Hypoglycaemia and associated hypokalaemia in diabetes: mechanisms, clinical implications and prevention

Strong independent association between third-degree AV-block and diabetes mellitus using a large database

BACKGROUND

Recent data suggests an association between DM and third-degree AV- Block. The goal of this study was to evaluate the independent association between diabetes and third-degree AV-Block using a very large database.

METHOD

We used ICD-9 Codes for DM and third-degree AV-block from the Nationwide Inpatient Sample (NIS) database. We randomly selected the 1992 and 2002 databases which are 10 years apart as two independent samples. We used uni- and multi-variate analysis to evaluate this association.

RESULTS

1992 database contained a total of 6,195,744 patients. Diabetes occurred in (0.5 %) of patients with third-degree AV-block vs. (0.2 %) of the control (OR: 2.15, CI 2.06-2.25, p < 0.0001). 2002 database contained a total of 7,853,982 patients. Diabetes occurred in (0.4 %) of patients with third-degree AV-block vs. (0.2 %) of the control (OR: 1.86, CI: 1.80-1.93, p < 0.0001). Using Multivariate analysis adjusting for age, congestive heart failure, and coronary artery disease, DM remained independently associated with third-degree AV block in both databases. (for 1999: OR: 2.54, CI 2.51-2.57, p < 0.0001 and for 2002 OR: 1.56, CI 1.55-1.57, p < 0.0001).

CONCLUSION

DM is independently associated with third-degree AV-block with persistent association over a period of 10 years. The cause of this association warrants further investigation.

Type 2 diabetes mellitus and higher rate of complete atrioventricular block: a Danish Nationwide Registry

AIMS

The present study aimed to determine the association between Type 2 diabetes mellitus (T2DM) and third-degree (complete) atrioventricular block.

METHODS AND RESULTS

This nationwide nested case-control study included patients older than 18 years, diagnosed with third-degree atrioventricular block between 1 July 1995 and 31 December 2018. Data on medication, comorbidity, and outcomes were collected from Danish registries. Five controls, from the risk set of each case of third-degree atrioventricular block, were matched on age and sex to fit a Cox regression model with time-dependent exposure and time-dependent covariates. Subgroup analysis was conducted with Cox regression models for each subgroup. We located 25 995 cases with third-degree atrioventricular block that were matched with 130 004 controls. The mean age was 76 years and 62% were male. Cases had more T2DM (21% vs. 11%), hypertension (69% vs. 50%), atrial fibrillation (25% vs. 10%), heart failure (20% vs. 6.3%), and myocardial infarction (19% vs. 9.2%), compared with the control group. In Cox regression analysis, adjusting for comorbidities and atrioventricular nodal blocking agents, T2DM was significantly associated with third-degree atrioventricular block (hazard ratio: 1.63, 95% confidence interval: 1.57-1.69). The association remained in several subgroup analyses of diseases also suspected to be associated with third-degree atrioventricular block. There was a significant interaction with comorbidities of interest including hypertension, atrial fibrillation, heart failure, and myocardial infarction.

CONCLUSION

In this nationwide study, T2DM was associated with a higher rate of third-degree atrioventricular block compared with matched controls. The association remained independent of atrioventricular nodal blocking agents and other comorbidities known to be associated with third-degree atrioventricular block.

Counterregulatory responses to postprandial hypoglycemia after Roux-en-Y gastric bypass

BACKGROUND

Postbariatric hypoglycemia (PBH) is a potentially serious complication after Roux-en-Y gastric bypass (RYGB), and impaired counterregulatory hormone responses have been suggested to contribute to the condition.

OBJECTIVES

We evaluated counterregulatory responses during postprandial hypoglycemia in individuals with PBH who underwent RYGB.

SETTING

University hospital.

METHODS

Eleven women with documented PBH who had RYGB underwent a baseline liquid mixed meal test (MMT) followed by 5 MMTs preceded by treatment with (1) acarbose 50 mg, (2) sitagliptin 100 mg, (3) verapamil 120 mg, (4) liraglutide 1.2 mg, and (5) pasireotide 300 μg. Blood was collected at fixed time intervals. Plasma and serum were analyzed for glucose, insulin, glucagon, epinephrine, norepinephrine, pancreatic polypeptide (PP), and cortisol.

RESULTS

During the baseline MMT, participants had nadir blood glucose concentrations of 3.3 ± .2 mmol/L. At the time of nadir glucose, there was a small but significant increase in plasma glucagon. Plasma epinephrine concentrations were not increased at nadir glucose but were significantly elevated by the end of the MMT. There were no changes in norepinephrine, PP, and cortisol concentrations in response to hypoglycemia. After treatment with sitagliptin, 8 individuals had glucose nadirs <3.2 mmol/L (versus 4 individuals at baseline), and significant increases in glucagon, PP, and cortisol responses were observed.

CONCLUSIONS

In response to postprandial hypoglycemia, individuals with PBH who underwent RYGB only had minor increases in counterregulatory hormones, while larger hormone responses occurred when glucose levels were lowered during treatment with sitagliptin. The glycemic threshold for counterregulatory activation could be altered in individuals with PBH, possibly explained by recurrent hypoglycemia.

Hypoglycaemia leads to a delayed increase in platelet and coagulation activation markers in people with type 2 diabetes treated with metformin only: Results from a stepwise hypoglycaemic clamp study

AIMS

To investigate the effect of hypoglycaemia on platelet and coagulation activation in people with type 2 diabetes.

MATERIALS AND METHODS

This monocentric, open, single-arm, mechanistic trial included 14 people with established type 2 diabetes (four women, 10 men, age 55 ± 7 years, glycated haemoglobin concentration 51 ± 7 mmol/mol) receiving metformin monotherapy. A stepwise hyperinsulinaemic-hypoglycaemic clamp experiment (3.5 and 2.5 mmol/L, for 30 minutes respectively) was performed, aiming to investigate platelet and coagulation activity during predefined plateaus of hypoglycaemia, as well as 1 day and 7 days later.

RESULTS

While platelet activation assessed by light transmittance aggregometry did not significantly increase after the hypoglycaemic clamp procedure, the more sensitive flow cytometry-based measurement of platelet surface activation markers showed hypoglycaemia-induced activation 24 hours (PAC1^pos CD62P^pos , PAC1^pos CD63P^pos and PAC1^pos CD62P^pos CD63^pos ; P < .01) and 7 days after the hypoglycaemic clamp (P < .001 for PAC1^pos CD63^pos ; P < .01 for PAC1^pos CD62P^pos and PAC1^pos CD62P^pos CD63^pos ) in comparison to baseline. Coagulation markers, such as fibrinogen, D-dimer, plasminogen activator inhibitor-1, von Willebrand factor activity and factor VIII, were also significantly increased, an effect that was most pronounced 24 hours after the hypoglycaemic clamp.

CONCLUSION

A single event of insulin-induced hypoglycaemia led to an increase in markers of platelet activation and coagulation in people with early stages of type 2 diabetes on metformin therapy. However, the activation occurred with a delay and was evident 24 hours and 7 days after the actual hypoglycaemic episode.

Diabetes and Arrhythmias: Pathophysiology, Mechanisms and Therapeutic Outcomes

The prevalence of diabetes is rapidly increasing and closely associated with cardiovascular morbidity and mortality. While the major cardiovascular complication associated with diabetes is coronary artery disease, it is becoming increasingly apparent that diabetes impacts the electrical conduction system in the heart, resulting in atrial fibrillation, and ventricular arrhythmias. The relationship between diabetes and arrhythmias is complex and multifactorial including autonomic dysfunction, atrial and ventricular remodeling and molecular alterations. This review will provide a comprehensive overview of the link between diabetes and arrhythmias with insight into the common molecular mechanisms, structural alterations and therapeutic outcomes.

Severe Hypoglycemia-Induced Fatal Cardiac Arrhythmias Are Augmented by Diabetes and Attenuated by Recurrent Hypoglycemia

We previously demonstrated that insulin-mediated severe hypoglycemia induces lethal cardiac arrhythmias. However, whether chronic diabetes and insulin deficiency exacerbates, and whether recurrent antecedent hypoglycemia ameliorates, susceptibility to arrhythmias remains unknown. Thus, adult Sprague-Dawley rats were randomized into four groups: 1) nondiabetic (NONDIAB), 2) streptozotocin-induced insulin deficiency (STZ), 3) STZ with antecedent recurrent (3 days) hypoglycemia (∼40-45 mg/dL, 90 min) (STZ+RH), and 4) insulin-treated STZ (STZ+Ins). Following treatment protocols, all rats underwent hyperinsulinemic (0.2 units ⋅ kg^-1 ⋅ min^-1), severe hypoglycemic (10-15 mg/dL) clamps for 3 h with continuous electrocardiographic recordings. During matched nadirs of severe hypoglycemia, rats in the STZ+RH group required a 1.7-fold higher glucose infusion rate than those in the STZ group, consistent with the blunted epinephrine response. Second-degree heart block was increased 12- and 6.8-fold in the STZ and STZ+Ins groups, respectively, compared with the NONDIAB group, yet this decreased 5.4-fold in the STZ+RH group compared with the STZ group. Incidence of third-degree heart block in the STZ+RH group was 5.6%, 7.8-fold less than the incidence in the STZ group (44%). Mortality due to severe hypoglycemia was 5% in the STZ+RH group, 6.2-fold less than that in the STZ group (31%). In summary, severe hypoglycemia-induced cardiac arrhythmias were increased by insulin deficiency and diabetes and reduced by antecedent recurrent hypoglycemia. In this model, recurrent moderate hypoglycemia reduced fatal severe hypoglycemia-induced cardiac arrhythmias.

Understanding the impact of hypoglycemia on the cardiovascular system

INTRODUCTION

Hypoglycemia occurs commonly in insulin requiring individuals with either Type 1 or Type 2 Diabetes.

AREAS COVERED

This article will review recent information on the pro-inflammatory and pro-atherothrombotic effects of hypoglycemia. Additionally, effects of hypoglycemia on arrhythmogenic potential and arterial endothelial dysfunction will be discussed. Effects of hypoglycemia on cardiovascular morbidity and mortality from large clinical studies in Type 1 and Type 2 DM will also be reviewed.

EXPERT COMMENTARY

The relative and absolute risk of severe hypoglycemia leading to death and serious adverse events in both cardiovascular and other organ systems has been highlighted following the publication of recent large clinical trials focused on glucose control and outcomes. It would be helpful if future studies could develop broader end points to include minor and moderate hypoglycemia as well as more robust methods for capturing hypoglycemia contemporaneously with adverse events. In addition, perhaps consideration of including hypoglycemia as a primary outcome, may help identify the possible cause and effect of hypoglycemia on cardiovascular morbidity and mortality.

Molecular and Electrophysiological Mechanisms Underlying Cardiac Arrhythmogenesis in Diabetes Mellitus

Diabetes is a common endocrine disorder with an ever increasing prevalence globally, placing significant burdens on our healthcare systems. It is associated with significant cardiovascular morbidities. One of the mechanisms by which it causes death is increasing the risk of cardiac arrhythmias. The aim of this article is to review the cardiac (ion channel abnormalities, electrophysiological and structural remodelling) and extracardiac factors (neural pathway remodelling) responsible for cardiac arrhythmogenesis in diabetes. It is concluded by an outline of molecular targets for future antiarrhythmic therapy for the diabetic population.

Blood electrolyte disturbances during severe hypoglycemia in Korean patients with type 2 diabetes

BACKGROUND/AIMS

To investigate abnormalities in blood electrolyte levels during severe hypoglycemia in Korean patients with type 2 diabetes mellitus (T2DM) in a clinical setting.

METHODS

Blood electrolyte levels in adult T2DM patients during severe hypoglycemia were collected from January 1, 2008 to December 31, 2012. Patients who maintained normal serum creatinine and blood urea nitrogen levels were utilized in the study. Severe hypoglycemia was defined as a condition requiring medical assistance, such as administering carbohydrates when serum glucose levels less than 70 mg/dL were observed, in conjunction with other symptoms of hypoglycemia.

RESULTS

A total of 1,068 patients who visited the emergency room with severe hypoglycemia were screened, of which 219 patients were included in this study. The incidence of abnormal levels for any electrolyte was 47%. Hypokalemia (< 3.5 mmol/L) was the most common type of electrolyte disturbance observed at 21.9%. A decrease in serum potassium levels was associated with decreases in blood glucose levels (r = 0.151, p = 0.025). During severe hypoglycemia, median blood glucose levels, incidence of tachycardia (> 100 beats per minute) and severe hypertension (≥ 180/120 mmHg) were 30 mg/dL (range, 14 to 62) and 35 mg/dL (range, 10 to 69; p = 0.04), 18.8% and 7.2% (p = 0.02), and 20.8% and 10.2% (p = 0.05) in the hypokalemia and normokalemia groups, respectively.

CONCLUSIONS

During severe hypoglycemia, hypokalemia occurred in 21.9% of T2DM patients and was associated with tachycardia and severe hypertension. Therefore, the results suggest that severe hypoglycemia may increase cardiovascular events in T2DM.

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.

Corrected QT Interval Prolongation during Severe Hypoglycemia without Hypokalemia in Patients with Type 2 Diabetes

BACKGROUND

To evaluate the effects of severe hypoglycemia without hypokalemia on the electrocardiogram in patients with type 2 diabetes in real-life conditions.

METHODS

Electrocardiograms of adult type 2 diabetic patients during the episodes of severe hypoglycemia and the recovered stage were obtained and analysed between October 1, 2011 and May 31, 2012. Patients who maintained the normal serum sodium and potassium levels during the episodes of severe hypoglycemia were only selected as the subjects of this study. Severe hypoglycemia was defined, in this study, as the condition requiring active medical assistance such as administering carbohydrate when serum glucose level was less than 60 mg/dL.

RESULTS

Nine type 2 diabetes patients (seven men, two women) were included in the study. The mean subject age was 73.2±7.7 years. The mean hemoglobin A1c level was 6.07%±1.19%. The median duration of diabetes was 10 years (range, 3.5 to 30 years). Corrected QT (QTc) intervals were significantly increased during the episodes of severe hypoglycemia compared to the recovered stage (447.6±18.2 ms vs. 417.2±30.6 ms; P<0.05). However, the morphology and the amplitude of the T waves were not changed and ST-segment elevation and/or depression were not found during the episodes of severe hypoglycemia.

CONCLUSION

In this study, QTc interval prolongation during the episodes of severe hypoglycemia was observed without hypokalemia. Therefore, the distinct alterations in cardiac repolarization during the episodes of severe hypoglycemia may not be associated with hypokalemia.

Hypoglycemia revisited in the acute care setting

Hypoglycemia is a common finding in both daily clinical practice and acute care settings. The causes of severe hypoglycemia (SH) are multi-factorial and the major etiologies are iatrogenic, infectious diseases with sepsis and tumor or autoimmune diseases. With the advent of aggressive lowering of HbA1c values to achieve optimal glycemic control, patients are at increased risk of hypoglycemic episodes. Iatrogenic hypoglycemia can cause recurrent morbidity, sometime irreversible neurologic complications and even death, and further preclude maintenance of euglycemia over a lifetime of diabetes. Recent studies have shown that hypoglycemia is associated with adverse outcomes in many acute illnesses. In addition, hypoglycemia is associated with increased mortality among elderly and non-diabetic hospitalized patients. Clinicians should have high clinical suspicion of subtle symptoms of hypoglycemia and provide prompt treatment. Clinicians should know that hypoglycemia is associated with considerable adverse outcomes in many acute critical illnesses. In order to reduce hypoglycemia-associated morbidity and mortality, timely health education programs and close monitoring should be applied to those diabetic patients presenting to the Emergency Department with SH. ED disposition strategies should be further validated and justified to achieve balance between the benefits of euglycemia and the risks of SH. We discuss relevant issues regarding hypoglycemia in emergency and critical care settings.

Dynamics of blood electrolytes in repeated hyper- and/or hypoglycaemic events in patients with type 1 diabetes

AIMS/HYPOTHESIS

Electrolyte disturbances are well-known consequences of the diabetic pathology. However, less is known about the cumulative effects of repeated changes in glycaemia, a characteristic of diabetes, on the electrolyte balance. We therefore investigated the ionic profiles of patients with type 1 diabetes during consecutive hyper- and/or hypoglycaemic events using the glucose clamp.

METHODS

In protocol 1, two successive hyperglycaemic excursions to 18 mmol/l were induced; in protocol 2, a hypoglycaemic excursion (2.5 mmol/l) was followed by a hyperglycaemic excursion (12 mmol/l) and another hypoglycaemic episode (3.0 mmol/l).

RESULTS

Blood osmolarity increased during hyperglycaemia and was unaffected by hypoglycaemia. Hyperglycaemia induced decreases in plasma Na(+) Cl(-) and Ca(2+) concentrations and increases in K(+) concentrations. These changes were faithfully reproduced during a second hyperglycaemia. Hypoglycaemia provoked rapid and rapidly reversible increases in Na(+), Cl(-) and Ca(2+). In sharp contrast, K(+) levels displayed a rapid and substantial fall from which they did not fully recover even 2 h after the re-establishment of euglycaemia. A second hypoglycaemia caused an additional fall.

CONCLUSIONS/INTERPRETATION

Repeated hyperglycaemia events do not lead to any cumulative effects on blood electrolytes. However, repeated hypoglycaemias are cumulative with respect to K(+) levels due to a very slow recovery following hypoglycaemia. These results suggest that recurring hypoglycaemic events may lead to progressively lower K(+) levels despite rapid re-establishment of euglycaemia. This warrants close monitoring of plasma K(+) levels combined with continuous glucose monitoring particularly in patients under intensive insulin therapy who are subject to repeated hypoglycaemic episodes.

TRIAL REGISTRATION

Clinicaltrial.gov NCT01060917.

A physiological model of the effect of hypoglycemia on plasma potassium

BACKGROUND

Adrenaline release and excess insulin during hypoglycemia stimulate the uptake of potassium from the bloodstream, causing low plasma potassium (hypokalemia). Hypokalemia has a profound effect on the heart and is associated with an increased risk of malignant cardiac arrhythmias. It is the aim of this study to develop a physiological model of potassium changes during hypoglycemia to better understand the effect of hypoglycemia on plasma potassium.

METHOD

Potassium counterregulation to hypokalemia was modeled as a linear function dependent on the absolute potassium level. An insulin-induced uptake of potassium was modeled using a negative exponential function, and an adrenaline-induced uptake of potassium was modeled as a linear function. Functional expressions for the three components were found using published data.

RESULTS

The performance of the model was evaluated by simulating plasma potassium from three published studies. Simulations were done using measured levels of adrenaline and insulin. The mean root mean squared error (RMSE) of simulating plasma potassium from the three studies was 0.09 mmol/liter, and the mean normalized RMSE was 14%. The mean difference between nadirs in simulated and measured potassium was 0.12 mmol/liter.

CONCLUSIONS

The presented model simulated plasma potassium with good accuracy in a wide range of clinical settings. The limited number of hypoglycemic episodes in the test set necessitates further tests to substantiate the ability of the model to simulate potassium during hypoglycemia. In conclusion, the model is a good first step toward better understanding of changes in plasma potassium during hypoglycemia.

Effects of a controlled hypoglycaemia test on QTc in adolescents with Type 1 diabetes

Our objective was to test the ventricular repolarization response to a controlled hypoglycaemia test in Type 1 diabetic adolescents, an age group at risk for 'dead in bed syndrome'. We measured QTc, blood glucose level, potassium, heart rate, blood pressure and urinary metanephrine levels in 16 Type 1 diabetic adolescents during an insulin clamp mimicking the transition from mild hyperglycaemia to hypoglycaemia. QTc increased in all patients by 146 +/- 44 ms (mean +/-sd) ranging from 70 to 230 ms. The longest QTc (630 ms) was recorded in the sibling of a diabetic patient found 'dead in bed'. Heart rate and urinary metanephrine levels correlated with QTc (r = 0.60 and 0.79, respectively; P = 0.02 and 0.003). QTc in euglycaemia showed no correlation with hypoglycaemia associated QTc prolongation. The prognostic value of the hypoglycaemia test for the risk of recurrent episodes of QTc prolongation should be evaluated in real-life conditions in large-scale studies of diabetic adolescents.

Effects of carbenoxolone on heart rhythm, contractility and intracellular calcium in streptozotocin-induced diabetic rat

Cardiac dysfunction is a frequently reported complication of clinical and experimental diabetes mellitus. Streptozotocin (STZ)-induced diabetes in rat is associated with a variety of cardiac defects including disturbances to heart rhythm and prolonged time-course of cardiac muscle contraction and/or relaxation. The effects of carbenoxolone (CBX), a selective gap junction inhibitor, on heart rhythm and contractility in STZ-induced diabetic rat have been investigated. Heart rate was significantly (P < 0.05) reduced in Langendorff perfused spontaneously beating diabetic rat heart (171+/-12 BPM) compared to age-matched controls (229+/- 9 BPM) and further reduced by 10(-5) M CBX in diabetic (20%) and in control (17%) hearts. Action potential durations (APDs), recorded on the epicardial surface of the left ventricle, were prolonged in paced (6 Hz) diabetic compared to control hearts. Perfusion of hearts with CBX caused further prolongation of APDs and to a greater extent in control compared to diabetic heart. Percentage prolongation at 70% from the peak of the action potential amplitude after CBX was 18% in diabetic compared to 48% in control heart. CBX had no significant effect on resting cell length or amplitude of ventricular myocyte shortening in diabetic or control rats. However, resting fura-2 ratio (indicator for intracellular Ca(2+) concentration) and amplitude of the Ca(2+) transient were significantly (P < 0.05) reduced by CBX in diabetic rats but not in controls. In conclusion the larger effects of CBX on APD in control ventricle and the normalizing effects of CBX on intracellular Ca(2+) in ventricular myocytes from diabetic rat suggest that there may be alterations in gap junction electrophysiology in STZ-induced diabetic rat heart.