Sudden cardiac death in diabetes mellitus: risk factors in the Rochester diabetic neuropathy study

Sudden cardiac death due to ventricular arrhythmia in diabetes mellitus: A bench to bedside review

Diabetes mellitus (DM) confers an increased risk of sudden cardiac death (SCD) independent of its associated cardiovascular comorbidities. DM induces adverse structural, electrophysiologic, and autonomic cardiac remodeling that can increase one's risk of ventricular arrhythmias and SCD. Although glycemic control and prevention of microvascular and macrovascular complications are cornerstones in the management of DM, they are not adequate for the prevention of SCD. In this narrative review, we describe the contribution of DM to the pathophysiologic mechanism of SCD beyond its role in atherosclerotic cardiovascular disease and heart failure. On the basis of this pathophysiologic framework, we outline potential preventive and therapeutic strategies to mitigate the risk of SCD in this population of high-risk patients.

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 and in-hospital sudden cardiac arrest in ST-elevation myocardial infarction in the US

Aims

We aimed to assess the impact of diabetes on sudden cardiac arrest (SCA) in US patients hospitalized for ST-elevation myocardial infarction (STEMI).

Methods

We used the National Inpatient Sample (2005-2017) data to identify adult patients with STEMI. The primary outcome was in-hospital SCA. Secondary outcomes included in-hospital mortality, ventricular tachycardia (VT), ventricular fibrillation (VF), cardiogenic shock (CS), acute renal failure (ARF), and the revascularization strategy in SCA patients.

Results

SCA significantly increased from 4% in 2005 to 7.6% in 2018 in diabetes patients and from 3% in 2005 to 4.6% in 2018 in non-diabetes ones (p < 0.001 for both). Further, diabetes was associated with an increased risk of SCA [aOR = 1.432 (1.336-1.707)]. In SCA patients with diabetes, the mean age (SD) decreased from 68 (13) to 66 (11) years old, and mortality decreased from 65.7% to 49.3% during the observation period (p < 0.001). Compared to non-diabetes patients, those with T2DM had a higher adjusted risk of mortality, ARF, and CS [aOR = 1.72 (1.62-1.83), 1.52 (1.43-1.63), 1.25 (1.17-1.33); respectively] but not VF or VT. Those patients were more likely to undergo revascularization with CABG [aOR = 1.197 (1.065-1.345)] but less likely to undergo PCI [aOR = 0.708 (0.664-0.754)].

Conclusion

Diabetes is associated with an increased risk of sudden cardiac arrest in ST-elevation myocardial infarction. It is also associated with a higher mortality risk in SCA patients. However, the recent temporal mortality trend in SCA patients shows a steady decline, irrespective of diabetes.

Cardiovascular autonomic neuropathy is associated with increased glycemic variability driven by hyperglycemia rather than hypoglycemia in patients with diabetes

AIM

Cardiac autonomic neuropathy (CAN) has been suggested to be associated with hypoglycemia and impaired hypoglycemia unawareness. We have assessed the relationship between CAN and extensive measures of glucose variability (GV) in patients with type 1 and type 2 diabetes.

METHODS

Participants with diabetes underwent continuous glucose monitoring (CGM) to obtain measures of GV and the extent of hyperglycemia and hypoglycemia and cardiovascular autonomic reflex testing.

RESULTS

Of the 40 participants (20 T1DM and 20 T2DM) (aged 40.70±13.73 years, diabetes duration 14.43±7.35 years, HbA1c 8.85±1.70%), 23 (57.5%) had CAN. Despite a lower coefficient of variation (CV) (31.26±11.87 vs. 40.33±11.03, P=0.018), they had a higher CONGA (8.42±2.58 vs. 6.68±1.88, P=0.024) with a lower median LBGI (1.60 (range: 0.20-3.50) vs. 4.90 (range: 3.20-7.40), P=0.010) and percentage median time spent in hypoglycemia (4 (range:4-13) vs. 1 (range:0-5), P=0.008), compared to those without CAN. The percentage GRADE_Euglycemia (3.30±2.78 vs. 5.69±3.09, P=0.017) and GRADE_Hypoglycemia (0.3 (range: 0 - 3.80) vs. 1.8 (range: 0.9-6.5), P=0.036) were significantly lower, while the percentage median GRADE_{Hyperglycemia} (95.45 (range:93-98) vs. 91.6 (82.8-95.1), P=0.013) was significantly higher in participants with CAN compared to those without CAN.

CONCLUSION

CAN was associated with increased glycemic variability with less time in euglycemia attributed to a greater time in hyperglycemia but not hypoglycemia.

Risk factors of sudden cardiac death in women: A 10 years study in Tunisia

BACKGROUND

Sudden cardiac death (SCD) represents a frequent etiology of sudden death. It represents a major public health issue. Few data about SCD in women are available from the Arab world. Our work aimed to analyze the risk factors of sudden cardiac death in Tunisian women in comparison with men.

METHODS

A cross-sectional retrospective study including all sudden cardiac death cases, conducted in the Forensic Medicine Department of the main teaching hospital of Tunis, between January 2010 and December 2019.

RESULTS

We counted 417 cases of sudden cardiac death in women representing 17.5% of the total number of sudden cardiac deaths recorded during the study period. The average age was 60.03 ± 15.01 years with a predominance of urban married women. The most frequent cardiac risk factors were high blood pressure (50%), diabetes (36.2%), and cardiac disease history (34.2%). Predominately married women with a history of High blood pressure and diabetes, had a high predictive of sudden cardiac death.

CONCLUSION

Cardiac sudden death is no longer a male focused issue. As a matter of facts Rates of SCD in women are rising with a different pattern. We will highlight the importance of adopting specific preventive measures of SCD in female.

A case of dysautonomia after COVID-19 infection in a patient with poorly controlled type I diabetes

COVID-19 has been linked to dysautonomia in the current literature, as has uncontrolled diabetes. Here, we present a case report of severe dysautonomia following a COVID-19 infection in a patient with pre-existing poorly controlled type-1 diabetes. This patient exhibited symptoms consistent with both postural orthostatic tachycardia syndrome (POTS), as well as orthostatic hypotension. His symptoms became so severe that he was unable to come to a standing position without experiencing syncope. Extensive workup was completed to identify an alternative cause of his dysautonomia with inconclusive results. Dysautonomia can have devastating consequences in regard to physical, social, and psychological health. Counseling individuals with poorly controlled diabetes about the importance of maintaining tight blood glucose control and avoiding COVID-19 infection should be primary interventions when treating patients with this DM1. Early detection and management of diabetes mellitus, COVID-19, and of possible resultant dysautonomia through medical interventions, as well as lifestyle changes, are extremely important measures to avoid development of dangerous and potentially life-threatening consequences.

The association between distal symmetric polyneuropathy in diabetes with all-cause mortality - a meta-analysis

BACKGROUND

Distal symmetric polyneuropathy (DSPN) is a common microvascular complication of both type 1 and 2 diabetes with substantial morbidity burden and reduced quality of life. Its association with mortality is equivocal.

PURPOSE

To describe the association between DSPN and all-cause mortality in people with diabetes and further stratify by the type of diabetes based on a meta-analysis of published observational studies.

DATA SOURCES

We searched Medline from inception to May 2021.

STUDY SELECTION

Original data were collected from case-control and cohort studies that reported on diabetes and DSPN status at baseline and all-cause mortality during follow-up.

DATA EXTRACTION

was completed by diabetes specialists with clinical experience in neuropathy assessment.

DATA SYNTHESIS

Data was synthesized using random-effects meta-analysis. The difference between type 1 and 2 diabetes was investigated using meta-regression.

RESULTS

A total of 31 cohorts (n=155,934 participants, median 27.4% with DSPN at baseline, all-cause mortality 12.3%) were included. Diabetes patients with DSPN had an almost twofold mortality (HR: 1.96, 95%CI: 1.68-2.27, I2 = 91.7%), I^{2 =} 91.7%) compared to those without DSPN that was partly explained by baseline risk factors (adjusted HR: 1.60, 95%CI: 1.37-1.87, I^{2 =} 78.86%). The association was stronger in type 1 compared to type 2 diabetes (HR: 2.22, 95%CI: 1.43-3.45). Findings were robust in sensitivity analyses without significant publication bias.

LIMITATIONS

Not all papers reported multiple adjusted estimates. The definition of DSPN was heterogeneous.

CONCLUSIONS

DSPN is associated with an almost twofold risk of death. If this association is causal, targeted therapy for DSPN could improve life expectancy of diabetic patients.

Ventricular Premature Complexes and Their Associated Factors in a General Population of Japanese Men

Increased ventricular premature complexes (VPCs) are associated with a higher risk of cardiac morbidities. However, little information is available on the risk factors of Western general populations. Therefore, we aimed to assess the frequency and associated factors of VPCs in healthy general Japanese men. We conducted a population-based cross-sectional study in 517 men, aged 40 to 79 years, using 24-hour Holter electrocardiography. Age, body mass index, height, low-density lipoprotein cholesterol, triglycerides, high-density lipoprotein cholesterol, resting heart rate, diabetes mellitus, hypertension, physical activity, smoking, alcohol consumption, lipid-lowering therapy were included in multivariable negative binomial regression to assess independent correlates for the number of VPCs per hour. We observed at least 1 VPC in 1 hour in 429 men (83%). In multivariable negative binomial regression adjusted for all covariates simultaneously, age (risk ratio [95% confidence interval] 1.91 [1.56 to 2.33] per 1-SD increment), height (1.17 [1.04 to 1.49] per 1-SD increment), resting heart rate(1.34 [1.02 to 1.77] per 1-SD increment), diabetes mellitus (2.36 [1.17 to 4.76] ), hypertension (1.90 [1.03 to 3.50]), physical activity (0.67 [0.47 to 0.97] ), current smoking (4.23 [1.86 to 9.60] ), past smoking (2.08 [1.03 to 4.19] ), current light alcohol consumption (0.16 [0.04 to 0.64] ), and lipid-lowering therapy (0.47 [0.23 to 0.96] ) were independently associated with VPCs frequency. In conclusion, VPCs frequency was independently associated with age, height, resting heart rate, diabetes mellitus, hypertension, physical activity, smoking, alcohol consumption, and lipid-lowering therapy.

Machine Learning for Screening Microvascular Complications in Type 2 Diabetic Patients Using Demographic, Clinical, and Laboratory Profiles

Microvascular complications are one of the key causes of mortality among type 2 diabetic patients. This study was sought to investigate the use of a novel machine learning approach for predicting these complications using only the patient demographic, clinical, and laboratory profiles. A total of 96 Bangladeshi participants with type 2 diabetes were recruited during their routine hospital visits. All patient profiles were assessed by using a chi-squared (χ²) test to statistically determine the most important markers in predicting three microvascular complications: cardiac autonomic neuropathy (CAN), diabetic peripheral neuropathy (DPN), and diabetic retinopathy (RET). A machine learning approach based on logistic regression, random forest (RF), and support vector machine (SVM) algorithms was then developed to ensure automated clinical testing for microvascular complications in diabetic patients. The highest prediction accuracies were obtained by RF using diastolic blood pressure, albumin–creatinine ratio, and gender for CAN testing (98.67%); microalbuminuria, smoking history, and hemoglobin A1C for DPN testing (67.78%); and hemoglobin A1C, microalbuminuria, and smoking history for RET testing (84.38%). This study suggests machine learning as a promising automated tool for predicting microvascular complications in diabetic patients using their profiles, which could help prevent those patients from further microvascular complications leading to early death.

Cardiovascular autonomic neuropathy in diabetes: Pathophysiology, clinical assessment and implications

Cardiovascular autonomic neuropathy (CAN) is a debilitating condition that mainly occurs in long-standing type 2 diabetes patients but can manifest earlier, even before diabetes is diagnosed. CAN is a microvascular complication that results from lesions of the sympathetic and parasympathetic nerve fibers, which innervate the heart and blood vessels and promote alterations in cardiovascular autonomic control. The entire mechanism is still not elucidated, but several aspects of the pathophysiology of CAN have already been described, such as the production of advanced glycation end products, reactive oxygen species, nuclear factor kappa B, and pro-inflammatory cytokines. This microvascular complication is an important risk factor for silent myocardial ischemia, chronic kidney disease, myocardial dysfunction, major cardiovascular events, cardiac arrhythmias, and sudden death. It has also been suggested that, compared to other traditional cardiovascular risk factors, CAN progression may have a greater impact on cardiovascular disease development. However, CAN might be subclinical for several years, and a late diagnosis increases the mortality risk. The duration of the transition period from the subclinical to clinical stage remains unknown, but the progression of CAN is associated with a poor prognosis. Several tests can be used for CAN diagnosis, such as heart rate variability (HRV), cardiovascular autonomic reflex tests, and myocardial scintigraphy. Currently, it has already been described that CAN could be detected even during the subclinical stage through a reduction in HRV, which is a non-invasive test with a lower operating cost. Therefore, considering that diabetes mellitus is a global epidemic and that diabetic neuropathy is the most common chronic complication of diabetes, the early identification and treatment of CAN could be a key point to mitigate the morbidity and mortality associated with this long-lasting condition.

The prevalence of cardiac autonomic neuropathy in prediabetes: a systematic review

AIMS/HYPOTHESIS

Cardiac autonomic neuropathy (CAN) is independently associated with silent myocardial ischaemia, major cardiovascular events, myocardial dysfunction and cardiovascular mortality. Several studies have highlighted the increased prevalence of CAN in prediabetes (impaired glucose tolerance and/or impaired fasting glucose). Considering the exponential rise of prediabetes, we aimed to determine the prevalence of CAN through a systematic literature review.

METHODS

This systematic review was registered with PROSPERO (CRD42019125447). An electronic literature search was performed using MEDLINE, EMBASE, PubMed, Web of Science, Scopus and Cochrane databases. Published full text, English language articles that provide CAN prevalence data of studies in individuals with prediabetes and aged over 18 years were included. Prevalence data for normal glucose tolerance and diabetes were also extracted from the selected articles, if present. All articles were screened by two independent reviewers using a priori criteria. Methodological quality and risk of bias were evaluated using a critical appraisal tool.

RESULTS

Database searches found 4500 articles; subsequently, 199 full text articles were screened, 11 of which fulfilled the inclusion criteria (4431 total participants, 1730 people with prediabetes, 1999 people with normal glucose tolerance [NGT] and 702 people with predominantly type 2 diabetes). Six of the selected studies reported definite CAN prevalence data (9-39%). Only a single large population-based study by Ziegler et al (KORA S4 study, 1332 participants) determined definite CAN based on two or more positive autonomic function tests (AFTs), with a mean prevalence of 9% in all prediabetes groups (isolated impaired glucose tolerance 5.9%; isolated impaired fasting glucose 8.1%; impaired fasting glucose plus impaired glucose tolerance 11.4%), which was higher than NGT (4.5%). This study is most likely to provide a reliable population-specific estimate of CAN in prediabetes. There was a higher than expected prevalence of CAN in prediabetes (9-38%) when compared with normal glucose tolerance (0-18%) within the same studies (n = 8). There was a wide prevalence of possible CAN based on one positive AFT (n = 5). There was heterogeneity between the studies with variations in the definition of CAN, methodology and characteristics of the populations, which likely contributed to the diversity of prevalence estimates. The overall risk of bias was low.

CONCLUSIONS/INTERPRETATION

There is a higher than expected prevalence of CAN in prediabetes. Early detection of CAN in prediabetes through population screening needs careful consideration in view of the excess morbidity and mortality risk associated with this condition. Graphical abstract.

Dexmedetomidine exerts neuroprotective effects during high glucose-induced neural injury by inhibiting miR-125b

Diabetic neuropathy (DNP) is the most common complication of diabetes mellitus affecting approximately 50% of diabetes patients. Studying the effect of potential drugs with antioxidant properties and minimal toxicities on neural cells may lead to the development of new and safe pharmacotherapy. Dexmedetomidine (DEX), a highly selective α2-adrenoceptor agonist, is a clinically used sedative also known to have neural protection effect. In the present study, we aimed to investigate the protective role of DEX in high glucose (HG)-induced neural injury and its potential miRNA-related mechanisms. Our results showed that DEX exerted neuroprotective effects during high glucose-induced damage to PC12 cells in a dose-dependent manner. DEX restored cell viability and repressed LDH, Caspase-3 activity, ROS production, and cell apoptosis in HG-treated PC12 cells. MiR-125b-5p was significantly up-regulated in PC12 cells upon HG treatment and it was demonstrated as an target for DEX. The neuroprotective effects of DEX on HG-induced cellular injury were reversed through miR-125b-5p overexpression, and vitamin D receptor (VDR) is a direct targeted of the miR-125b-5p. Together, our results indicate that DEX displays neuroprotective effects on PC-12 cells under high glucose through regulating miR-125b-5p/VDR axis. Our findings might raise the possibility of potential therapeutic application of DEX for managing diabetic neuropathy neural injuries.

Autonomic Nervous System Dysfunction: JACC Focus Seminar

Autonomic nervous system control of the heart is a dynamic process in both health and disease. A multilevel neural network is responsible for control of chronotropy, lusitropy, dromotropy, and inotropy. Intrinsic autonomic dysfunction arises from diseases that directly affect the autonomic nerves, such as diabetes mellitus and the syndromes of primary autonomic failure. Extrinsic autonomic dysfunction reflects the changes in autonomic function that are secondarily induced by cardiac or other disease. An array of tests interrogate various aspects of cardiac autonomic control in either resting conditions or with physiological perturbations from resting conditions. The prognostic significance of these assessments have been well established. Clinical usefulness has not been established, and the precise mechanistic link to mortality is less well established. Further efforts are required to develop optimal approaches to delineate cardiac autonomic dysfunction and its adverse effects to develop tools that can be used to guide clinical decision-making.

Simultaneous Pancreas Kidney Transplantation Improves Cardiovascular Autonomic Neuropathy with Improved Valsalva Ratio as the Most Precocious Test

BACKGROUND

Simultaneous pancreas-kidney (SPK) transplantation is a proven option of treatment for patients with type 1 diabetes mellitus (T1DM) and related end-stage renal disease. There is discrepancy between the results of different studies about the impact of prolonged normalization of glucose metabolism achieved by SPK on the course of diabetic complications including severe forms of diabetic neuropathy. The objective of the study was to evaluate the prevalence of cardiovascular autonomic neuropathy (CAN) in patients undergoing SPK transplantation and its evolution 10 years after transplantation.

METHODS

Prospective study of 81 patients transplanted in a single center from year 2002 to 2015. Autonomic function was assessed using cardiovascular autonomic reflex tests (CARTs). CARTs were made before SPK transplantation and during the follow-up. Evolution of tests after SPK transplantation was evaluated by contrasting hypotheses (paired tests). Multiple testing was adjusted with the Benjamini-Hochberg procedure with a false discovery rate of 10%.

RESULTS

48 males and 33 females, mean age 37.4 ± 5.7 years, mean BMI 24.0 ± 3.4 kg/m², and mean duration of diabetes 25.5 ± 6.5 years, received SPK transplantation. Ten years after SPK transplantation, 56 patients re tained the pancreatic graft (42 of them with normofunctioning pancreas and 14 with low doses of insulin therapy). These 42 patients were selected for the autonomic study. Before transplant procedure, all CART results were abnormal. After SPK transplantation, paired test analysis showed an improvement of systolic blood pressure (SBP) response to orthostasis at the 5^th year after SPK (p = 0.03), as well as improvement of the Valsalva ratio at the 3^rd (p < 0.001) and 5^th (p = 0.001) year after SPK. After correcting for the false discovery rate, all the variables of autonomic study reached significance at different time points.

CONCLUSIONS

Prevalence of CAN in patients who are candidates for SPK transplantation is high and is generally advanced. SPK transplantation improves CAN with improved Valsalva ratio as the most precocious test.

Cardiac Autonomic Neuropathy in Diabetes Mellitus

Cardiovascular autonomic neuropathy (CAN) is a severely debilitating yet underdiagnosed condition in patients with diabetes. The prevalence can range from 2.5% (based on the primary prevention cohort in the Diabetes Control and Complications Trial) to as high as 90% of patients with type 1 diabetes. Clinical manifestations range from orthostasis to myocardial infarction. The diagnosis is made using multiple autonomic function tests to assess both sympathetic and parasympathetic function. The pathophysiology of CAN is complex, likely multifactorial, and not completely understood. Treatment is limited to symptomatic control of orthostatic hypotension, which is a late complication, and current strategies to reverse CAN are limited. This review explores the epidemiology, pathophysiology, clinical manifestations, diagnosis, and complications of CAN as well as current treatment options.

Comparative Safety of Sulfonylureas and the Risk of Sudden Cardiac Arrest and Ventricular Arrhythmia

OBJECTIVE

To examine the association between individual antidiabetic sulfonylureas and outpatient-originating sudden cardiac arrest and ventricular arrhythmia (SCA/VA).

RESEARCH DESIGN AND METHODS

We conducted a retrospective cohort study using 1999-2010 U.S. Medicaid claims from five large states. Exposures were determined by incident use of glyburide, glimepiride, or glipizide. Glipizide served as the reference exposure, as its effects are believed to be highly pancreas specific. Outcomes were ascertained by a validated ICD-9-based algorithm indicative of SCA/VA (positive predictive value ∼85%). Potential confounding was addressed by adjustment for multinomial high-dimensional propensity scores included as continuous variables in a Cox proportional hazards model.

RESULTS

Of sulfonylurea users under study (N = 519,272), 60.3% were female and 34.9% non-Hispanic Caucasian, and the median age was 58.0 years. In 176,889 person-years of sulfonylurea exposure, we identified 632 SCA/VA events (50.5% were immediately fatal) for a crude incidence rate of 3.6 per 1,000 person-years. Compared with glipizide, propensity score-adjusted hazard ratios for SCA/VA were 0.82 (95% CI 0.69-0.98) for glyburide and 1.10 (0.89-1.36) for glimepiride. Numerous secondary analyses showed a very similar effect estimate for glyburide; yet, not all CIs excluded the null.

CONCLUSIONS

Glyburide may be associated with a lower risk of SCA/VA than glipizide, consistent with a very small clinical trial suggesting that glyburide may reduce ventricular tachycardia and isolated ventricular premature complexes. This potential benefit must be contextualized by considering putative effects of different sulfonylureas on other cardiovascular end points, cerebrovascular end points, all-cause death, and hypoglycemia.

Cardiac autonomic neuropathy: Risk factors, diagnosis and treatment

Cardiac autonomic neuropathy (CAN) is a serious complication of diabetes mellitus (DM) that is strongly associated with approximately five-fold increased risk of cardiovascular mortality. CAN manifests in a spectrum of things, ranging from resting tachycardia and fixed heart rate (HR) to development of "silent" myocardial infarction. Clinical correlates or risk markers for CAN are age, DM duration, glycemic control, hypertension, and dyslipidemia (DLP), development of other microvascular complications. Established risk factors for CAN are poor glycemic control in type 1 DM and a combination of hypertension, DLP, obesity, and unsatisfactory glycemic control in type 2 DM. Symptomatic manifestations of CAN include sinus tachycardia, exercise intolerance, orthostatic hypotension (OH), abnormal blood pressure (BP) regulation, dizziness, presyncope and syncope, intraoperative cardiovascular instability, asymptomatic myocardial ischemia and infarction. Methods of CAN assessment in clinical practice include assessment of symptoms and signs, cardiovascular reflex tests based on HR and BP, short-term electrocardiography (ECG), QT interval prolongation, HR variability (24 h, classic 24 h Holter ECG), ambulatory BP monitoring, HR turbulence, baroreflex sensitivity, muscle sympathetic nerve activity, catecholamine assessment and cardiovascular sympathetic tests, heart sympathetic imaging. Although it is common complication, the significance of CAN has not been fully appreciated and there are no unified treatment algorithms for today. Treatment is based on early diagnosis, life style changes, optimization of glycemic control and management of cardiovascular risk factors. Pathogenetic treatment of CAN includes: Balanced diet and physical activity; optimization of glycemic control; treatment of DLP; antioxidants, first of all α-lipoic acid (ALA), aldose reductase inhibitors, acetyl-L-carnitine; vitamins, first of all fat-soluble vitamin B1; correction of vascular endothelial dysfunction; prevention and treatment of thrombosis; in severe cases-treatment of OH. The promising methods include prescription of prostacyclin analogues, thromboxane A2 blockers and drugs that contribute into strengthening and/or normalization of Na+, K+-ATPase (phosphodiesterase inhibitor), ALA, dihomo-γ-linolenic acid (DGLA), ω-3 polyunsaturated fatty acids (ω-3 PUFAs), and the simultaneous prescription of ALA, ω-3 PUFAs and DGLA, but the future investigations are needed. Development of OH is associated with severe or advanced CAN and prescription of nonpharmacological and pharmacological, in the foreground midodrine and fludrocortisone acetate, treatment methods are necessary.

Novel measure of autonomic remodeling associated with sudden cardiac arrest in diabetes

BACKGROUND

Diabetes is independently associated with an increased risk of sudden cardiac arrest (SCA), with a need to identify novel methods for risk stratification. Diabetic patients can develop autonomic dysfunction that has been associated with an increased risk of ventricular arrhythmogenesis and manifests as reduced heart rate variability (HRV). However, previously published studies have not accounted for resting heart rate (HR), important from both pathophysiological and prognosticating standpoints.

OBJECTIVE

We sought to evaluate autonomic remodeling of the sinus node response in SCA and diabetes while accounting for HR.

METHODS

We performed a case-control study in SCA cases (age 35-59 years; 2002-2014) from the ongoing Oregon Sudden Unexpected Death Study (catchment population ∼1 million), and archived 12-lead electrocardiograms recorded prior to the SCA event were compared with those of geographic controls. Short-term HRV was calculated from digitized 10-second electrocardiograms by using established methods. We analyzed 313 subjects (mean age 52.0 ± 5.5 years; 216 men, 69.0%) and compared 4 groups: 111 diabetic (49 cases, 62 controls) and 202 nondiabetic (80 cases, 122 controls) subjects.

RESULTS

Analysis of covariance showed an absence of the expected interaction between HRV and HR (HRV-HR) in diabetic patients with SCA (regression slope -0.008; 95% confidence interval -0.023 to 0.0071; P = .26). This finding, unique to this population of diabetic patients with SCA, was not detected using traditional HRV measures.

CONCLUSION

By incorporating resting HR in this analysis, we observed that this population of diabetic patients with SCA had loss of the expected HRV-HR relationship. This potentially novel noninvasive risk measurement warrants further investigation, especially at the level of the individual patient.

Pro- and Antiarrhythmic Actions of Sulfonylureas: Mechanistic and Clinical Evidence

Sulfonylureas are the most commonly used second-line drug class for treating type 2 diabetes mellitus (T2DM). While the cardiovascular safety of sulfonylureas has been examined in several trials and nonrandomized studies, little is known of their specific effects on sudden cardiac arrest (SCA) and related serious arrhythmic outcomes. This knowledge gap is striking, because persons with DM are at increased risk of SCA. In this review, we explore the influence of sulfonylureas on the risk of serious arrhythmias, with specific foci on ischemic preconditioning, cardiac excitability, and serious hypoglycemia as putative mechanisms. Elucidating the relationship between individual sulfonylureas and serious arrhythmias is critical, especially as the diabetes epidemic intensifies and SCA incidence increases in persons with diabetes.

Is High Serum LDL/HDL Cholesterol Ratio an Emerging Risk Factor for Sudden Cardiac Death? Findings from the KIHD Study

AIM

Low-density lipoprotein cholesterol (LDL-c) and high-density lipoprotein cholesterol (HDL-c), which are components of total cholesterol, have each been suggested to be linked to the risk of sudden cardiac death (SCD). However, the relationship between LDL-c/HDL-c ratio and the risk of SCD has not been previously investigated. We aimed to assess the associations of LDL-c, HDL-c, and the ratio of LDL-c/HDL-c with the risk of SCD.

METHODS

Serum lipoprotein concentrations were assessed at baseline in the Finnish Kuopio Ischemic Heart Disease prospective cohort study of 2,616 men aged 42-61 years at recruitment. Hazard ratios (HRs) (95% confidence intervals [CI]) were assessed.

RESULTS

During a median follow-up of 23.0 years, a total of 228 SCDs occurred. There was no significant evidence of an association of LDL-c or HDL-c with the risk of SCD. In analyses adjusted for age, examination year, body mass index, systolic blood pressure, smoking, alcohol consumption, physical activity, years of education, diabetes, previous myocardial infarction, family history of coronary heart disease, and serum high sensitivity C-reactive protein, there was approximately a two-fold increase in the risk of SCD (HR 1.94, 95% CI 1.21-3.11; p=0.006), comparing the top (＞4.22) versus bottom (≤2.30) quintile of serum LDL-c/HDL-c ratio.

CONCLUSION

In this middle-aged male population, LDL-c or HDL-c was not associated with the risk of SCD. However, a high serum LDL-c/HDL-c ratio was found to be independently associated with an increased risk of SCD. Further research is warranted to understand the mechanistic pathways underlying this association.

Analysis of the association between glucose profiles and β-cell function for diabetic cardiovascular autonomic neuropathy in China

AIMS/INTRODUCTION

The purpose of the present study was to investigate the severity of glucose profiles and β-cell function associated with diabetic cardiovascular autonomic neuropathy (DCAN) in a Chinese sample.

MATERIALS AND METHODS

A community-based, cross-sectional study to analyze the risk factors of DCAN was carried out with 455 individuals recruited from a Chinese population. The glucose profile risk score was calculated to identify the association between the severity of the glucose profiles and DCAN. The associations of the severity of the glucose profiles and β-cell function with DCAN were analyzed using multivariable logistic regression.

RESULTS

Univariate analysis showed that the glucose profiles and homeostatic model assessment of insulin resistance were significantly associated with the DCAN outcome, respectively. Multivariable logistic regression showed that significant associations exist between glucose profile indices and DCAN, after controlling for potential confounding factors (P < 0.01 for all) in both models. Multivariable logistic regression also showed that parameters of β-cell function were associated with the DCAN outcome in the category model (P < 0.1 for all). The glucose profile risk score was independently and significantly associated with the DCAN outcome after controlling for confounding factors (P < 0.001 and P for a trend <0.001).

CONCLUSIONS

Our observations suggest that parameters of glucose profile indices and β-cell function are significantly and independently associated with DCAN, respectively. There was a tendency toward increased glucose profile risk score with increasing prevalence of DCAN.

Association between Clinical and Doppler Echocardiographic Parameters with Sudden Death in Hemodialysis Patients

BACKGROUND

Sudden cardiac death (SCD) is the leading cause of death in maintenance hemodialysis (HD) patients, but there is little information about underlying risk factors.

OBJECTIVES

Evaluate the association between clinical and echocardiographic variables with SCD on HD patients.

METHODS

Retrospective nested case-control study on chronic HD patients who were prospectively followed. The primary endpoint was SCD. Variables were compared by Student t test, Mann-Whitney or Chi-Square, and independent predictors of SCD were evidenced by multivariate logistic regression.

RESULTS

We followed 153 patients (50 ± 15 years, 58% men) for 23 ± 14 months and observed 35 deaths, 17 of which were SCD events. When compared to the control group (matched for gender, age, and body mass index) there were no differences regarding time on dialysis, traditional biochemical parameters, blood pressure, smoking, use of cardiovascular protective drugs, ejection fraction, left ventricular dimensions, and diastolic function indices. On the other hand, in the SCD group, we found a higher prevalence of previous heart failure, acute myocardial infarction and diabetes, greater left ventricular mass index, greater left atrial size and lower global myocardial performance. After multivariate logistic regression analysis, diabetes (OR = 2.6; CI = 1.3-7.5; p = 0.023) and left ventricular mass index ≥ 101 g/m2.7 (OR = 1.04; CI = 1.01-1.08; p = 0.028) showed independent association with SCD events.

CONCLUSIONS

HD patients with diabetes mellitus and left ventricular hypertrophy appear to have the highest risk of SCD. Preventive and therapeutic strategies should be encouraged in addressing these risk factors to minimize the occurrence of SCD in HD patients.

Autonomic Neuropathy and Endothelial Dysfunction in Patients With Impaired Glucose Tolerance or Type 2 Diabetes Mellitus

Autonomic neuropathy is one of the most common complications of diabetes mellitus (DM). The etiology of autonomic impairment is not well-understood, yet. There is need for studies to investigate the cause-effect relationships of inflammation and/or endothelial dysfunction and diabetic autonomic neuropathy. Only a few reports have mentioned autonomic neuropathy in individuals with impaired glucose tolerance (IGT), previously. Furthermore, the association between the plasma markers of endothelial dysfunction (von Willebrand factor (vWF), soluble E-selectin) and autonomic neuropathy in patients with IGT or DM has not been studied before. In this study, we aimed to investigate the correlation between plasma markers of endothelial dysfunction and autonomic neuropathy in patients with IGT or type 2 DM (T2DM).In this case-control study, 25 IGT patients, 25 T2DM patients with autonomic symptoms, and 30 controls were included. Demographical data, HbA1c, vWF, and soluble E-selectin (sE-selectin) levels were analyzed. Sympathetic skin response (SSR) and heart rate variability (HRV) were used as the indicator of autonomic activity.Plasma levels of HbA1c, vWF, and sE-selectin were higher in patients with IGT than the controls; patients with T2DM had higher levels than both the controls and the patients with IGT. SSR measures were similar among the groups. However, higher number of T2DM patients had absent plantar SSR than controls. HRV analysis at rest revealed lower standard deviation of R-R interval, coefficient of variation of R-R interval, low-frequency (LF) power and total power in patients with IGT and T2DM than the controls. In addition, HRV analysis at deep breathing showed lower high-frequency (HF) power in IGT group. LF:HF ratio was lower in both patient groups at rest. No strong correlation was found between the levels of HbA1c, vWF, sE-selectin, HRV, and SSR measures.Our results support that endothelial dysfunction is evident in individuals with IGT or T2DM and HRV is impaired in early stages in the course of T2DM. However, increased levels of biomarkers of endothelial damage do not correlate with HRV or SSR. More studies are needed to clarify the disease pathogenesis and its clinical correlates. Impaired HRV in T2DM could be due to mechanisms other than endothelial dysfunction.

A novel quantitative method for diabetic cardiac autonomic neuropathy assessment in type 1 diabetic mice

In this work, we used a sensitive and noninvasive computational method to assess diabetic cardiovascular autonomic neuropathy (DCAN) from pulse oximeter (photoplethysmographic; PPG) recordings from mice. The method, which could be easily applied to humans, is based on principal dynamic mode (PDM) analysis of heart rate variability (HRV). Unlike the power spectral density, PDM has been shown to be able to separately identify the activities of the parasympathetic and sympathetic nervous systems without pharmacological intervention. HRV parameters were measured by processing PPG signals from conscious 1.5- to 5-month-old C57/BL6 control mice and in Akita mice, a model of insulin-dependent type 1 diabetes, and compared with the gold-standard Western blot and immunohistochemical analyses. The PDM results indicate significant cardiac autonomic impairment in the diabetic mice in comparison to the controls. When tail-cuff PPG recordings were collected and analyzed starting from 1.5 months of age in both C57/Bl6 controls and Akita mice, onset of DCAN was seen at 3 months in the Akita mice, which persisted up to the termination of the recording at 5 months. Western blot and immunohistochemical analyses also showed a reduction in nerve density in Akita mice at 3 and 4 months as compared to the control mice, thus, corroborating our PDM data analysis of HRV records. Western blot analysis of autonomic nerve proteins corroborated the PPG-based HRV analysis via the PDM approach. In contrast, traditional HRV analysis (based on either the power spectral density or time-domain measures) failed to detect the nerve rarefaction.

Protein kinase RNA-like endoplasmic reticulum kinase (PERK)/calcineurin signaling is a novel pathway regulating intracellular calcium accumulation which might be involved in ventricular arrhythmias in diabetic cardiomyopathy

We previously found that endoplasmic reticulum (ER) stress was involved in ventricular arrhythmias in diabetic cardiomyopathy. The present study was aimed to investigate the possible mechanism. In the in vivo study, diabetes cardiomyopathy (DCM) was induced by streptozotocin (STZ) injection. Hemodynamic and plasma brain natriuretic peptide (BNP) detections were used to evaluate cardiac functions; ECG was used to assess the vulnerability to arrhythmias by recording ventricular arrhythmia events (VAEs). In the in vitro study, high-glucose incubation was employed to mimic the diabetic environment of myocytes. Immunofluorescent staining was used to investigate the nuclear factor of activated T cells (NFAT) nuclear translocation and (FK506-binding protein 12.6) FKBP12.6 disassociation. [(3)H]-ryanodine binding assay was implemented to assess the channel activity of ryanodine receptor. In both in vivo and in vitro studies, activity of calcineurin was determined by colorimetric method, and western blotting was used to detect protein expression levels. In the in vivo study, we found that inhibition of both of ER stress and PERK activation decreased the VAEs in DCM rats, accompanied by reduced activity of calcineurin in myocardial tissue. In the in vitro study, in high-glucose incubated myocytes, the depletion of PERK reduced activity of calcineurin, decreased NFAT translocation and FKBP12.6 disassociation from ryanodine receptor 2 (RyR2). Furthermore, PERK deletion also reduced RyR2 channel activity and consequently impaired intracellular calcium accumulation. We concluded that PERK/calcineurin-pathway was involved in intracellular calcium regulation in myocytes in diabetic heart, which might be the mechanism inducing arrhythmias in DCM.

Cardiac autonomic neuropathy in patients with diabetes mellitus

Cardiac autonomic neuropathy (CAN) is an often overlooked and common complication of diabetes mellitus. CAN is associated with increased cardiovascular morbidity and mortality. The pathogenesis of CAN is complex and involves a cascade of pathways activated by hyperglycaemia resulting in neuronal ischaemia and cellular death. In addition, autoimmune and genetic factors are involved in the development of CAN. CAN might be subclinical for several years until the patient develops resting tachycardia, exercise intolerance, postural hypotension, cardiac dysfunction and diabetic cardiomyopathy. During its sub-clinical phase, heart rate variability that is influenced by the balance between parasympathetic and sympathetic tones can help in detecting CAN before the disease is symptomatic. Newer imaging techniques (such as scintigraphy) have allowed earlier detection of CAN in the pre-clinical phase and allowed better assessment of the sympathetic nervous system. One of the main difficulties in CAN research is the lack of a universally accepted definition of CAN; however, the Toronto Consensus Panel on Diabetic Neuropathy has recently issued guidance for the diagnosis and staging of CAN, and also proposed screening for CAN in patients with diabetes mellitus. A major challenge, however, is the lack of specific treatment to slow the progression or prevent the development of CAN. Lifestyle changes, improved metabolic control might prevent or slow the progression of CAN. Reversal will require combination of these treatments with new targeted therapeutic approaches. The aim of this article is to review the latest evidence regarding the epidemiology, pathogenesis, manifestations, diagnosis and treatment for CAN.

The association of ECG and echocardiographic abnormalities with sudden cardiac death in a dialysis patient cohort

BACKGROUND

Cardiovascular mortality is greater in dialysis patients than the general population. More specifically, sudden cardiac death (SCD) accounts for 26% of dialysis patient deaths. However, SCD risk assessment tools used in the general population are not adequate for dialysis patients indicating that the hierarchy of pathopysiological factors appears to be different. The aim of this study was to use simple bedside tests to determine parameters independently predictive of cardiovascular mortality and SCD in dialysis patients.

METHOD AND RESULTS

This was a sub-study of the Chronic Renal Insufficient Standards Implementations Study, a longitudinal cohort study of outcomes in CKD. ECG and echocardiographic abnormalities were assessed in a cross-section of prevalent dialysis patients. Patients were followed up until death or transplantation. Forward stepwise Cox regression then determined factors independently associated with all-cause, cardiovascular and SCD mortality. 323 patients were included (age 61.5 ± 14.6 years, 113 deaths, 66 cardiovascular deaths, 18 SCD). A number of factors were independently associated with all-cause mortality. These were age, time on dialysis, smoking, the difference between QRS and T-wave axes, resting heart rate, and pulmonary artery pressure (PAP) >35 mmHg. The only parameters predictive of SCD were elevated PAP (HR = 5.99, p = 0.05) and mitral regurgitation (HR = 6.71, p = 0.01).

CONCLUSION

That PAP is associated with SCD in dialysis patients demonstrates that the pathophysiological mechanism is likely to be different in these patients compared to the general population. Because of this, a population specific approach to risk stratification is advisable.

Autonomic neuropathy in HIV is unrecognized and associated with medical morbidity

Autonomic dysfunction is common in HIV. However, its clinical impact is not well understood and its protean symptoms make it difficult to diagnose. We sought to determine: (1) whether autonomic neuropathy is associated with morbidity and predicted mortality in HIV as measured by the Veterans Aging Cohort Study (VACS) index; and (2) if healthcare providers recognize the diagnosis of autonomic neuropathy. Data were obtained from 102 HIV-infected adults enrolled in a prevalence study of autonomic dysfunction from 2011-2012. Participants were predominantly minority with nearly equal numbers of men and women. Most were receiving an antiretroviral regimen with a nucleoside reverse transcriptase inhibitor backbone and a base of a non-nucleoside reverse transcriptase inhibitor, protease inhibitor, or integrase inhibitor. Autonomic neuropathy was defined using a laboratory-based autonomic assessment, the Composite Autonomic Severity Score (CASS). Medical records were reviewed for the year prior to the autonomic assessment. We found that the autonomic neuropathy score (CASS) was associated with the VACS index. We also found that among 53 participants with symptomatic autonomic neuropathy, the diagnosis had been considered for only one. The majority of the symptoms were either unexplained or attributed to medication side effects. This study demonstrates that autonomic neuropathy in HIV is associated with serious co-morbid illnesses known to increase mortality risk, and that HIV healthcare providers rarely consider autonomic neuropathy in their differential diagnoses. Future studies are needed to determine if autonomic neuropathy is an independent risk factor for mortality in HIV, and to raise awareness of its signs and symptoms.

Autonomic dysfunction is common in HIV and associated with distal symmetric polyneuropathy

Neurologic complications of HIV are well characterized in the central and peripheral nervous systems but not in the autonomic nervous system, perhaps due to the complexities of measuring autonomic function in medically ill populations. We hypothesized that autonomic dysfunction is common in HIV, can be meaningfully measured with an autonomic reflex screen, and is associated with distal symmetric polyneuropathy (DSP) but not with signs of CNS disease. We also sought to characterize immunovirologic and medical factors associated with autonomic dysfunction. We assessed 102 HIV-infected adults for autonomic dysfunction with a laboratory-based autonomic reflex screen summarized as the composite autonomic severity score (CASS). The total neuropathy score (TNS) was used to quantify DSP based on neurologic interview/examination, quantitative sensory testing, and nerve conduction studies. Autonomic dysfunction was common, with a CASS  ≥  3 in 61 % of participants, of whom 86 % were symptomatic. Greater CASS abnormalities demonstrated univariate association with increasing TNS, age, viral load, hypertension, and use of medications (particularly anticholinergics), but not with antiretrovirals, current/nadir CD(4+) count, HIV duration, metabolic factors, or signs of CNS disease. The TNS was the only significant predictor of the CASS in multivariate analysis; anticholinergic medications were marginally significant. This study demonstrates that autonomic dysfunction is common and frequently symptomatic in HIV and that an autonomic reflex screen, adjusted for anticholinergic medication, is useful in its assessment. Association of autonomic dysfunction with DSP suggests common factors in their pathogenesis, and autonomic neuropathy may be part of the spectrum of HIV-associated peripheral nerve pathologies.

Diabetic autonomic neuropathy

Autonomic neuropathy, once considered to be the Cinderella of diabetes complications, has come of age. The autonomic nervous system innervates the entire human body, and is involved in the regulation of every single organ in the body. Thus, perturbations in autonomic function account for everything from abnormalities in pupillary function to gastroparesis, intestinal dysmotility, diabetic diarrhea, genitourinary dysfunction, amongst others. "Know autonomic function and one knows the whole of medicine!" It is now becoming apparent that before the advent of severe pathological damage to the autonomic nervous system there may be an imbalance between the two major arms, namely the sympathetic and parasympathetic nerve fibers that innervate the heart and blood vessels, resulting in abnormalities in heart rate control and vascular dynamics. Cardiac autonomic neuropathy (CAN) has been linked to resting tachycardia, postural hypotension, orthostatic bradycardia and orthostatic tachycardia (POTTS), exercise intolerance, decreased hypoxia-induced respiratory drive, loss of baroreceptor sensitivity, enhanced intraoperative or perioperative cardiovascular lability, increased incidence of asymptomatic ischemia, myocardial infarction, and decreased rate of survival after myocardial infarction and congestive heart failure. Autonomic dysfunction can affect daily activities of individuals with diabetes and may invoke potentially life-threatening outcomes. Intensification of glycemic control in the presence of autonomic dysfunction (more so if combined with peripheral neuropathy) increases the likelihood of sudden death and is a caveat for aggressive glycemic control. Advances in technology, built on decades of research and clinical testing, now make it possible to objectively identify early stages of CAN with the use of careful measurement of time and frequency domain analyses of autonomic function. Fifteen studies using different end points report prevalence rates of 1% to 90%. CAN may be present at diagnosis, and prevalence increases with age, duration of diabetes, obesity, smoking, and poor glycemic control. CAN also cosegregates with distal symmetric polyneuropathy, microangiopathy, and macroangiopathy. It now appears that autonomic imbalance may precede the development of the inflammatory cascade in type 2 diabetes and there is a role for central loss of dopaminergic restraint on sympathetic overactivity. Restoration of dopaminergic tone suppresses the sympathetic dominance and reduces cardiovascular events and mortality by close to 50%. Cinderella's slipper can now be worn!

Influence of obesity indices, metabolic parameters and age on cardiac autonomic function in abdominally obese men

Heart rate variability (HRV) is affected by age, hyperglycemia and accumulation of body fat. This study compares the predictive value of four measurements of adiposity/obesity on HRV and investigates the specific role of age, metabolic contributors and degree/distribution of fat in HRV alterations. The sample consisted of 97 non-diabetic and non-medicated men with features of the metabolic syndrome (50±8 years of age, body mass index [BMI] 31±3 kg/m(2), waist circumference [WC] 107±9 cm, triglycerides 2.3±0.7 mmol/L, fasting glucose 6.0±0.5 mmol/L, insulin 156±71 pmol/L; mean±SD). WC, BMI, percent body fat (% fat, from dual energy X-ray absorptiometry) and visceral adipose tissue volume (VAT, from computed tomography) were used as measures of adiposity/obesity. HRV measures were obtained from 24-h, day- and night-time segments of Holter recordings. BMI presented no independent association with HRV. Percentage fat was the strongest obesity index to be associated with HRV: 24-h pNN50, rMSSD, HF and daytime pNN50, rMSSD, HF and LF (-0.27≤std β≤-0.20, P<.05). VAT was associated with 24-h SDNN, LF (std β=-0.25 and -0.20, P<.05, respectively) and daytime SDNN (std β=-0.24, P<.05) while WC was associated with nighttime SDNN and SDANN (std β=0.22 and 0.32, P<.05). In addition, age, fasting glucose, 2-h oral glucose tolerance test and triglycerides presented independent association with HRV. Adiposity/obesity measurements seem to be differently associated with HRV. An approach considering the combination of age, obesity and glucose metabolism factors could be helpful in the global cardiovascular risk management in abdominally obese men.

Cardiovascular autonomic neuropathy and subclinical cardiovascular disease in normoalbuminuric type 1 diabetic patients

Cardiovascular autonomic neuropathy (CAN) is associated with increased mortality in diabetes. Since CAN often develops in parallel with diabetic nephropathy as a confounder, we aimed to investigate the isolated impact of CAN on cardiovascular disease in normoalbuminuric patients. Fifty-six normoalbuminuric, type 1 diabetic patients were divided into 26 with (+) and 30 without (-) CAN according to tests of their autonomic nerve function. Coronary artery plaque burden and coronary artery calcium score (CACS) were evaluated using computed tomography. Left ventricular function was evaluated using echocardiography. Blood pressure and electrocardiography were recorded through 24 h to evaluate nocturnal drop in blood pressure (dipping) and pulse pressure. In patients +CAN compared with -CAN, the CACS was higher, and only patients +CAN had a CACS >400. A trend toward a higher prevalence of coronary plaques and flow-limiting stenosis in patients +CAN was nonsignificant. In patients +CAN, left ventricular function was decreased in both diastole and systole, nondipping was more prevalent, and pulse pressure was increased compared with -CAN. In multivariable analysis, CAN was independently associated with increased CACS, subclinical left ventricular dysfunction, and increased pulse pressure. In conclusion, CAN in normoalbuminuric type 1 diabetic patients is associated with distinct signs of subclinical cardiovascular disease.

Sudden cardiac death in hemodialysis patients: an in-depth review

Sudden cardiac death (SCD) is the leading cause of death in hemodialysis patients, accounting for death in up to one-quarter of this population. Unlike in the general population, coronary artery disease and heart failure often are not the underlying pathologic processes for SCD; accordingly, current risk stratification tools are inadequate when assessing these patients. Factors assuming greater importance in hemodialysis patients may include left ventricular hypertrophy, electrolyte shift, and vascular calcification. Knowledge regarding SCD in hemodialysis patients is insufficient, in part reflecting the lack of an agreed-on definition of SCD in this population, although epidemiologic studies suggest the most common times for SCD to occur are toward the end of the long 72-hour weekend interval between dialysis sessions and in the 12 hours immediately after hemodialysis. Accordingly, it is hypothesized that the dialysis procedure itself may have important implications for SCD. Supporting this is recognition that hemodialysis is associated with both ventricular arrhythmias and dynamic electrocardiographic changes. Importantly, echocardiography and electrocardiography may show changes that are modifiable by alterations to dialysis prescription. The most effective preventative strategy in the general population, implanted cardioverter-defibrillator devices, are less effective in the presence of chronic kidney disease and have not been studied adequately in dialysis patients. Last, many dialysis patients experience SCD despite not fulfilling current criteria for implantation, making appropriate allocation of defibrillators uncertain.

Associations between cardio-ankle vascular index and microvascular complications in type 2 diabetes mellitus patients

AIM

Type 2 diabetes mellitus (T2DM) is a risk factor for increased arterial stiffness. We evaluated associations between the cardio-ankle vascular index (CAVI) and carotid plaque, intima media thickness (IMT), and diabetic microvascular complications in Korean T2DM patients.

METHODS

We conducted a retrospective, cross-sectional study of 320 Korean T2DM patients without a history of macrovascular disease or macroalbuminuria. We measured 24-hour urinary albumin excretion (UAE) levels and performed funduscopic and neuropathy examinations to assess the extent of diabetic microvascular complications. Arterial stiffness was assessed using CAVI. We also measured the ankle-brachial index (ABI), common carotid artery IMT, and carotid beta stiffness index.

RESULTS

Among the 320 patients enrolled in this study, 64 (20%) had increased CAVI (≥ 9). We found that CAVI was correlated with systolic blood pressure, pulse pressure, IMT, carotid beta stiffness index, log-transformed UAE, and total cholesterol. In multiple logistic regression analysis, mean IMT and the presence of carotid plaque were independently associated with increased CAVI (≥ 9) (OR=5.77, P < 0.01; OR=5.36, P < 0.001, respectively). Furthermore, an increased CAVI was associated with peripheral neuropathy (OR=2.03, P = 0.03) and microalbuminuria (OR=2.47, P < 0.01) after adjusting for possible confounding variables.

CONCLUSIONS

The results of this study suggest that increased CAVI is associated with the presence of arterial plaque, increased IMT, and microvascular complications, such as nephropathy and neuropathy, in T2DM patients.

Ventricular arrhythmias and sudden death in patients with chronic kidney disease

One in four dialysis patients will die suddenly. Most do not fall into the high-risk categories that are associated with sudden death in the general population. The cause of sudden death in the dialysis population is unknown. It may be related to factors associated with chronic kidney disease (CKD) itself, for example, inflammation, vascular stiffness, left ventricular hypertrophy, coronary artery disease, electrolyte/fluid abnormalities or autonomic dysfunction. Studies of patients with implantable cardioverter defibrillators have shown that patients with CKD are more likely to use their devices for ventricular arrhythmias but in spite of this still have a high associated mortality. Until a comprehensive risk stratification strategy is understood, minimising risk by good control of basic parameters such as fluid balance, electrolytes and blood pressure, along with careful assessment of all patients for evidence of coronary artery disease and heart failure is the mainstay of management of the CKD patient.

Streptozotocin-induced diabetes modulates action potentials and ion channel currents from the rat atrioventricular node

The present study was conducted to evaluate whether experimentally induced type 1 diabetes results in alterations to atrioventricular nodal (AVN) electrophysiology at the cellular level. Spontaneous action potentials (APs) and ionic currents were recorded from AVN myocytes isolated from the hearts of control rats and from those with streptozotocin-induced diabetes. Perforated patch-clamp recordings were used to assess changes in cellular AP parameters and in ionic currents. Type 1 diabetes significantly increased AP duration, whilst reducing AP firing rate, upstroke velocity and rate of diastolic depolarization. The diabetes-induced changes in AP parameters were accompanied by a significant leftward shift in the zero current potential under voltage clamp, a reduction in peak L-type Ca(2+) current density and reduced amplitude of delayed rectifier and hyperpolarization-activated currents. These findings demonstrate that experimentally induced type 1 diabetes can lead to remodelling of AVN cellular electrophysiology.

Type 2 diabetes mellitus and the risk of sudden cardiac arrest in the community

The reduction of mortality from sudden cardiac arrest (SCA) in the setting of coronary heart disease (CHD) remains a major challenge, especially among patients with type 2 diabetes. Diabetes is associated with an increased risk of SCA, at least in part, from an increased presence and extent of coronary atherosclerosis (macrovascular disease). Diabetes also is associated with microvascular disease and autonomic neuropathy; and, these non-coronary atherosclerotic pathophysiologic processes also have the potential to increase the risk of SCA. In this report, we review the absolute and relative risk of SCA associated with diabetes. We summarize recent evidence that suggests that the increase in risk in patients with diabetes is not specific for SCA, as diabetes also is associated with a similar increase in risk for non-SCA CHD death and non-fatal myocardial infarction. These data are consistent with prior observations that coronary atherosclerosis is a major contributor to the increased SCA risk associated with diabetes. We also present previously published and unpublished data that demonstrates that both clinically-recognized microvascular and autonomic neuropathy also are associated with the risk of SCA among treated patients with diabetes, after taking into account prior clinically-recognized heart disease and other risk factors for SCA. We then discuss how these data might inform research and clinical efforts to prevent SCA. Although the prediction of SCA in this "high" risk population is likely to remain a challenge, as it is in other "high" risk clinical populations, we suggest that current recommendations for the prevention of SCA in the community, related to both lifestyle prescriptions and risk factor reduction, are likely to reduce mortality from SCA among patients with diabetes.

[Pathophysiology and treatment for diabetic neuropathy]

Diabetic neuropathy (DN) is the most frequent among peripheral neuropathies. Since its pathophysiology is so complicated, neither classification nor therapeutic management of DN has been established. Sensory/autonomic polyneuropathy (DP) is the main type of DN. Since diabetic patients occasionally have one or more subtypes of DN and/or other polyneuropathy including treatable neuropathy like CIDP, the treatment for DP has to be conducted after excluding the possibility of other conditions. Glycemic control is most essential to prevent the development of DP. However, it is practically difficult to keep HbA1c under 6.5% so that drinking and smoking better be restricted and blood pressure be properly maintained to retard the progression of DP. Aldose reductase inhibitor is only one commercially available drug for DP and its efficacy must be evaluated by nerve function tests along with subjective symptoms. More vigorous therapeutic procedure is expected by obtaining not only more potential drugs based on pathogenic mechanisms but also the technique targeting of DNA/siRNA of given peptides at dorsal root ganglion neurons.

A combined abnormality in heart rate variation and QT corrected interval is a strong predictor of cardiovascular death in type 1 diabetes

OBJECTIVE

Long-term diabetes is associated with excess morbidity and mortality, and cardiovascular autonomic neuropathy and QTc interval abnormalities are both predictive of early cardiovascular death in diabetes. We aimed to investigate the effect of these risk factors in a large cohort of type 1 diabetic patients followed prospectively for 10 years.

MATERIAL AND METHODS

Three-hundred-and-ninety-one type 1 diabetic mellitus patients (240 M and 151 F, age 41.8 years +/- 9.9 (mean +/-SD), duration of DM 27.3 years +/- 8.2) were followed in an outpatient setting.

RESULTS

Patients with decreased heart rate variability had an excess overall mortality that diminished after adjusting for conventional cardiovascular risk factors; hazard ratio 2.5 (0.9-6.8; p = 0.071) compared to patients with normal heart rate variability. Likewise, prolonged QTc interval was associated with premature death with an adjusted hazard ratio of 2.3 (1.3-4.0; p = 0.005). In a combined analysis, patients with abnormal values for heart rate variability and QTc had a poorer prognosis compared to patients with normal test values for both parameters (adjusted hazard ratio 6.7 (1.8-25; p = 0.005)). Of the 34 patients with both test values abnormal, 15 died and 14 of these from cardiovascular causes.

CONCLUSIONS

We conclude that combined abnormality in heart rate variability and QTc is a strong predictor of mortality in type 1 diabetes independently of conventional risk factors. These results have implications for future screening and treatment programmes for cardiovascular disease in type 1 diabetes.

Cardiovascular autonomic dysfunction predicts acute ischaemic stroke in patients with Type 2 diabetes mellitus: a 7-year follow-up study

AIMS

We investigated whether cardiovascular autonomic neuropathy (CAN) is associated with acute ischaemic stroke in patients with Type 2 diabetes.

METHODS

From 1999 to 2000, cardiovascular autonomic function tests were conducted in patients with Type 2 diabetes (n = 1458). Patients were followed up between 2006 and 2007. Standard tests for CAN measured heart rate variability parameters [expiration-to-inspiration (E/I) ratio, responses to the Valsalva manoeuvre and standing]. Using the American Diabetes Association criteria, the CAN scores were determined from the results of each test as follows: 0 = normal, 1 = abnormal (total maximum score 3). We assessed the development of acute ischaemic stroke events.

RESULTS

The prevalence of CAN at baseline was 55.7% (E/I 17.1%, Valsalva 39.4%, posture 27.3%) (n = 1126). During follow-up, 131 patients (11.6%) developed acute ischaemic stroke. The vascular events were more frequent in older patients (P < 0.001) and in those with diabetes of longer duration (P = 0.022), hypertension (P < 0.001) or diabetic retinopathy (P = 0.03) than in patients without vascular events. Patients with ischaemic stroke had higher creatinine levels (P = 0.045) and higher urine albumin excretion (P = 0.025) than those of patients without stroke. Cox proportional hazard regression analysis revealed that the CAN score was associated with the development of acute ischaemic stroke (total score 0 vs. 3, adjusted hazard ratio 2.7, 95% CI 1.3-5.5, P = 0.006).

CONCLUSION

Cardiovascular autonomic dysfunction was significantly associated with the development of ischaemic stroke in patients with Type 2 diabetes.

Effects of glucagon-like peptide-1, yohimbine, and nitrergic modulation on sympathetic and parasympathetic activity in humans

Glucagon-like peptide-1 (GLP-1), an incretin, which is used to treat diabetes mellitus in humans, inhibited vagal activity and activated nitrergic pathways. In rats, GLP-1 also increased sympathetic activity, heart rate, and blood pressure (BP). However, the effects of GLP-1 on sympathetic activity in humans are unknown. Our aims were to assess the effects of a GLP-1 agonist with or without alpha(2)-adrenergic or -nitrergic blockade on autonomic nervous functions in humans. In this double-blind study, 48 healthy volunteers were randomized to GLP-1-(7-36) amide, the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-l-arginine acetate (l-NMMA), the alpha(2)-adrenergic antagonist yohimbine, or placebo (i.e., saline), alone or in combination. Hemodynamic parameters, plasma catecholamines, and cardiac sympathetic and parasympathetic modulation were measured by spectral analysis of heart rate. Thereafter, the effects of GLP-1-(7-36) amide on muscle sympathetic nerve activity (MSNA) were assessed by microneurography in seven subjects. GLP-1 increased (P = 0.02) MSNA but did not affect cardiac sympathetic or parasympathetic indices, as assessed by spectral analysis. Yohimbine increased plasma catecholamines and the low-frequency (LF) component of heart rate power spectrum, suggesting increased cardiac sympathetic activity. l-NMMA increased the BP and reduced the heart rate but did not affect the balance between sympathetic and parasympathetic activity. GLP-1 increases skeletal muscle sympathetic nerve activity but does not appear to affect cardiac sympathetic or parasympathetic activity in humans.

The spectrum of diabetic neuropathies

Diabetes mellitus is associated with many different neuropathic syndromes, ranging from a mild sensory disturbance as can be seen in a diabetic sensorimotor polyneuropathy, to the debilitating pain and weakness of a diabetic lumbosacral radiculoplexus neuropathy. The etiology of these syndromes has been studied extensively, and may vary among metabolic, compressive, and immunological bases for the different disorders, as well as mechanisms yet to be discovered. Many of these disorders of nerve appear to be separate conditions with different underlying mechanisms, and some are caused directly by diabetes mellitus, whereas others are associated with it but not caused by hyperglycemia. This article discusses a number of the more common disorders of nerve found with diabetes mellitus. It discusses the symmetrical neuropathies, particularly generalized diabetic polyneuropathy, and then the focal or asymmetrical types of diabetes-associated neuropathy.

Neuropatia autonômica: uma complicação de alto risco no diabetes melito tipo 1

O acometimento patológico do sistema nervoso no diabetes melito é muito amplo e, freqüentemente, bastante grave. A prevalência de neuropatia diabética atinge níveis elevados com a evolução temporal do diabetes, chegando, geralmente, a freqüências acima de 50% de lesão neurológica em diferentes grupos de pacientes analisados em nosso meio e no exterior. A lesão neurológica nesta situação patológica é extensa no organismo humano diabético, envolvendo amplamente todo o sistema nervoso periférico nos seus componentes sensitivo-motor e autonômico: com clínica característica e concordante com as hipóteses patogênicas de natureza metabólica e/ou microvascular. O sistema nervoso autonômico é o elemento fundamental na regulação da função da maior parte dos sistemas ou órgãos no organismo, portanto, a sua lesão pode trazer importantes alterações para as funções cardiovascular, respiratória, digestiva, urinária e genital, podendo influir na função vital de alguns desses órgãos ou sistemas. Este artigo aborda as alterações decorrentes da lesão do sistema nervoso autonômico, especialmente nos pacientes diabéticos tipo 1, procurando dimensionar o risco de morbimortalidade.

Prediction of mortality using measures of cardiac autonomic dysfunction in the diabetic and nondiabetic population: the MONICA/KORA Augsburg Cohort Study

OBJECTIVES

To evaluate whether reduced heart rate variability (HRV), prolonged corrected QT (QTc) interval, or increased QT dispersion (QTD) are predictors of mortality in the general diabetic and nondiabetic population.

RESEARCH DESIGN AND METHODS

Nondiabetic (n = 1,560) and diabetic (n = 160) subjects aged 55-74 years were assessed to determine whether reduced HRV, prolonged QTc interval, and increased QTD may predict all-cause mortality. Lowest quartiles for the maximum-minimum R-R interval difference (max-min, as measured at baseline from a 20-s standard 12-lead resting electrocardiogram without controlling for depth and rate of respiration), QTc >440 ms and QTD >60 ms, were used as cutpoints.

RESULTS

During a 9-year follow-up, 10.5% of the nondiabetic and 30.6% of the diabetic population deceased. In the nondiabetic individuals, multivariate Cox proportional hazard models adjusted for cardiovascular risk factors and demographic variables showed that prolonged QTc interval (hazard ratio 2.02 [95% CI 1.29-3.17]; P = 0.002) but not low max-min (0.93 [0.65-1.34]; P = 0.700), and increased QTD (0.98 [0.60-1.60]; P = 0.939) were associated with increased mortality. In the diabetic subjects, prolonged QTc was also a predictor of mortality (3.00 [1.34-6.71]; P = 0.007), while a trend for an increased risk was noted in those with low max-min (1.74 [0.95-3.18]; P = 0.075), whereas increased QTD did not predict mortality (0.42 [0.06-3.16]; P = 0.402).

CONCLUSIONS

Prolonged QTc interval, but not increased QTD, is an independent predictor of a twofold and threefold increased risk of mortality in the nondiabetic and diabetic elderly general population, respectively. Low HRV during spontaneous breathing tends to be associated with excess mortality in the diabetic but not nondiabetic population.