Does glycemic control reverse dispersion of ventricular repolarization in type 2 diabetes?

Empagliflozin's role in reducing ventricular repolarization heterogeneity: insights into cardiovascular mortality decline from the EMPATHY-HEART trial

BACKGROUND

The incidence of myocardial infarction (MI) and sudden cardiac death (SCD) is significantly higher in individuals with Type 2 Diabetes Mellitus (T2DM) than in the general population. Strategies for the prevention of fatal arrhythmias are often insufficient, highlighting the need for additional non-invasive diagnostic tools. The T-wave heterogeneity (TWH) index measures variations in ventricular repolarization and has emerged as a promising predictor for severe ventricular arrhythmias. Although the EMPA-REG trial reported reduced cardiovascular mortality with empagliflozin, the underlying mechanisms remain unclear. This study investigates the potential of empagliflozin in mitigating cardiac electrical instability in patients with T2DM and coronary heart disease (CHD) by examining changes in TWH.

METHODS

Participants were adult outpatients with T2DM and CHD who exhibited TWH > 80 µV at baseline. They received a 25 mg daily dose of empagliflozin and were evaluated clinically including electrocardiogram (ECG) measurements at baseline and after 4 weeks. TWH was computed from leads V4, V5, and V6 using a validated technique. The primary study outcome was a significant (p < 0.05) change in TWH following empagliflozin administration.

RESULTS

An initial review of 6,000 medical records pinpointed 800 patients for TWH evaluation. Of these, 412 exhibited TWH above 80 µV, with 97 completing clinical assessments and 90 meeting the criteria for high cardiovascular risk enrollment. Empagliflozin adherence exceeded 80%, resulting in notable reductions in blood pressure without affecting heart rate. Side effects were generally mild, with 13.3% experiencing Level 1 hypoglycemia, alongside infrequent urinary and genital infections. The treatment consistently reduced mean TWH from 116 to 103 µV (p = 0.01).

CONCLUSIONS

The EMPATHY-HEART trial preliminarily suggests that empagliflozin decreases heterogeneity in ventricular repolarization among patients with T2DM and CHD. This reduction in TWH may provide insight into the mechanism behind the decreased cardiovascular mortality observed in previous trials, potentially offering a therapeutic pathway to mitigate the risk of severe arrhythmias in this population.

TRIAL REGISTRATION

NCT: 04117763.

Potential favorable action of sodium-glucose cotransporter-2 inhibitors on sudden cardiac death: a brief overview

The primary pharmacological action of sodium-glucose co-transporter 2 (SGLT2) inhibitors is to inhibit the reabsorption of glucose and sodium ions from the proximal tubules of the kidney and to promote urinary glucose excretion. Notably, several clinical trials have recently demonstrated potent protective effects of SGLT2 inhibitors in patients with heart failure (HF) or chronic kidney disease (CKD), regardless of the presence or absence of diabetes. However, the impact of SGLT2 inhibitors on sudden cardiac death (SCD) or fatal ventricular arrhythmias (VAs), the pathophysiology of which is partly similar to that of HF and CKD, remains undetermined. The cardiorenal protective effects of SGLT2 inhibitors have been reported to include hemodynamic improvement, reverse remodeling of the failing heart, amelioration of sympathetic hyperactivity, correction of anemia and impaired iron metabolism, antioxidative effects, correction of serum electrolyte abnormalities, and antifibrotic effects, which may lead to prevent SCD and/or VAs. Recently, as possible direct cardiac effects of SGLT2 inhibitors, not only inhibition of Na⁺/H⁺ exchanger (NHE) activity, but also suppression of late Na⁺ current have been focused on. In addition to the indirect cardioprotective mechanisms of SGLT2 inhibitors, suppression of aberrantly increased late Na⁺ current may contribute to preventing SCD and/or VAs via restoration of the prolonged repolarization phase in the failing heart. This review summarizes the results of previous clinical trials of SGLT2 inhibitors for prevention of SCD, their impact on the indices of electrocardiogram, and the possible molecular mechanisms of their anti-arrhythmic effects.

Characteristics of patients with emergency attendance for severe hypoglycemia and hyperglycemia in a general hospital in Japan

Despite advances in treatments for diabetes mellitus (DM), severe acute glycemic crises still occur. In this study, the characteristics of patients who were transported to an emergency department due to acute glycemic crises were investigated.We enrolled patients who were transported to our hospital by ambulance due to hypoglycemia or hyperglycemia during the period from January 2015 to December 2019. Initial glucose levels below 70 mg/dL and above 250 mg/dL were defined as hypoglycemia and hyperglycemia, respectively.In the 5-year period, 16,910 patients were transported to our hospital by ambulance. Of those patients, 87 patients (0.51%) were diagnosed with hypoglycemia, 26 patients (0.15%) were diagnosed with hyperglycemia and 1 patient was diagnosed with lactic acidosis. Compared to patients with hypoglycemia, blood urea nitrogen, serum potassium and hemoglobin levels were higher in patients with hyperglycemia. Systolic blood pressure was lower and pulse rate was higher in patients with hyperglycemia, possibly reflecting dehydration in hyperglycemia. Patients with hyperglycemia were younger (63 vs 70 years old, median), more likely to be hospitalized (92.3% vs 23.0%) with poorer prognosis (23.1% vs 4.6%) than those with hypoglycemia. In 64 DM patients with hypoglycemia, 34 patients were treated with insulin and 24 patients were treated with sulfonylurea or glinide, and their medication was often inappropriate. Excessive alcohol intake and malnutrition were the main causes of hypoglycemia in 23 non-DM patients. The main reasons for hyperglycemia were interrupted treatment, forgetting insulin injection and infection.To avoid acute glycemic crises, optimization of anti-DM therapy and education of patients are needed.

Myocardial glucotoxicity: Mechanisms and potential therapeutic targets

Besides coronary artery disease, which remains the main cause of heart failure in patients with diabetes, factors independent of coronary artery disease are involved in the development of heart failure in the onset of what is called diabetic cardiomyopathy. Among them, hyperglycaemia - a hallmark of type 2 diabetes - has both acute and chronic deleterious effects on myocardial function, and clearly participates in the establishment of diabetic cardiomyopathy. In the present review, we summarize the cellular and tissular events that occur in a heart exposed to hyperglycaemia, and depict the complex molecular mechanisms proposed to be involved in glucotoxicity. Finally, from a more translational perspective, different therapeutic strategies targeting hyperglycaemia-mediated molecular mechanisms will be detailed.

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.

Investigation of the effect of epicardial adipose tissue thickness on cardiac conduction system in children with type 1 diabetes mellitus

Objectives Investigation of the association between epicardial adipose tissue thickness (EATT) and P-wave dispersion (Pd), QT dispersion (QTd), corrected QT dispersion (QTcd) and Tp-e interval in children with Type 1 Diabetes Mellitus (T1DM) was aimed. Methods Forty-one children with T1DM and 41 age- and gender-matched healthy children were included in the study. Demographical characteristics of all cases were examined. In echocardiography; in addition to conventional echocardiographic measurements, end-systolic EATT was measured from right ventricular free wall. In electrocardiogram; Pd, QTd, QTcd and Tp-e interval durations, as well as Tp-e/QT and Tp-e/QTc ratios were calculated. Correlation values between EATT and electrocardiographic parameters were also noted. Results Mean age of the patient group was determined to be 12.43 ± 3.04 years and that of the control group was determined to be 12.08 ± 2.56 years. There was no significant difference between the groups in regard to age, gender, body weight, height and body mass index. In the patient group; EATT, Pd, QTd, QTcd and Tp-e interval were determined to be significantly higher compared to the control group. In the patient group, no significant correlation was determined between EATT and Pd, QTd, QTcd and Tp-e. However, when both patient and control groups were evaluated together, a statistically significant positive correlation was determined between EATT and Pd, QTd, QTcd and Tp-e. Conclusions In children with T1DM, an increase in epicardial adipose tissue thickness and in risk of cardiac arrhythmias has been demonstrated. To reveal the possible unfavorable effects of EATT on cardiac conduction system in T1DM patients needs further studies.

Insulin Resistance is Associated with Longitudinal Changes of Cardiac Repolarization Heterogeneity in Apparently Healthy Subjects

INTRODUCTION

Increased heterogeneity in ventricular repolarization is a risk factor of sudden cardiac death, but its natural history is unclear. Here we examined whether insulin resistance is associated with longitudinal change in ventricular repolarization heterogeneity in apparently healthy subjects.

METHODS

The study subjects were participants in health checkups in cohort 1 and cohort 2, which were followed up for 6 years and 5 years, respectively. Subjects with diabetes, cardiovascular disease, or renal disease at baseline were excluded from the analyses. As indices of insulin resistance, the homeostasis model assessment of insulin resistance (HOMA-IR) and triglyceride to HDL-cholesterol ratio (TG/HDL-C) were used in cohort 1 and cohort 2, respectively. Heterogeneity in ventricular repolarization was assessed by heart rate-corrected Tpeak-Tend interval in V5 (cTpTe), QT interval, and QT dispersion. In regression analyses, parameters with a skewed distribution were normalized by logarithmic transformation or by Box-Cox transformation.

RESULTS

In longitudinal analyses, Box-Cox-transformed cTpTe at the end of follow-up was weakly correlated with log HOMA-IR at baseline in cohort 1 (n = 153, r = - 0.207, 95% CI - 0.354 to - 0.050, p = 0.010) and with log TG/HDL-C at baseline in cohort 2 (n = 738, r = - 0.098, 95% CI - 0.169 to - 0.026, p = 0.008). Multiple regression analysis showed that indices of insulin resistance, but not glycosylated hemoglobin (HbA1c) or plasma glucose, at baseline were significant explanatory variables for cTpTe at the end of follow-up. Neither QT interval nor QT dispersion was correlated with metabolic parameters.

CONCLUSION

Insulin resistance may be involved in the longitudinal increase of ventricular repolarization heterogeneity in apparently healthy subjects.

Longitudinal impact of dapagliflozin treatment on ventricular repolarization heterogeneity in patients with type 2 diabetes

QTc dispersion (QTcd) tended to be decreased at 24 weeks and was significantly decreased at 2 years after dapagliflozin treatment. In the subgroup with QTcd?53.7 ms (median), QTcd was significantly decreased at 24 weeks and remained improved for 2 years. Dapagliflozin also significantly reduced Tpeak‐Tend/QT in a subgroup with Tpeak‐Tend/QT?0.25 (median).

Zingerone alleviates the delayed ventricular repolarization and AV conduction in diabetes: Effect on cardiac fibrosis and inflammation

Background

The study aims to analyse the action of zingerone in diabetes-related cardiac arrhythmias.

Methods

Diabetes was induced by streptozocin while treatment groups received 20 mg/kg zingerone daily. Following extra seven weeks, electrocardiography, extraction of blood, urine and heart for biochemical analysis, histopathology and immunofluorescence were undertaken.

Results

The suppression of QT and QTc prolongation in diabetic rats was indicative of prolonged cardiac repolarisation that was greatly reduced by zingerone treatment. In addition, the reduction in PR interval attested that zingerone improved AV delay in diabetic rats. The fibrogenic transforming growth factor β1 upregulation in diabetic hearts was suppressed by zingerone. The marked glycogen deposition and muscle degeneration seen in diabetic heart sections were also alleviated by zingerone. Furthermore, zingerone prevented the decrease in of the serum anti-inflammatory cytokine adiponectin in diabetics. The heightened levels of oxidative stress markers 8-isoprostane and uric acid in diabetic rats were suppressed. In the diabetic heart, the reduced catalase activity was improved and the excessive expression of angiotensin receptor 1 was inhibited by zingerone.

Conclusion

Cardiac delayed repolarisation and AV conduction in rats with diabetes were halted by zingerone. It appears that inhibition of cardiac fibrosis and associated inflammation-oxidative stress signalling underpins the zingerone effect.

Effect of sodium-glucose co-transporter-2 inhibitors on impaired ventricular repolarization in people with Type 2 diabetes

AIMS

To test the hypothesis that treatment with a sodium-glucose co-transporter-2 inhibitor would reverse ventricular repolarization heterogeneity, a predictor of cardiovascular mortality, in people with Type 2 diabetes.

METHODS

We retrospectively analysed changes in indices of ventricular repolarization before and after treatment with a sodium-glucose co-transporter-2 inhibitor in 46 people with Type 2 diabetes.

RESULTS

Sodium-glucose co-transporter-2 inhibitor treatment reduced HbA_1c concentration [62±13 mmol/mol (7.7±1.2%) vs 59±16 mmol/mol (7.5±1.4%)], body weight (77.8±13.9 vs 74.7±12.5 kg) and systolic blood pressure (133±18 vs 126±12 mmHg) in the study participants. Heart rate and QTc interval were not changed by sodium-glucose co-transporter-2 inhibitor treatment, but QTc dispersion was significantly reduced (median, 48.8 vs 44.2 ms). Sodium-glucose co-transporter-2 inhibitor treatment reversed QTc dispersion more in participants who had larger QTc dispersion before the treatment. Changes in systolic blood pressure (Spearman's ρ= 0.319; P=0.031), but not in HbA_1c concentration, were correlated with changes in QTc dispersion after sodium-glucose co-transporter-2 inhibitor treatment.

CONCLUSIONS

The findings suggest that sodium-glucose co-transporter-2 inhibitor treatment reverses ventricular repolarization heterogeneity in people with Type 2 diabetes, independently of its effect on glycaemic control. The favourable effect on ventricular repolarization heterogeneity could be the mechanism by which empaglifozin reduced cardiovascular events in a recent study.

Echocardiography and Electrocardiography Variables Correlate With the New York Heart Association classification: An Observational Study of Ischemic Cardiomyopathy Patients

The aim of our study was to determine whether combinations of ultrasound echocardiography (UCG) and electrocardiography (EKG) parameters correlated with the functional status of ischemic cardiomyopathy (ICM) patients according to the New York Heart Association (NYHA) classification system.We assessed 536 elderly Chinese ICM patients according to the NYHA criteria, which included 196 patients with type 2 diabetes mellitus (T2DM). All of the patients underwent UCG. Transmural dispersion of ventricular repolarization was examined using EKG. Cumulative odds logistic regression was performed to evaluate associations between NYHA class and the demographic, clinical, UCG, and EKG variables based on the odds ratio (OR) and 95% confidence interval (CI). A Pearson analysis was also performed to examine correlations between the NYHA classification and the UCG and EKG variables.Based on the NYHA assessment, 140, 147, 138, and 111 patients were identified as class I, II, III and IV, respectively. A comparison of UCG and EKG variables based on T2DM status showed that CO and Tp-e differed significantly between all NYHA classes (P < .05 for all), with values of each increasing with increasing NYHA class regardless of T2DM status. Multivariate logistic regression analysis showed that the disease course (OR: 1.30; 95% CI: 1.20-1.40), heart rate (OR: 1.16; 95% CI: 1.12-1.21), T wave peak to endpoint (Tp-e; OR: 1.22; 95% CI: 1.18-1.27), dispersion of the QT interval (OR: 0.98; 95% CI: 0.95-1.22), left ventricular fractional shortening (OR: 0.82; 95% CI: 0.78-0.87), cardiac output (CO; OR: 5.58; 95% CI: 3.08-10.13) were significantly associated with the NYHA class (P < .0001 for all). A Pearson correlation analysis showed that Tp-e (r = 0.75982, P < .0001), CO (r = 0.56072, P < .0001), and stroke volume (r = -0.14839, P = .0006) significantly correlated with the NYHA class.An index consisting of Tp-e and CO will be useful for corroborating the results of the NYHA assessment of ICM patients.

Hyperglycemia induces defective Ca2+ homeostasis in cardiomyocytes

Diabetes and other metabolic conditions characterized by elevated blood glucose constitute important risk factors for cardiovascular disease. Hyperglycemia targets myocardial cells rendering ineffective mechanical properties of the heart, but cellular alterations dictating the progressive deterioration of cardiac function with metabolic disorders remain to be clarified. In the current study, we examined the effects of hyperglycemia on cardiac function and myocyte physiology by employing mice with high blood glucose induced by administration of streptozotocin, a compound toxic to insulin-producing β-cells. We found that hyperglycemia initially delayed the electrical recovery of the heart, whereas cardiac function became defective only after ~2 mo with this condition and gradually worsened with time. Prolonged hyperglycemia was associated with increased chamber dilation, thinning of the left ventricle (LV), and myocyte loss. Cardiomyocytes from hyperglycemic mice exhibited defective Ca²⁺ transients before the appearance of LV systolic defects. Alterations in Ca²⁺ transients involved enhanced spontaneous Ca²⁺ releases from the sarcoplasmic reticulum (SR), reduced cytoplasmic Ca²⁺ clearance, and declined SR Ca²⁺ load. These defects have important consequences on myocyte contraction, relaxation, and mechanisms of rate adaptation. Collectively, our data indicate that hyperglycemia alters intracellular Ca²⁺ homeostasis in cardiomyocytes, hindering contractile activity and contributing to the manifestation of the diabetic cardiomyopathy.

NEW & NOTEWORTHY

We have investigated the effects of hyperglycemia on cardiomyocyte physiology and ventricular function. Our results indicate that defective Ca²⁺ handling is a critical component of the progressive deterioration of cardiac performance of the diabetic heart.

Ventricular electrical heterogeneity in experimental diabetes mellitus: effect of myocardial ischemia

Aims of the study were to compare the development of electrocardiographic responses of the ischemia-induced heterogeneities of activation and repolarization in the ventricular myocardium of normal and diabetic animals. Body surface ECGs and unipolar electrograms in 64 epicardial leads were recorded before and during 20 min after the ligation of the left anterior descending artery in diabetic (alloxan model, 4 weeks, n=8) and control (n=8) rabbits. Activation times (ATs), end of repolarization times (RTs) and repolarization durations (activation-recovery intervals, ARIs) were determined in ischemic and periischemic zones. In contrast to the controls, the diabetic rabbits demonstrated the significant prolongation of ATs and shortening of ARIs (P<0.05) during ischemia in the affected region resulting in the development and progressive increase of the ARI and RT gradients across the ischemic zone boundary. The alterations of global and local dispersions of the RTs in diabetics correlated with the T(peak)-T(end) interval changes in the limb leads ECGs. In the ischemic conditions, the diabetic animals differed from the controls by the activation delay, significant repolarization duration shortening, and the increase of local repolarization dispersion; the latter could be assessed by the T(peak)-T(end) interval measurements in the body surface ECGs.

Reduction in Kv Current Enhances the Temporal Dispersion of the Action Potential in Diabetic Myocytes: Insights From a Novel Repolarization Algorithm

BACKGROUND

Diabetes is associated with prolongation of the QT interval of the electrocardiogram and enhanced dispersion of ventricular repolarization, factors that, together with atherosclerosis and myocardial ischemia, may promote the occurrence of electrical disorders. Thus, we tested the possibility that alterations in transmembrane ionic currents reduce the repolarization reserve of myocytes, leading to action potential (AP) prolongation and enhanced beat-to-beat variability of repolarization.

METHODS AND RESULTS

Diabetes was induced in mice with streptozotocin (STZ), and effects of hyperglycemia on electrical properties of whole heart and myocytes were studied with respect to an untreated control group (Ctrl) using electrocardiographic recordings in vivo, ex vivo perfused hearts, and single-cell patch-clamp analysis. Additionally, a newly developed algorithm was introduced to obtain detailed information of the impact of high glucose on AP profile. Compared to Ctrl, hyperglycemia in STZ-treated animals was coupled with prolongation of the QT interval, enhanced temporal dispersion of electrical recovery, and susceptibility to ventricular arrhythmias, defects observed, in part, in the Akita mutant mouse model of type I diabetes. AP was prolonged and beat-to-beat variability of repolarization was enhanced in diabetic myocytes, with respect to Ctrl cells. Density of Kv K(+) and L-type Ca(2+) currents were decreased in STZ myocytes, in comparison to cells from normoglycemic mice. Pharmacological reduction of Kv currents in Ctrl cells lengthened AP duration and increased temporal dispersion of repolarization, reiterating features identified in diabetic myocytes.

CONCLUSIONS

Reductions in the repolarizing K(+) currents may contribute to electrical disturbances of the diabetic heart.

Coefficient of variation of R-R interval closely correlates with glycemic variability assessed by continuous glucose monitoring in insulin-depleted patients with type 1 diabetes

AIMS

In type 1 diabetic patients, insulin secretory capacity, meals and physical activity correlate with glycemic variability. Autonomic function associated with gastrointestinal motility and counterregulatory hormone secretion is another candidate which correlates with glucose variability. The aim of this study is to clarify a new clinical parameter associated with glycemic variability in insulin-depleted patients with type 1 diabetes.

METHODS

We studied 31 inpatients with type 1 diabetes. We evaluated glycemic variability calculated by continuous glucose monitoring, clinical parameters and the coefficient of variation of R-R interval (CVR-R). Glycemic variability was also assessed during the daytime and nighttime.

RESULTS

The CVR-R showed a significant negative correlation with the whole-day standard deviation (SD) (r = -0.50, p = 0.007), mean amplitude of glycemic excursions (MAGE) (r = -0.47, p=0.011), M-value (r = -0.38, p = 0.048) and mean of daily differences (MODD) (r = -0.59, p = 0.001). The CVR-R also showed a significant negative correlation with the nighttime SD (r = -0.59, p = 0.001), MAGE (r = -0.47, p=0.011), M-value (r = -0.53, p = 0.004) and MODD (r = -0.65, p = 0.0003). And furthermore, the CVR-R also showed a significant negative correlation with the daytime SD (r = -0.44, p = 0.019) and MAGE (r = -0.50, p = 0.006), but not with the daytime M-value or MODD. The nighttime SD was significantly higher in patients with diabetic polyneuropathy than in patients without it (p = 0.016), while the CVR-R was significantly lower in patients with polyneuropathy than in patients without it (p = 0.009).

CONCLUSIONS

CVR-R is closely correlated with glycemic variability, especially during nighttime, in insulin-depleted patients with type 1 diabetes. Measuring CVR-R may help us to presume the degree of glycemic variability in those patients.

Xanthine oxidase inhibition alleviates the cardiac complications of insulin resistance: effect on low grade inflammation and the angiotensin system

BACKGROUND

We have previously shown that hyperuricemia plays an important role in the vascular complications of insulin resistance (IR). Here we investigated the effect of xanthine oxidase (XO) inhibition on the cardiac complications of IR.

METHODS

IR was induced in rats by a high fructose high fat diet for 12 weeks. Allopurinol, a standard XO inhibitor, was administered in the last 4 weeks before cardiac hemodynamics and electrocardiography, serum glucose, insulin, tumor necrosis factor alpha (TNFα), 8-isoprostane, uric acid, lactate dehydrogenase (LDH) and XO activity were measured. Expression of cardiac angiotensin II (AngII) and angiotensin receptor 1 (AT1) were assessed by immunofluorescence.

RESULTS

IR animals had significant hyperuricemia which was inhibited by allopurinol administration. IR was associated with impaired ventricular relaxation (reflected by a decreased diastolic pressure increment and prolonged diastolic duration) and XO inhibition greatly attenuated impaired relaxation. IR was accompanied by cardiac ischemia (reflected by increased QTc and T peak trend intervals) while XO inhibition alleviated the ECG abnormalities. When subjected to isoproterenol-induced ischemia, IR hearts were less resistant (reflected by larger ST height depression and higher LDH level) while XO inhibition alleviated the accompanying ischemia. In addition, XO inhibition prevented the elevation of serum 8-isoprostane and TNFα, and blocked elevated AngII and AT1 receptor expression in the heart tissue of IR animals. However, XO inhibition did not affect the developed hyperinsulinemia or dyslipidemia.

CONCLUSIONS

XO inhibition alleviates cardiac ischemia and impaired relaxation in IR through the inhibition of low grade inflammation and the angiotensin system.

Dispersion of ventricular repolarization in relation to cardiovascular risk factors in hypertension

RATIONALE

Hypertension associates with sudden cardiac death, its relationship with ventricular arrhythmias being demonstrated by multiple studies, an increased dispersion of repolarization being an important arrhythmogenesis mechanism. Only a small percentage of hypertensive patients presents increased blood pressure values exclusively as risk factor, most of them presenting additional risk factors that reinforce each other leading to increased total cardiovascular risk.

AIM

to analyze the dispersion of repolarization parameters (QT interval, QT dispersion, Tpeak-Tend interval (Tpe), Tpe/QT, Tpe dispersion) in relation to cardiovascular risk factors, as well as total cardiovascular risk estimated by SCORE model, in mild to moderate essential hypertension.

METHOD

62 consecutive patients, mean age 55±11 years, were evaluated by 24 hours Holter electrocardiography monitoring. Manual measurement of dispersion of repolarization parameters was performed.

RESULTS

Based on SCORE model, 33.9% patients presented low risk, 40.3% moderate risk, 16.1% high risk and 9.1% very high risk. Age had a positive correlation with QT and reverse correlations with QT dispersion, Tpe and Tpe/QT in lead V1. Tpe/QT showed significantly higher values in men versus women. Glucose metabolism disorders associated with higher values of QT and Tpe dispersion were present. However, dispersion of repolarization parameters was similar between risk categories assessed by SCORE model, Tpe in lead V3 correlated significantly with SCORE score.

CONCLUSIONS

In mild to moderate hypertension, the dispersion of repolarization parameters is influenced by age, gender and glucose metabolism disorders. Among these, Tpe in lead V3 correlates with total cardiovascular risk assessed by SCORE model.