels were used to classify glycemic states in subjects as hypoglycemic state (≤ 60 mml/l, Hypo), as normoglycemic state (80 to 110 mmol/l, Normo), and as hyperglycemic state 150 mml/l, Hyper). The results indicated that hypoglycemic and hyperglycemic states produce significant inverse changes on those ECG parameters.

The impact of metabolic control and QTc prolongation on all-cause mortality in patients with type 2 diabetes and foot ulcers

AIMS/HYPOTHESIS

The increased all-cause mortality in patients with chronic diabetic foot ulcers cannot fully be explained by traditional cardiovascular risk factors. The significance of heart-rate-corrected QT (QTc) prolongation, a finding often seen in these patients, is unknown. Recently, the importance of metabolic control and hypoglycaemia has been discussed. The aim of this study was to evaluate the impact of different HbA1c levels and QTc prolongation on all-cause mortality in the high-risk population of patients with type 2 diabetes mellitus and foot ulcers.

METHODS

All patients with type 2 diabetes, younger than 80 years, visiting our diabetes foot unit, with a foot ulcer duration >4 weeks, were screened for participation. Patients on dialysis were excluded. Patients were grouped according to HbA1c level and QTc time ≤ or > 440 ms.

RESULTS

Patients (n = 214, median age 69.1 years) were grouped according to HbA1c level (HbA1c < 7.5% [<58 mmol/mol] n = 81, 7.5-8.9% [58-74 mmol/mol] n = 70, >8.9% [>74 mmol/mol] n = 63). Baseline characteristics, including use of potential hypoglycaemic drugs, were similar between groups. During the 8 years of follow-up 151 patients died (70.6%) and HbA1c < 7.5% (<58 mmol/mol) was strongly associated with increased mortality. The highest mortality was seen in patients with a combination of HbA1c < 7.5% (<58 mmol/mol) and QTc prolongation, with an 8 year mortality of 92.1% as compared with 48.8% in those with HbA1c < 7.5% (<58 mmol/mol) but without QTc prolongation. CONCLUSION/INTERPRETATIONS: HbA1c < 7.5% (<58 mmol/mol) in a high-risk population of patients with type 2 diabetes and foot ulcers is associated with a significantly higher mortality, particularly in patients with QTc prolongation.

Hypoglycemia-associated autonomic failure in diabetes

The concept of hypoglycemia-associated autonomic failure (HAAF) in diabetes posits that recent antecedent hypoglycemia, as well as sleep or prior exercise, causes both defective glucose counterregulation (by attenuating the adrenomedullary epinephrine response, in the setting of absent insulin and glucagon responses) and hypoglycemia unawareness (by attenuating the sympathoadrenal, largely the sympathetic neural, response) and thus a vicious cycle of recurrent hypoglycemia. Albeit with different time courses, the pathophysiology of defense against hypoglycemia - no decrease in therapeutic insulin, no increase in glucagon and an attenuated increase in sympathoadrenal activity - is the same in type 1 diabetes and advanced type 2 diabetes. Hypoglycemia unawareness is reversible by 2-3 weeks of scrupulous avoidance of hypoglycemia in most affected patients. The pathophysiology of HAAF in diabetes explains why the incidence of hypoglycemia increases as patients approach the absolute endogenous insulin deficient end of the disease, provides a comprehensive set of risk factors including those indicative of HAAF, and leads logically to the practice of hypoglycemia risk factor reduction. Because of the risk of hypoglycemic mortality, presumably from cardiac arrhythmias, glycemic goals in diabetes should be individualized, based in part on the risk of hypoglycemia. By practicing hypoglycemia risk reduction - addressing the issue, applying the principles of aggressive glycemic therapy and considering both the conventional risk factors and those indicative of HAAF - it is possible to both improve glycemic control and reduce the risk of hypoglycemia in many patients with diabetes.

Hypoglycemia, diabetes, and cardiovascular disease

Cardiovascular disease (CVD) remains the leading cause of death in people with diabetes, and the risk of CVD for adults with diabetes is at least two to four times the risk in adults without diabetes. Complications of diabetes, including not only CVD but also microvascular diseases such as retinopathy and nephropathy, are a major health and financial burden. Diabetes is a disease of glucose intolerance, and so much of the research on complications has focused on the role of hyperglycemia. Clinical trials have clearly demonstrated the role of hyperglycemia in microvascular complications of diabetes, but there appears to be less evidence for as strong of a relationship between hyperglycemia and CVD in people with diabetes. Hypoglycemia has become a more pressing health concern as intensive glycemic control has become the standard of care in diabetes. Clinical trials of intensive glucose lowering in both type 1 and type 2 diabetes populations has resulted in significantly increased hypoglycemia, with no decrease in CVD during the trial period, although several studies have shown a reduction in CVD with extended follow-up. There is evidence that hypoglycemia may adversely affect cardiovascular risk in patients with diabetes, and this is one potential explanation for the lack of CVD prevention in trials of intensive glycemic control. Hypoglycemia causes a cascade of physiologic effects and may induce oxidative stress and cardiac arrhythmias, contribute to sudden cardiac death, and cause ischemic cerebral damage, presenting several potential mechanisms through which acute and chronic episodes of hypoglycemia may increase CVD risk. In this review, we examine the risk factors and prevalence of hypoglycemia in diabetes, review the evidence for an association of both acute and chronic hypoglycemia with CVD in adults with diabetes, and discuss potential mechanisms through which hypoglycemia may adversely affect cardiovascular risk.

Ventricular repolarization variability for hypoglycemia detection

Hypoglycemia is the most acute and common complication of Type 1 diabetes and is a limiting factor in a glycemic management of diabetes. In this paper, two main contributions are presented; firstly, ventricular repolarization variabilities are introduced for hypoglycemia detection, and secondly, a swarm-based support vector machine (SVM) algorithm with the inputs of the repolarization variabilities is developed to detect hypoglycemia. By using the algorithm and including several repolarization variabilities as inputs, the best hypoglycemia detection performance is found with sensitivity and specificity of 82.14% and 60.19%, respectively.

Electrocardiographic signals and swarm-based support vector machine for hypoglycemia detection

Cardiac arrhythmia relating to hypoglycemia is suggested as a cause of death in diabetic patients. This article introduces electrocardiographic (ECG) parameters for artificially induced hypoglycemia detection. In addition, a hybrid technique of swarm-based support vector machine (SVM) is introduced for hypoglycemia detection using the ECG parameters as inputs. In this technique, a particle swarm optimization (PSO) is proposed to optimize the SVM to detect hypoglycemia. In an experiment using medical data of patients with Type 1 diabetes, the introduced ECG parameters show significant contributions to the performance of the hypoglycemia detection and the proposed detection technique performs well in terms of sensitivity and specificity.

Dynamic estimation of cardiac repolarization characteristics during hypoglycemia in healthy and diabetic subjects

Hypoglycemia is known to affect the repolarization characteristics of the heart, but the mechanisms behind these changes are not completely understood. We analyzed repolarization characteristics continuously from 22 subjects during normoglycemic period, transition period (blood glucose concentration decreasing) and hypoglycemic period from nine healthy controls (Healthy), six otherwise healthy type 1 diabetics (T1DM) and seven type 1 diabetics with disease complications (T1DMc). An advanced principal component regression (PCR)-based method was used for estimating ECG parameters beat-by-beat, and thus, continuous comparison between the repolarization characteristics and blood glucose values was made. We observed that hypoglycemia related ECG changes in the T1DMc group were smaller than changes in the Healthy and T1DM groups. We also noticed that when glucose concentration remained at a low level, the heart rate corrected QT interval prolonged progressively. Finally, a few minutes time lag was observed between the start of hypoglycemia and cardiac repolarization changes. One explanation for these observations could be that hypoglycemia related hormonal changes have a significant role behind the repolarization changes. This could explain at least the observed time lag (hormonal changes are slow) and the lower repolarization changes in the T1DMc group (hormonal secretion lowered in long duration diabetics).

Electrocardiographic T-wave peak-to-end interval for hypoglycaemia detection

Electrocardiographic T wave peak-to-end interval (TpTe) is one parameter of T wave morphology, which contains indicators for hypoglycaemia. This paper shows the corrected TpTe (TpTe(c)) interval as one of the inputs contributing to detect hypoglycaemia. Support vector machine (SVM) and fuzzy support vector machine (FSVM) utilizing radial basis function (RBF) are used as the classification methods in this paper. By comparing with the classification systems using inputs of corrected QT interval (QT(c)) and heart rate only, the results indicate that the inclusion of TpTec in combination with QTc and heart rate performs better in the detection of hypoglycaemia in terms of sensitivity, specificity and accuracy.

Sleep and the response to hypoglycaemia

Undetected nocturnal hypoglycaemia frequently occurs in patients with diabetes, having a negative influence on well-being, counterregulation against and awareness of subsequent hypoglycaemia, and even causing sudden death in some cases most likely by inducing cardiac arrhythmia. Sleep markedly weakens the neuroendocrine defence mechanism against hypoglycaemia by shifting the glycaemic threshold for counterregulatory activation to lower levels. While hypoglycaemia triggers awakening in healthy subjects, patients with type 1 diabetes frequently fail to awake in the presence of low plasma glucose levels. Little is known about the frequency of and responses to nocturnal hypoglycaemia in patients with type 2 diabetes. Unfortunately, effective strategies to prevent or even safely detect nocturnal hypoglycaemia are still lacking. Taken together, hypoglycaemia occurring during sleep presents a major, often neglected problem in the management of diabetic patients. Different aspects of this phenomenon such as responses to and consequences of nocturnal hypoglycaemia as well as strategies for its prevention are highlighted in this review.

QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

AIMS/HYPOTHESIS

Prolongation of the heart rate corrected QT interval (QTc) is seen during episodes of hypoglycaemia in type 1 diabetes. We studied the relationship between spontaneous hypoglycaemia and the QT interval and hypothesised that the choice of heart rate correction affects the observed change in QTc.

METHODS

Twenty-one participants with type 1 diabetes (aged 58 +/- 10 years with duration of diabetes 34 +/- 12 years) had continuous glucose and ECG monitoring for 72 h. QT and RR intervals were measured during hypoglycaemia (blood glucose or continuous glucose measurements <or=3.5 mmol/l) and compared with euglycaemia (5-12 mmol/l). QT intervals were measured using the semi-automated tangent method from signal-averaged ECG and corrected using Bazett's formula, Fridericia's formula, the nomogram method and a linear subject-specific method.

RESULTS

Hypoglycaemia was present in 14 participants. With Bazett's formula, QTc changed significantly from euglycaemia to hypoglycaemia (422 +/- 30 vs 432 +/- 33 ms; p = 0.02). Heart rate, QT intervals and QTc corrected with formulas other than Bazett's were not associated with a significant change (p = 0.07-0.29). During hypoglycaemia, significantly lower values of QTc compared with the subject-specific method were seen for Fridericia's formula (p = 0.02) and the nomogram method (p = 0.04).

CONCLUSIONS/INTERPRETATION

Spontaneous hypoglycaemia was associated with a modest increase in QTc. Bazett's formula resulted in overcorrection of QTc while both Fridericia's formula and the nomogram method undercorrected the QTc compared with the subject-specific method during hypoglycaemia. The results may indicate that the use of a fixed heart rate correction formula can lead to misleading results in investigations of spontaneous hypoglycaemia.

The case for hypoglycaemia as a proarrhythmic event: basic and clinical evidence

Recent clinical studies show that hypoglycaemia is associated with increased risk of death, especially in patients with coronary artery disease or acute myocardial infarction. This paper reviews data from cellular and clinical research supporting the hypothesis that acute hypoglycaemia increases the risk of malignant ventricular arrhythmias and death in patients with diabetes by generating the two classic abnormalities responsible for the proarrhythmic effect of medications, i.e. QT prolongation and Ca(2+) overload. Acute hypoglycaemia causes QT prolongation and the risk of ventricular tachycardia by directly suppressing K(+) currents activated during repolarisation, a proarrhythmic effect of many medications. Since diabetes itself, myocardial infarction, hypertrophy, autonomic neuropathy and congestive heart failure also cause QT prolongation, the arrhythmogenic effect of hypoglycaemia is likely to be greatest in patients with pre-existent cardiac disease and diabetes. Furthermore, the catecholamine surge during hypoglycaemia raises intracellular Ca(2+), thereby increasing the risk of ventricular tachycardia and fibrillation by the same mechanism as that activated by sympathomimetic inotropic agents and digoxin. Diabetes itself may sensitise myocardium to the arrhythmogenic effect of Ca(2+) overload. In humans, noradrenaline (norepinephrine) also lengthens action potential duration and causes further QT prolongation. Finally, both hypoglycaemia and the catecholamine response acutely lower serum K(+), which leads to QT prolongation and Ca(2+) loading. Thus, hypoglycaemia and the subsequent catecholamine surge provoke multiple, interactive, synergistic responses that are known to be proarrhythmic when associated with medications and other electrolyte abnormalities. Patients with diabetes and pre-existing cardiac disease may therefore have increased risk of ventricular tachycardia and fibrillation during hypoglycaemic episodes.

Diabetes and Cardiovascular Disease: Is intensive glucose control beneficial or deadly? Lessons from ACCORD, ADVANCE, VADT, UKPDS, PROactive, and NICE-SUGAR

Type 2 diabetes is a rather complex metabolic disorder still associated with a 2-fold increased cardiovascular (CV) mortality despite a dramatic improvement in CV risk reduction by multifactorial intervention strategies. Intensive glucose control can also reduce CV morbidity, but this effect seems to be limited to younger patients with shorter duration of disease and no CV disease. Intensive glucose control--in particular when complex insulin strategies are used--is associated with a 5-fold increased risk for severe hypoglycemia, which could induce harm in some patients. In contrast to blood pressure and lipid-lowering interventions a reduction of CV mortality cannot be seen before 10-20 years after the start of the glucose-lowering intervention (metabolic memory, legacy effect). Future ongoing outcome studies in more than 50,000 patients will clarify whether new antidiabetic drugs--not inducing hypoglycemia or weight gain--will further improve the prognosis of T2DM patients.

Parental attitudes towards overnight closed-loop glucose control in children with type 1 diabetes

BACKGROUND

This study examined parental attitudes towards overnight closed-loop (CL) glucose control in children and young people with type 1 diabetes (T1D).

METHODS

Twelve families recruited by the INsulin PUmp Therapy group (INPUT), a U.K. patient/carer-led support group for people with T1D, attended a focus meeting on CL. The concept of CL was explained, and clinical results and plans regarding the Artificial Pancreas Project at Cambridge were presented. Participants completed a questionnaire to evaluate parental feelings about T1D management and attitudes towards overnight CL insulin delivery.

RESULTS

Nineteen parents (12 mothers and seven fathers) anonymously completed the questionnaire. Main concerns about diabetes were related to long-term complications (84%) and hypoglycemia (16%). Achieving good glucose control represented major challenge for carers (83%) with nighttime being the most difficult period to manage (56%), worrying most parents (71%) particularly because of fear of hypoglycemia (33%). The development of CL to manage diabetes was welcomed by all parents (100%) with 95% happy for their child to wear a continuous glucose monitor together with an insulin pump. All parents were ready to respond to additional alarms at night with 90% parents not worried about their child's overnight insulin delivery being controlled by a computer.

CONCLUSIONS

Selected parents of children with T1D who are already insulin pump users express implied trust in the technology for overnight CL insulin delivery. Nighttime blood glucose control is the biggest challenge and concern for parents, and the development of a commercially available overnight CL system may be an important goal.