Relationship between abnormal microvolt T-wave alternans and poor glycemic control in type 2 diabetic patients

Dysglycemia and arrhythmias

Disorders in glucose metabolism can be divided into three separate but interrelated domains, namely hyperglycemia, hypoglycemia, and glycemic variability. Intensive glycemic control in patients with diabetes might increase the risk of hypoglycemic incidents and glucose fluctuations. These three dysglycemic states occur not only amongst patients with diabetes, but are frequently present in other clinical settings, such as during critically ill. A growing body of evidence has focused on the relationships between these dysglycemic domains with cardiac arrhythmias, including supraventricular arrhythmias (primarily atrial fibrillation), ventricular arrhythmias (malignant ventricular arrhythmias and QT interval prolongation), and bradyarrhythmias (bradycardia and heart block). Different mechanisms by which these dysglycemic states might provoke cardiac arr-hythmias have been identified in experimental studies. A customized glycemic control strategy to minimize the risk of hyperglycemia, hypoglycemia and glucose variability is of the utmost importance in order to mitigate the risk of cardiac arrhythmias.

Empagliflozin attenuates arrhythmogenesis in diabetic cardiomyopathy by normalizing intracellular Ca2+ handling in ventricular cardiomyocytes

Diabetic cardiomyopathy has been reported to increase the risk of fatal ventricular arrhythmia. The beneficial effects of the selective sodium-glucose cotransporter-2 inhibitor have not been fully examined in the context of antiarrhythmic therapy, especially its direct cardioprotective effects despite the negligible SGLT2 expression in cardiomyocytes. We aimed to examine the antiarrhythmic effects of empagliflozin (EMPA) treatment on diabetic cardiomyocytes, with a special focus on Ca²⁺ handling. We conducted echocardiography and hemodynamic studies and studied electrophysiology, Ca²⁺ handling, and protein expression in C57BLKS/J-lepr^db/db mice (db/db mice) and their nondiabetic lean heterozygous Lepr^db/+ littermates (db/⁺ mice). Preserved systolic function with diastolic dysfunction was observed in 16-wk-old db/db mice. During arrhythmia induction, db/db mice had significantly increased premature ventricular complexes (PVCs) than controls, which was attenuated by EMPA. In protein expression analyses, calmodulin-dependent protein kinase II (CaMKII) Thr287 autophosphorylation and CaMKII-dependent RyR2 phosphorylation (S2814) were significantly increased in diabetic hearts, which were inhibited by EMPA. In addition, global O-GlcNAcylation significantly decreased with EMPA treatment. Furthermore, EMPA significantly inhibited ventricular cardiomyocyte glucose uptake. Diabetic cardiomyocytes exhibited increased spontaneous Ca²⁺ events and decreased sarcoplasmic reticulum (SR) Ca²⁺ content, along with impaired Ca²⁺ transient, all of which normalized with EMPA treatment. Notably, most EMPA-induced improvements in Ca²⁺ handling were abolished by the addition of an O-GlcNAcase (OGA) inhibitor. In conclusion, EMPA attenuated ventricular arrhythmia inducibility by normalizing the intracellular Ca²⁺ handling, and we speculated that this effect was, at least partly, due to the inhibition of O-GlcNAcylation via the suppression of glucose uptake into cardiomyocytes.NEW & NOTEWORTHY SGLT2is are known to improve cardiovascular outcomes regardless of the presence of diabetes and decrease traditional cardiovascular risk factors. We demonstrated, for the first time, that EMPA inhibited PVCs by normalizing Ca²⁺ handling in diabetic mice. Our data suggest that the effects of SGLT2is on calcium handling may occur because of suppression of O-GlcNAcylation through inhibition of glucose uptake and not because of NHE inhibition, as previously suggested.

Impact of sodium-glucose co-transporter inhibitors on cardiac autonomic function and mortality: no time to die

Sodium-glucose co-transporter 2 (SGLT2) inhibitors have been shown to improve cardiovascular outcomes not only in patients with diabetes but also in those with heart failure, irrespective of diabetic status. However, the mechanisms underlying the cardioprotective effects of these newer anti-diabetic drugs remain to be fully elucidated. One exciting avenue that has been recently explored in both preclinical and clinical studies is the modulation of the cardiovascular autonomic nervous system. A reduction in sympathetic nervous system activity by SGLT2 inhibitors may potentially translate into a reduction in arrhythmic risk and sudden arrhythmic death, which may explain, at least partly, the cardioprotection shown in the cardiovascular outcome trials with different SGLT2 inhibitors. Although some of the data from the preclinical and clinical studies are promising, overall the findings can be contradictory. This highlights the need for more studies to address gaps in our knowledge of these novel drugs. The present review offers an in depth overview of the existing literature regarding the role of SGLT2 inhibitors in modulating cardiovascular autonomic function as one of the possible pathways of their cardioprotective effects.

Does a strict glycemic control during acute coronary syndrome play a cardioprotective effect? Pathophysiology and clinical evidence

A hyperglycemic state, also in non-diabetic subjects, may be associated with acute coronary syndrome (ACS). Aim of this review is to describe the pathophysiologic association between ACS and hyperglycemic state, the protective mechanisms of a tight glycaemic control in ACS on CV outcomes, and the supporting clinical evidence. Several mechanisms may be responsible of a poor CV outcome in subjects with hyperglycemia during ACS. Endothelial NAPDH oxidase-2 (NOX2) activation in response to high glucose alters the balance between Raf/MAPK-dependent vasoconstriction and PI3K/Akt-dependent vasodilation in favour of constriction. Hyperglycaemia induces an overproduction of superoxide by the mitochondrial electron transport chain through different molecular mechanisms. Moreover, hyperglycaemia increases the size of the infarct by causing myocardial cell death through apoptosis and reducing the collateral blood flow. High FFA concentrations lead to toxicity mechanisms in acutely ischemic myocardium. On the other hand, a tight glycaemic control in ACS exerts a cardioprotective action by anti-inflammatory and anti-apoptotic mechanisms, anti-oxidative stress, endothelium protection, FFA reduction, anti-glucotoxic effect, IR and cardiac fuel metabolisms improvement, heart stem cells protection and reduced activation of adrenergic system. Unfortunately, the clinical studies supporting the above pathophysiological background are few and sometimes controversial, more likely due the risk of hypoglycemia linked to the insulin therapy generally used during ACS. Intriguingly, GLP-1 RA and SGLT2i, demonstrated highly effective in the cardiovascular prevention in high-risk subjects without the risk of hypoglycemia, might keep this cardioprotective effect even in acute conditions such as ASC.

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

AIM

We examined the effect of spontaneous hyperglycaemia in adults with type 1 diabetes mellitus (T1DM) and without history of cardiovascular disease on heart rate variability (HRV), cardiac repolarisation and incidence of cardiac arrhythmias.

METHODS

Thirty-seven individuals with T1DM (age 17-50 years, 19 males, mean duration of diabetes 19.3 SD(9.6) years) underwent 96 h of simultaneous ambulatory 12-lead Holter ECG and blinded continuous interstitial glucose (IG) monitoring (CGM). HRV, QT interval and cardiac repolarisation were assessed during hyperglycaemia (IG ≥ 15 mmol/l) and compared with matched euglycaemia (IG 5-10 mmol/l) on a different day, separately during the day and night. Rates of arrhythmias were assessed by calculating incidence rate differences.

RESULTS

Simultaneous ECG and CGM data were recorded for 2395 hours. During daytime hyperglycaemia vs euglycaemia the mean QT_c interval duration was 404 SD(21)ms vs 407 SD(20)ms, P = 0.263. T-peak to T-end interval duration corrected for heart rate (T_pT_endc) shortened: 74.8 SD(16.1)ms vs 79.0 SD(14.8)ms, P = 0.033 and T-wave symmetry increased: 1.62 SD(0.33) vs 1.50 SD(0.39), P = 0.02. During night-time hyperglycaemia vs euglycaemia, the mean QT_c interval duration was 401 SD(26)ms vs 404 SD(27)ms, P = 0.13 and T_pT_end shortened: 62.4 SD(12.0)ms vs 67.1 SD(11.8)ms, P = 0.003. The number of cardiac arrhythmias was low and confined to bradycardia and isolated ectopic beats. A considerable inter-subject and diurnal variability was observed.

CONCLUSIONS

Hyperglycaemia in individuals with T1DM without known cardiovascular disease was not associated with clinically important cardiac arrhythmias.

Diabetes and Its Complications: Therapies Available, Anticipated and Aspired

Worldwide, diabetes ranks among the ten leading causes of mortality. Prevalence of diabetes is growing rapidly in low and middle income countries. It is a progressive disease leading to serious co-morbidities, which results in increased cost of treatment and over-all health system of the country. Pathophysiological alterations in Type 2 Diabetes (T2D) progressed from a simple disturbance in the functioning of the pancreas to triumvirate to ominous octet to egregious eleven to dirty dozen model. Due to complex interplay of multiple hormones in T2D, there may be multifaceted approach in its management. The 'long-term secondary complications' in uncontrolled diabetes may affect almost every organ of the body, and finally may lead to multi-organ dysfunction. Available therapies are inconsistent in maintaining long term glycemic control and their long term use may be associated with adverse effects. There is need for newer drugs, not only for glycemic control but also for prevention or mitigation of secondary microvascular and macrovascular complications. Increased knowledge of the pathophysiology of diabetes has contributed to the development of novel treatments. Several new agents like Glucagon Like Peptide - 1 (GLP-1) agonists, Dipeptidyl Peptidase IV (DPP-4) inhibitors, amylin analogues, Sodium-Glucose transport -2 (SGLT- 2) inhibitors and dual Peroxisome Proliferator-Activated Receptor (PPAR) agonists are available or will be available soon, thus extending the range of therapy for T2D, thereby preventing its long term complications. The article discusses the pathophysiology of diabetes along with its comorbidities, with a focus on existing and novel upcoming antidiabetic drugs which are under investigation. It also dives deep to deliberate upon the novel therapies that are in various stages of development. Adding new options with new mechanisms of action to the treatment armamentarium of diabetes may eventually help improve outcomes and reduce its economic burden.

Effect of Intensive Glycemic and Blood Pressure Control on QT Prolongation in Diabetes: The ACCORD Trial

Compared with standard glycemic control, intensive glycemic control caused increased mortality in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Preliminary data from several studies suggest that intensive glycemic control is associated with QT prolongation, which may lead to ventricular arrhythmias as a possible explanation of this increased mortality. We sought to assess the effects of intensive glycemic control and intensive blood pressure control on the risk of incident QT prolongation. Cox proportional hazards models were used to compare the risk of incident QT prolongation (>460 ms in women or >450 ms in men) in the intensive versus standard glycemic control arms. Over a combined 48,634 person-years of follow-up (mean 4.9), 634 participants (6.4%) developed a prolonged QTc. Participants in the intensive glycemic control arm did not have an increased risk of QT prolongation. Similarly, a strategy of intensive blood pressure control did not result in a significant change in risk of prolonged QTc. Sensitivity analyses using alternative QT correction formulas (Hodges and Bazett) yielded overall similar findings. In conclusion, the increased mortality observed in the intensive glycemic control arm in the ACCORD trial is not likely to be explained by QT prolongation leading to lethal ventricular arrhythmias.

The association between SGLT2 inhibitors and new-onset arrhythmias: a nationwide population-based longitudinal cohort study

Background

Clinical trials have shown the cardiovascular protective effect of sodium–glucose cotransporter-2 (SGLT2) inhibitors and reduced hospitalization for heart failure. However, no study has investigated the association between SGLT2 inhibitors and the risk of arrhythmias. This study aimed to evaluate the risk of new-onset arrhythmias (NOA) and all-cause mortality with the use of SGLT2 inhibitors.

Methods

This was a population-based cohort study utilizing Taiwan’s National Health Insurance Research Database. Each patient aged 20 years and older who took SGLT2 inhibitors was assigned to the SGLT2 inhibitor group, whereas sex-, age-, diabetes mellitus duration-, drug index date-, and propensity score-matched randomly selected patients without SGLT2 inhibitors were assigned to the non-SGLT2 inhibitor group. The study outcome was all-cause mortality and NOA.

Results

A total of 399,810 patients newly diagnosed with type 2 DM were enrolled. A 1:1 matching propensity method was used to match 79,150 patients to 79,150 controls in the non-SGLT2 inhibitors group for analysis. The SGLT2 inhibitor group was associated with a lower risk of all-cause mortality [adjusted hazard ratio (aHR) 0.547; 95% confidence interval (CI) 0.482–0.621; P = 0.0001] and NOA (aHR 0.830; 95% CI 0.751–0.916; P = 0.0002).

Conclusions

Patients with type 2 DM prescribed with SGLT2 inhibitors were associated with a lower risk of all-cause mortality and NOA compared with those not taking SGLT2 inhibitors in real-world practice.

Tips for management of arrhythmias in endocrine disorders from an European Heart Rhythm Association position paper

In endocrine diseases, hormonal changes, electrolyte abnormalities, and the deterioration of heart structure can lead to various arrhythmias. In diabetic patients, hypoglycemia, hyperglycemia, and hypokalemia can trigger arrhythmias, and diabetic cardiomyopathy can also cause electrical and structural remodeling to form substrates for arrhythmias. The risk of atrial fibrillation (AF) increases in hyperthyroidism; however, the prevalence of ventricular arrhythmias in hypothyroidism is higher. Besides AF and ventricular tachycardias, bradycardias and atrioventricular blocks can also be seen in pheochromocytoma due to the desensitization of adrenergic cardiovascular receptors. The correction of metabolic and electrolyte disturbances in patients with adrenal cortex disease should be the main approach in the prevention and treatment of arrhythmias. Early initiation of treatment in patients with acromegaly seems to decrease the development of cardiac remodeling and ventricular arrhythmia. Early and late after depolarizations due to hypercalcemia in hyperparathyroidism can lead to life-threatening ventricular arrhythmias. This elegant position paper provides important recommendations regarding prevention and treatment of arrhythmias for specific endocrine disorders.

Lower sarcoplasmic reticulum Ca2+ threshold for triggering afterdepolarizations in diabetic rat hearts

BACKGROUND

Type 2 diabetes (T2D) increases arrhythmia risk through incompletely elucidated mechanisms. Ventricular arrhythmias could be initiated by delayed afterdepolarizations (DADs) resulting from elevated spontaneous sarcoplasmic reticulum (SR) Ca2+ release (SR Ca2+ leak).

OBJECTIVE

The purpose of this study was to test the role of DADs and SR Ca2+ leak in triggering arrhythmias in T2D hearts.

METHODS

We compared rats with late-onset T2D that display pancreatic and cardiac phenotypes similar to those in humans with T2D (HIP rats) and their nondiabetic littermates (wild type [WT]).

RESULTS

HIP rats showed higher propensity for premature ventricular complexes and ventricular tachyarrhythmias, whereas HIP myocytes displayed more frequent DADs and had lower SR Ca2+ content than WT. However, the threshold SR Ca2+ at which depolarizing transient inward currents (Itis) are generated was also significantly decreased in HIP myocytes and was below the actual SR Ca2+ load, which explains the increased DAD incidence despite reduced Ca2+ in SR. In agreement with these findings, Ca2+ spark frequency was augmented in myocytes from HIP vs WT rats, which suggests activation of ryanodine receptors (RyRs) in HIP hearts. Indeed, RyR phosphorylation (by CaMKII and protein kinase A) and oxidation are enhanced in HIP hearts, whereas there is no RyR O-GlcNAcylation in either HIP or control hearts. CaMKII inhibition dissipated the difference in Ca2+ spark frequency between HIP and WT myocytes.

CONCLUSION

The threshold SR Ca2+ for generating depolarizing Itis is lower in T2D because of RyR activation after hyperphosphorylation and oxidation, which favors the occurrence of DADs despite low SR Ca2+ loads.

Heart rate variability in type 2 diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Cardiac autonomic neuropathy in type 2 dibetes mellitus (T2DM) patients is frequent and associated with high cardiovascular mortality. Heart rate variability (HRV) is the gold standard to measure cardiac autonomic neuropathy. We aimed to conduct a systematic review and meta-analysis to evaluate the impact of T2DM on HRV parameters.

METHODS

The PubMed, Cochrane Library, Embase and Science Direct databases were searched on 1st October 2017 using the keywords "diabetes" AND ("heart rate variability" OR "HRV"). Included articles had to report HRV parameters in T2DM patients and healthy controls measured during 24 hours with a Holter-electrocardiogram. Measurements of HRV retieved were: RR-intervals (or Normal to Normal intervals-NN), standard deviation of RR intervals (SDNN), percetange of adjacent NN intervals differing by more than 50 milliseconds (pNN50), square root of the mean squared difference of successive RR intervals (RMSSD), total power, Low Frequency (LF), High Frequency (HF) and LF/HF ratio, as per Task Force recommendations.

RESULTS

We included twenty-five case-control studies with 2,932 patients: 1,356 with T2DM and 1,576 healthy controls. T2DM patients had significantly (P<0.01) lower RR-intervals (effect size = -0.61; 95%CI -1.21 to -0.01), lower SDNN (-0.65; -0.83 to -0.47), lower RMSSD (-0.92; -1.37 to -0.47), lower pNN50 (-0.46; -0.84 to -0.09), lower total power (-1.52; -2.13 to -0.91), lower LF (-1.08; -1.46 to -0.69]), and lower HF (-0.79; -1.09 to -0.50). LF/HF did not differ between groups. Levels of blood glucose and HbA1c were associated with several HRV parameters, as well as Time from diagnosis of T2DM.

CONCLUSIONS

T2DM was associated with an overall decrease in the HRV of T2DM patients. Both sympathetic and parasympathetic activity were decreased, which can be explained by the deleterious effects of altered glucose metabolism on HRV, leading to cardiac autonomic neuropathy.

Data analytics identify glycated haemoglobin co-markers for type 2 diabetes mellitus diagnosis

Glycated haemoglobin (HbA1c) is being more commonly used as an alternative test for the identification of type 2 diabetes mellitus (T2DM) or to add to fasting blood glucose level and oral glucose tolerance test results, because it is easily obtained using point-of-care technology and represents long-term blood sugar levels. HbA1c cut-off values of 6.5% or above have been recommended for clinical use based on the presence of diabetic comorbidities from population studies. However, outcomes of large trials with a HbA1c of 6.5% as a cut-off have been inconsistent for a diagnosis of T2DM. This suggests that a HbA1c cut-off of 6.5% as a single marker may not be sensitive enough or be too simple and miss individuals at risk or with already overt, undiagnosed diabetes. In this study, data mining algorithms have been applied on a large clinical dataset to identify an optimal cut-off value for HbA1c and to identify whether additional biomarkers can be used together with HbA1c to enhance diagnostic accuracy of T2DM. T2DM classification accuracy increased if 8-hydroxy-2-deoxyguanosine (8-OhdG), an oxidative stress marker, was included in the algorithm from 78.71% for HbA1c at 6.5% to 86.64%. A similar result was obtained when interleukin-6 (IL-6) was included (accuracy=85.63%) but with a lower optimal HbA1c range between 5.73 and 6.22%. The application of data analytics to medical records from the Diabetes Screening programme demonstrates that data analytics, combined with large clinical datasets can be used to identify clinically appropriate cut-off values and identify novel biomarkers that when included improve the accuracy of T2DM diagnosis even when HbA1c levels are below or equal to the current cut-off of 6.5%.

Role of diabetes in heart rhythm disorders

The incidence of diabetes mellitus (DM) is increasing rapidly. DM is the leading cause of cardiovascular diseases, which can lead to varied cardiovascular complications by aggravated atherosclerosis in large arteries and coronary atherosclerosis, thereby grows the risk for macro and microangiopathy such as myocardial infarction, stroke, limb loss and retinopathy. Moreover diabetes is one of the strongest and independent risk factor for cardiovascular morbidity and mortality, which associated frequently rhythm disorders such as atrial fibrillation (AF) and ventricular arrhythmias (VA). The present article provides a concise overview of the association between DM and rhythm disorders such as AF and VA with underlying pathophysiological mechanisms.

High signal intensity on T2-weighted cardiac magnetic resonance imaging correlates with the ventricular tachyarrhythmia in hypertrophic cardiomyopathy

Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) can predict ventricular arrhythmia and poor prognosis in hypertrophic cardiomyopathy (HCM) patients. Although myocardial T2-high signal has been reported to appear within LGE in those patients, its clinical significance remains unclear. We investigated the relationship between the T2-high signal and nonsustained ventricular tachycardia (NSVT) in HCM patients. Eighty-one HCM patients who underwent Holter ECG and CMR including T2-weighted and LGE imaging were retrospectively recruited. They were divided into NSVT-positive and NSVT-negative groups. We compared the clinical and CMR characteristics between both of the groups, and assessed predictors of NSVT with multivariate analysis. Myocardial T2-high signal was observed in 15/81 (18.5 %) patients. Each T2-high signal was localized within LGE. Significantly in the NSVT-positive group, the prevalence of atrial fibrillation [5/17 (29.4 %) vs. 2/64 (3.1 %), p = 0.0006] and T2-high signal [9/17 (52.9 %) vs. 6/64 (9.4 %), p < 0.0001] and the left ventricular (LV) end-systolic volume index (32.2 ± 15.9 ml/m(2) vs. 23.3 ± 14.9 ml/m(2), p = 0.034) and the number of segments with LGE (5.8 ± 3.3 vs. 2.7 ± 2.7, p < 0.0001) was increased, and the LV ejection fraction (54.8 ± 10.9 % vs. 65.1 ± 10.6 %, p = 0.0007) was decreased, compared to the NSVT-negative group. On multivariate analysis, the presence of atrial fibrillation (OR 29.49, p = 0.0025) and DM (OR 7.36, p = 0.0455) and T2-high signal (OR 14.96, p = 0.0014) and reduced LV ejection fraction (OR 0.93, p = 0.0222) were significantly associated with NSVT. The presence of myocardial T2-high signal is a significant independent predictor of NSVT in HCM patients.

[Impairment of cardiac autonomic nervous system and incidence of arrhythmias in severe hyperglycemia]

BACKGROUND AND PURPOSE

Deterioration of cardiac autonomic nervous system in diabetics is associated with increased cardiac and arrhythmogenic mortality. Therefore, the present study engaged in the question how heart rate variability is acutely changed in diabetic ketoacidosis or hyperglycemic hyperosmolar syndrome. Moreover was evaluated how blood pressure, heart rate and incidence of arrhythmias can be explained by figures of heart rate variability.

PATIENTS AND METHODS

In a prospective observation of time course we investigated in 4 years consecutively 12 intensive care patients with DKA and 2 with HHS (10 male, 4 female, 19-62 years, initial plasma glucose 404-1192 mg/dl). All patients received a standardized treatment to international current guidelines. In addition to hemodynamic and clinical-chemical monitoring HRV analysis was performed continuously for at least 48 hours. Simultaneously, we determined supraventricular and ventricular arrhythmic episodes.

RESULTS

HRV was diminished over the whole spectrum in dependence on blood glucose concentration. Thus, sympathovagal balance (LF/HF ratio) was initially sympathetic predominated in blood glucose levels < 600 mg/dl (relatively prevailing LF power) and vagal predominated in blood glucose levels > 600 mg/dl (relatively prevailing HF power). In correlation analysis of HRV parameters with blood glucose rS-coefficients from -0.934 to -0.821 were achieved (p < 0.001). Further, the initial mean blood pressure correlated with the LF/HF ratio in HRV minimum (rS = 0.711, p = 0.004). The initial heart rate in relation to assumed intrinsic frequency correlated with minimal found Total Power (rS = -0.656, p = 0.011). In the period of whole 48 hours, more arrhythmic events occurred in consequence to initial glucose levels (rS = 0.693, p = 0.006). But the maximum of arrhythmic episodes was usually later ascertained than the minimum of HRV (p < 0.001). At the time of each arrhythmic maximum the sympathovagal balance (LF/HF) showed no uniform figures. Only similar in all cases was that the LF/HF ratio was found either > 4 or < 1.

CONCLUSION

Clinical complications in high glucose levels must be seen in the context of a nearly complete blockade of sympathetic and parasympathetic activity. Basically to extreme autonomic restriction, sympathetic and vagal predominance can change rapidly into each other. This retarded vulnerable predisposition may declare the arrhythmic potential. An important progress in the monitoring of patients could be achieved by implementation of a continuous HRV measurement because hereby the actual risk potential can be ascertained timely and reliably.

Torsade de pointes in a patient with acute prolonged QT syndrome and poorly controlled diabetes during sevoflurane anaesthesia

We report a case of torsade de pointes secondary to acute QT interval prolongation in a patient with poorly controlled diabetes mellitus towards the end of a laparoscopic nephrectomy under sevoflurane anaesthesia. The patient was successfully resuscitated and made a complete recovery. Our case suggests that acute QT interval prolongation should be considered in any patient with poor glycaemic control during prolonged procedures.

Glycemic control and cardiovascular events in diabetic hemodialysis patients

BACKGROUND

Patients on maintenance dialysis treatment experience an excess mortality, predominantly of sudden cardiac death. Poor glycemic control is associated with cardiovascular comorbidities in the general population. This study investigated the impact of glycemic control on cardiac and vascular outcomes in diabetic hemodialysis patients.

METHODS AND RESULTS

Glycohemoglobin A1c (HbA(1c)) was measured in 1255 hemodialysis patients with type 2 diabetes mellitus who participated in the German Diabetes and Dialysis Study (4D Study) and were followed up for a median of 4 years. Using Cox regression analyses, we determined hazard ratios to reach prespecified, adjudicated end points according to HbA(1c) levels at baseline: sudden cardiac death (n=160), myocardial infarction (n=200), stroke (n=103), cardiovascular events (n=469), death caused by heart failure (n=41), and all-cause mortality (n=617). Patients had a mean age of 66+/-8 years (54% male) and mean HbA(1c) of 6.7+/-1.3%. Patients with an HbA(1c) >8% had a >2-fold higher risk of sudden death compared with those with an HbA(1c) < or =6% (hazard ratio, 2.14; 95% confidence interval, 1.33 to 3.44), persisting in multivariate models. With each 1% increase in HbA(1c), the risk of sudden death rose significantly by 18%; similarly, cardiovascular events and mortality increased by 8%. There was a trend for higher risks of stroke and deaths resulting from heart failure, whereas myocardial infarction was not affected. The increased risks of both cardiovascular events and mortality were explained mainly by the impact of HbA(1c) on sudden death.

CONCLUSIONS

Poor glycemic control was strongly associated with sudden cardiac death in diabetic hemodialysis patients, which accounted for increased cardiovascular events and mortality. In contrast, myocardial infarction was not affected. Whether interventions achieving tight glycemic control decrease sudden death requires further evaluation. Clinical Trial Registration- URL: http://www.clinicalstudyresults.org. Unique identifier: CT-981-423-239.

Atrial fibrillation in patients with implantable defibrillators

Atrial fibrillation (AF) is common in patients who have implantable defibrillators and presents some unique challenges and opportunities. AF burden can be assessed more accurately, allowing for evaluation of therapy efficacy (drugs or ablation). It remains to be shown whether home monitoring of defibrillators to detect and treat AF more quickly can reduce cardiovascular and stroke end points. One major goal will be to reduce inappropriate shocks from atrial fibrillation. Otherwise, the goals of therapy remain the same-reduction of symptoms (including heart failure exacerbation and inappropriate implantable cardioverter defibrillator therapies) by controlling rate or rhythm and anticoagulation for stroke prophylaxis.

Sudden cardiac death: prevalence, pathogenesis, and prevention

Sudden cardiac death (SCD), also known as sudden arrest, is a major health problem worldwide. It is usually defined as an unexpected death from a cardiac cause occurring within a short time in a person with or without preexisting heart disease. The pathogenesis of SCD is complex and multifaceted. A dynamic triggering factor usually interacts with an underlying heart disease, either genetically determined or acquired, and the final outcome is the development of lethal tachyarrhythmias or, less frequently, bradycardia. It has increasingly been highlighted that a reliable clinical and diagnostic approach might be effective to unmask the most important genetic and environmental factors, allowing the construction of a rational personalized medicine framework that can be applied in both the preclinical and clinical settings of SCD. The aim of the present article is to provide a concise overview of prevalence, pathogenesis, clinical presentation, and diagnostic approach to this challenging disorder.

Relationship Between Abnormal Microvolt T-Wave Alternans and Poor Glycemic Control in Type 2 Diabetic Patients

BACKGROUND

Abnormal microvolt T-wave alternans (TWA) predicts the risk of ventricular arrhythmias and sudden cardiac death. Although type 2 diabetes is associated with an increased risk of these events, there is a dearth of available data on microvolt TWA measurements in type 2 diabetic populations.

METHODS

We studied 59 consecutive type 2 diabetic outpatients without manifest cardiovascular disease (CVD) and 35 non-diabetic controls who were matched for age, sex, and blood pressure values. Microvolt TWA analysis was performed non-invasively using the CH-2000 system during a sub-maximal exercise with the patient sitting on a bicycle ergometer.

RESULTS

The frequency of abnormal TWA was significantly higher in diabetic patients than in controls (25.4 vs 5.7%; P < 0.01). Among diabetic patients, those with abnormal TWA (n = 15) had remarkably higher hemoglobin A1c (HbA1c) (8.1 +/- 0.9 vs 7.1 +/- 0.8%, P < 0.001) and slightly smaller time-domain heart rate variability parameters (i.e., RMSSD, root mean square of difference of successive R-R intervals) than those with normal TWA (n = 44). Gender, age, body mass index, lipids, blood pressure values, cigarette smoking, diabetes duration, microvascular complication status, QTc interval, and current use of medications did not significantly differ between the groups. In multivariate regression logistic analysis, HbA1c (OR 13.6, 95% CI 2.0-89.1; P = 0.0076) predicted abnormal TWA independent of RMSSD values and other potential confounders.

CONCLUSIONS

Our findings suggest that abnormal TWA is a very common condition (approximately 25%) among people with type 2 diabetes without manifest CVD and is closely correlated to glycemic control.

Treating dyslipidaemia in the setting of diabetes mellitus and cardiovascular disease: a less commonly perceived therapeutic perspective in clinical practice

Diabetes mellitus and cardiovascular disease are being managed more belligerently in recent times, with multifactorial cardiovascular risk reduction being the focus of therapeutic interventions. We review some of the caveats to be exercised in the treatment of these patients that are pertinent to clinicians in daily clinical practice.