Progression of cardiovascular autonomic dysfunction in patients with type 2 diabetes: a 7-year follow-up study

Intensive Glycemic Treatment Mitigates Cardiovascular and Mortality Risk Associated With Cardiac Autonomic Neuropathy in Type 2 Diabetes

BACKGROUND

Hyperglycemia is one of the proposed risk factors for cardiac autonomic neuropathy (CAN). CAN is associated with increased cardiovascular and mortality risk. But it remains unclear whether cardiovascular and mortality risk associated with CAN is mitigated by intensive glycemic treatment.

METHODS AND RESULTS

This secondary analysis included 7866 patients from the ACCORDION (Action to Control Cardiovascular Risk in Diabetes Follow-On) study. CAN was defined using ECG-derived measures. End points included primary outcome (composite of cardiovascular events) and total deaths. During a median follow-up of 8.9 years, a total of 1341 cardiovascular events and 1364 all-cause deaths were ascertained. Compared with standard treatment, intensive treatment reduced risk of primary outcome and total deaths among patients with CAN but not among those without CAN. Compared with absence of CAN, the presence of CAN was associated with increased risk of primary outcome and total deaths in the standard group but not in the intensive group. Significant interactions were found between CAN status and treatment arms on risk of primary outcome and total deaths. Incidence rates per 100 person-years of primary outcome and total deaths were similar between patients without CAN and those with CAN undergoing intensive treatment.

CONCLUSIONS

Intensive glycemic treatment mitigates cardiovascular and mortality risk associated with CAN and may serve as an effective way in the management of CAN.

Heart rate variability tests for diagnosing cardiovascular autonomic neuropathy in patients with type 2 diabetes mellitus in advanced stages of kidney disease

Cardiovascular Autonomic Neuropathy (CAN) is one of the most devastating complications of Diabetes Mellitus (DM) and presents high morbidity and mortality. Its association with diabetic kidney disease (DKD) worsens the condition even further. CAN diagnosis remains a challenge and is being based on reflex tests which are laborious, risky and difficult to perform. Heart Rate Variability (HRV) tests has been suggested as having high utility in diagnosing CAN, but this issue remains controversial. The aim is to evaluate the sensitivity and specificity of HRV tests to diagnose CAN in patients with type 2 diabetes mellitus (T2DM) and DKD with severely increased albuminuria. This is a cross-sectional study in patients with T2DM and DKD with severely increased albuminuria. A total of 48 subjects were recruited and underwent laboratory and neuropathy assessment. The diagnosis of CAN was first confirmed in 75% (36/48) of patients based on cardiovascular autonomic reflex tests (CARTs). HRV tests (VLF, LF, TP and SDNN) differed between groups with and without CAN (212 vs. 522 ms2, p = 0.024; 57 vs. 332 ms2, p = 0.025; 359.5 vs. 2733 ms2, p = 0.007; 20 vs. 48 ms, p = 0.012), respectively. The best cut-off points based on ROC curve were < 1,117 ms2, < 152.5 ms2, < 1,891 ms2 and < 46.5 ms, respectively. VLF and TP reached highest sensitivity values (97% and 92%) and F1 Score of 90%, while LF had best specificity (75%) and TP had best accuracy (85%). Our best model of serial algorithm using VLF as first screening test and TP in sequency obtained a sensitivity of 97% and accuracy of 90%, reducing in 90% the need to perform CARTs. Our findings suggest that it is possible to achieve high sensitivity and accuracy using an algorithm with VLF and TP parameters analyzed in series. It could enable a simpler and early diagnosis, avoiding CARTs complications.

A higher resting heart rate is associated with cardiovascular event risk in patients with type 2 diabetes mellitus without known cardiovascular disease

A higher resting heart rate (RHR) is associated with an increased risk of cardiovascular events in patients with type 2 diabetes mellitus (T2DM) and cardiovascular diseases. The aim of this study was to investigate the association between RHR and cardiovascular events in T2DM patients with diabetic retinopathy and without known cardiovascular disease. We analyzed the association between RHR and cardiovascular events, including coronary, cerebral, renal and vascular events or cardiovascular death in T2DM patients with retinopathy and hyperlipidemia without prior cardiovascular events who were enrolled in the EMPATHY study. Data from 4746 patients were analyzed. The median RHR was 76 bpm. Patients were divided into four groups based on their baseline RHR ( < 60, 60-69, 70-79, and ≥80 bpm). Patients with a higher RHR were more likely to be younger and had a higher body mass index, blood pressure value, HbA1c value, and estimated glomerular filtration rate and a lower B-type natriuretic peptide value; they also had a higher proportion of current smoking status, neuropathy, and nephropathy. After adjusting for confounders, including the aforementioned risk factors, a RHR of 70-79 bpm and a RHR ≥ 80 bpm were significantly associated with cardiovascular events (hazard ratio 1.50, 95% CI 1.03-2.20; and hazard ratio 1.62, 95% CI 1.11-2.36; respectively) compared to a RHR of 60-69 bpm. The analysis using restricted cubic splines indicated that the cardiovascular risk seemed to be similarly high when the RHR range was ≥70 bpm. In conclusion, in T2DM patients with diabetic retinopathy and without known cardiovascular disease, a high RHR, particularly ≥70 bpm, was associated with the risk of cardiovascular events compared to a RHR of 60-69 bpm. High resting heart rate (RHR), particularly ≥70 bpm, was associated with the risk of cardiovascular events compared to RHR 60-69 bpm in patients with type 2 diabetes mellitus (T2DM), diabetic retinopathy, and hyperlipidemia, but without known cardiovascular disease.

The Role of Angiotensin Receptor Blockers in the Personalized Management of Diabetic Neuropathy

Neuropathy is a frequent complication of diabetes mellitus (DM) and is associated with the increased risk ofamputation and vascular events. Tight glycemic control is an important component inthe prevention of diabetic neuropathy. However, accumulating data suggest that angiotensin receptor blockers (ARBs) might also be useful in this setting. We discuss the findings of both experimental and clinical studies that evaluated the effects of ARBs on indices of diabetic neuropathy. We also review the implicated mechanisms of the neuroprotective actions of these agents. Overall, it appears that ARBs might be a helpful tool for preventing and delaying the progression of diabetic neuropathy, but more data are needed to clarify their role in the management of this overlooked complication of DM.

Orthostatic blood pressure changes and diabetes duration

To determine the prevalence and the associated clinical characteristics of orthostatic hypotension and orthostatic hypertension in patients with diabetic sensorimotor polyneuropathy (DSP).

METHODS

A single-center retrospective cross-sectional study was conducted on 200 DSP patients who had 3-minute orthostatic measures as part of the standard clinic evaluation. We measured the heart rate (HR) and blood pressure (BP) supine and again after 3 min of standing.

RESULTS

The prevalence of orthostatic hypotension was 19.5% and that of orthostatic hypertension was 23%. Subjects with orthostatic hypotension had significantly longer diabetes duration than subjects who were normotensive and those with orthostatic hypertension. Quantitatively, BP changes from supine to standing correlated with diabetes duration (R = 0.306; P = 0.0582) and age (R = 0.434; P = 0.006) in subjects with orthostatic hypotension.

CONCLUSIONS

Orthostatic hypertension and orthostatic hypotension are frequent in patients with DSP. Orthostatic hypertension is associated with shorter diabetes duration than orthostatic hypotension.

Prevalence and Correlates of Cardiovascular Autonomic Neuropathy Among Patients with Diabetes in Uganda: A Hospital-Based Cross-sectional Study

Background

Cardiovascular autonomic neuropathy (CAN) is a common complication in individuals with diabetes mellitus (DM) but often overlooked in clinical practice. The burden and correlates of CAN have not been extensively studied in low-income countries, particularly in sub-Saharan Africa.

Objectives

To determine the prevalence and correlates of CAN among adults in ambulatory diabetes care in southwestern Uganda.

Method

We conducted a cross-sectional study among adults with diabetes from November 2018 to April 2019. CAN was assessed using the five autonomic function tests: deep breathing, Valsalva maneuver, postural index on standing, change in blood pressure during standing and diastolic blood pressure response to isometric exercise. We estimated the prevalence of CAN and fit regression models to identify its demographic and clinical correlates.

Results

We enrolled 299 individuals. The mean age was 50.1 years (SD ± 9.8), mean HbA1c was 9.7 (SD ± 2.6) and 69.6% were female. CAN was detected in 156/299 (52.2%) of the participants on the basis of one or more abnormal cardiovascular autonomic reflex tests. Out of 299 participants, 88 (29.4%) were classified as early CAN while 61/299 (20.4%) and 7/299 (2.3%) were classified as definite and severe (advanced) CAN respectively. In multivariable regression models, age over 50 years (aOR 3.48, 95%CI 1.35 -8.99, p = 0.010), duration of diabetes over 10 years (aOR 4.09, 95%CI 1.78 -9.38, p = 0.001), and presence of diabetic retinopathy (aOR 2.25, 95%CI 1.16 -4.34, p = 0.016) were correlated with CAN.

Conclusions

Our findings reveal a high prevalence of CAN among individuals in routine outpatient care for diabetes mellitus in Uganda. Older age, longer duration of diabetes and coexistence of retinopathy are associated with CAN. Future work should explore the clinical significance and long term outcomes associated with CAN in this region.

Cardiovascular Autonomic Neuropathy and Distal Symmetric Sensorimotor Polyneuropathy: These Two Diabetic Microvascular Complications do not Invariably Co-Exist

Background:

Cardiovascular autonomic neuropathy (CAN) and distal symmetrical sensorimotor polyneuropathy (DSPN) are serious microvascular complications of diabetes mellitus (DM). Their simultaneous development remains disputable. The aim of the present study was to examine the correlation between CAN and the presence/severity of DSPN in DM.

Methods:

Subjects with type 1 (group A: n=51; mean age 40.4 years) and type 2 DM (group B: n=153; mean age 64.6 years) were studied. Evaluation of DSPN was based on neuropathy disability score. Assessment of CAN was based on the battery of 4 standardized cardiovascular autonomic function tests.

Results:

In group A, patients with moderate/severe DSPN exhibited a 12-fold higher likelihood of CAN in univariate analysis (p=0.035). However, significance was lost after adjustment for gender, age, DM duration, and haemoglobin A1c. In group A, likelihood for CAN did not correlate with the presence of mild DSPN in univariate and multivariate analysis. In group B, likelihood of CAN was similar in patients with mild and in those with moderate/severe DSPN compared with patients without DSPN in univariate and multivariate analysis. In between group comparison CAN was similarly distributed in the 2 groups (p for interaction=0.367), in patients with no, mild and moderate/severe DSPN.

Conclusion:

CAN does not always co-exist with degrees of DSPN, ranging from mild to moderate/ severe and is similarly distributed in T1DM and T2DM patients with mild and moderate/severe DSPN and in patients without DSPN.

Clinical factors associated with the recovery of cardiovascular autonomic neuropathy in patients with type 2 diabetes mellitus

Background

Cardiovascular autonomic neuropathy (CAN) is a major cause of morbidity and mortality in diabetes patients. Although several risk factors for CAN progression have been established, whether CAN is reversible remains unclear and the clinical factors associated with CAN recovery have not been identified. This study aimed to determine clinical factors related to CAN recovery.

Methods

Type 2 diabetes patients with CAN but free of cardiovascular disease at baseline were enrolled and followed for 2–3 years in this retrospective longitudinal study. CAN was classified as early (one abnormal parasympathetic test), definite (two or more abnormal parasympathetic tests), severe (definite plus orthostatic hypotension), or atypical (early plus orthostatic hypotension or orthostatic hypotension alone) based on Ewing’s method. CAN recovery was classified as partial or complete: Partial recovery was defined as one-step improvement in CAN stage (early to normal, definite to early, or severe to definite), including the disappearance of only one abnormal result in any stage. Complete recovery was defined as normalization from definite or severe CAN.

Results

Among 759 subjects with CAN, 29.9% (n = 227) experienced CAN recovery, and 1.2% (n = 9) recovered completely. In a multivariate model, younger age (odds ratio [OR] per 5-year decrease 1.49; 95% confidence interval [CI] 1.25–1.78, P < 0.001), shorter duration of diabetes (OR per 5-year decrease 1.33; 95% CI 1.05–1.67, P = 0.016), presence of micro/macroalbuminuria (OR 0.34; 95% CI 0.15–0.78, P = 0.011), body weight reduction (OR per 1-kg decrease 1.11; 95% CI 1.02–1.21, P = 0.016), and HbA1c reduction (OR per 1% decrease 1.32; 95% CI 1.05–1.67, P = 0.019) were significantly associated with composite events of partial and complete CAN recovery. Age had the highest relative significance among the associated clinical factors. In addition, younger age was the only significant factor in complete CAN recovery.

Conclusions

Younger age was the most important factor in CAN recovery in subjects with type 2 diabetes, including recovery from the definite or severe stage. HbA1c reduction, body weight reduction, no concurrent micro/macroalbuminuria, and shorter duration of diabetes were also significantly associated with CAN recovery.

Electronic supplementary material

The online version of this article (10.1186/s12933-019-0830-4) contains supplementary material, which is available to authorized users.

Microvascular Parameters Help to Predict Stroke Risk in the Asian Diabetic Population in Taiwan: A Population Based Case-Control Study

Intensive glycemic control has not shown consistent findings in stroke prevention for diabetes patients, particularly for those with microvascular complications. This case-control study evaluates the risks of stroke in Asian diabetic population with microvascular complications. From the insurance claims of Taiwan, we identified 67,426 type 2 diabetic mellitus (DM) patients with newly diagnosed stroke in 2000–2011 and 134,852 randomly selected controls with DM but without stroke, matched by sex, age, and number of years since diagnosis of DM. Conditional logistic regression analysis measured crude odds ratios (OR) and adjusted odds ratio (aOR) of stroke and 95% confidence intervals (CI) for associations with demographic status, comorbidities, and microvascular complications: retinopathy (RetP), neuropathy (NeuP) or nephropathy (NepP). The aOR of stroke increased significantly associated with each complication: 1.47 with RetP, 1.73 with NeuP and 1.23 with NepP. The risk increased further when there was a combination of complications. The overall aOR of stroke was 2.83 (95% CI 2.58–3.09) for stroke patients with 3 microvascular complications. The corresponding aOR of ischemic stroke was 2.64 (95% CI 2.39–2.91) and that of hemorrhagic stroke was 4.12 (95% CI 3.25–5.22). The number of microvascular complications positively correlated to the prevalence of comorbidity (p < 0.01). This study suggests that microvascular complications are significant stroke predictors, with a greater involvement for ischemic stroke than for hemorrhagic stroke. Multiple microvascular complications interactively increase the stroke risk. Our study contributes to the identification of high-risk subjects for stroke prevention and adequate glycemic control.

Assessment of Cardiac Autonomic Function by Post Exercise Heart Rate Recovery in Diabetics

Background and Aims: Autonomic dysfunction in type 2 diabetes mellitus (DM) patients may translate into an increased cardiovascular morbidity and mortality. Autonomic system regulates ‘heart rate recovery’ (HRR), an important predictor of cardiovascular mortality, which can be assessed using the exercise electrocardiogram (ECG). Hence, utilizing HRR, this study assessed the autonomic function of the cardiovascular system after one minute of exercise stress test in both, patients with and without type 2 DM.

Materials and Methods: A prospective case control study involving 50 patients with type 2 DM and 50 without type 2 DM, matched for age and sex, was carried out. Each subject underwent an exercise stress test by treadmill using the Bruce protocol. Cardiovascular parameters like heart rate was recorded using a 12 lead ECG along with blood pressure.

Results: Patients with T2DM had lesser HRR after exercise (p < 0.001). Exercise capacity was significantly reduced among patients with T2DM when compared to controls (p = 0.01). A multiple linear regression analysis (R2=0.26) revealed that duration of diabetes (β=−0.02, p=0.048) and resting systolic blood pressure (SBP) (β=−010, p=0.048) are independent predictors of HRR.

Conclusion: The study revealed HRR to be significantly reduced among patients with type 2 DM. HRR may hint at the presence of cardiac autonomic dysfunction and predict the cardiovascular mortality.

Cardiac autonomic neuropathy in patients with diabetes mellitus: current perspectives

Cardiac autonomic neuropathy (CAN) is a common and often-underdiagnosed complication of diabetes mellitus (DM). CAN is associated with increased mortality, cardiovascular disease, chronic kidney disease, and morbidity in patients with DM, but despite these significant consequences CAN often remains undiagnosed for a prolonged period. This is commonly due to the disease being asymptomatic until the later stages, as well as a lack of easily available screening strategies. In this article, we review the latest developments in the epidemiology, pathogenesis, diagnosis, consequences, and treatments of CAN in patients with DM.

Hemoglobin A1c levels and risk of sudden cardiac death: A nested case-control study

BACKGROUND

Sudden cardiac death (SCD) is often the first manifestation of cardiovascular disease (CVD), and preventive strategies within this broad population are lacking. Patients with diabetes represent a high-risk subgroup, but few data exist regarding whether measures of glycemia mediate risk and/or add to SCD risk stratification.

OBJECTIVE

The purpose of this study was to examine the association between hemoglobin A1c (HbA1c) and SCD.

METHODS

We performed a case-control analysis among individuals enrolled in 6 prospective cohort studies. HbA1c levels were determined for 482 cases of SCD and 914 matched controls. Conditional logistic regression with fixed effects meta-analysis was used for analysis.

RESULTS

In multivariable models, HbA1c levels were linearly associated with SCD risk over follow-up of 11.3 years (P <.001). Each 1% increment in HbA1c was associated with a hazard ratio (HR) of 1.32 (95% confidence interval [CI] 1.16-1.50). The magnitude of the association was greater in subjects without vs those with known CVD [HR per 1% increment 1.64 (95% CI 1.31-2.06) vs 1.15 (95% CI 0.99-1.33), P interaction = .009]. In models simultaneously controlling for diabetes status and HbA1c, the association between HbA1c and SCD remained significant (HR 1.29, 95% CI 1.07-1.55, P = .01), whereas the association between diabetes and SCD was attenuated (relative risk 1.21, 95% CI 0.64-2.27, P = .56).

CONCLUSION

In these prospective cohorts, HbA1c levels associated with SCD risk, particularly among those without known CVD, even after controlling for diabetes status. These data support the hypothesis that hyperglycemia mediates SCD risk among patients with diabetes.

Morphologic Changes in Autonomic Nerves in Diabetic Autonomic Neuropathy

Diabetic neuropathy is one of the major complications of diabetes, and it increases morbidity and mortality in patients with both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Because the autonomic nervous system, for example, parasympathetic axons, has a diffuse and wide distribution, we do not know the morphological changes that occur in autonomic neural control and their exact mechanisms in diabetic patients with diabetic autonomic neuropathy (DAN). Although the prevalence of sympathetic and parasympathetic neuropathy is similar in T1DM versus T2DM patients, sympathetic nerve function correlates with parasympathetic neuropathy only in T1DM patients. The explanation for these discrepancies might be that parasympathetic nerve function was more severely affected among T2DM patients. As parasympathetic nerve damage seems to be more advanced than sympathetic nerve damage, it might be that parasympathetic neuropathy precedes sympathetic neuropathy in T2DM, which was Ewing's concept. This could be explained by the intrinsic morphologic difference. Therefore, the morphological changes in the sympathetic and parasympathetic nerves of involved organs in T1DM and T2DM patients who have DAN should be evaluated. In this review, evaluation methods for morphological changes in the epidermal nerves of skin, and the intrinsic nerves of the stomach will be discussed.

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.

Cardiovascular autonomic dysfunction predicts severe hypoglycemia in patients with type 2 diabetes: a 10-year follow-up study

OBJECTIVE The aim of this study was to investigate the development of severe hypoglycemia (SH) in the presence of cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS From January 2001 to December 2002, a total of 894 patients with type 2 diabetes were enrolled. A cardiovascular autonomic function test (AFT) was performed using the following heart rate variability parameters: expiration-to-inspiration ratio, response to Valsalva maneuver, and standing. From the results for each of the three tests (0 for normal, 1 for abnormal), a total AFT score of 1 was defined as early CAN, and an AFT score of ≥2 was defined as definite CAN. RESULTS The median follow-up time was 9.5 years. The mean age was 54.5 ± 10.1 years, and the mean duration of diabetes was 8.9 ± 6.3 years. One hundred ninety-six patients (31.4%) showed an abnormal cardiovascular AFT score at baseline. Sixty-two patients (9.9%) experienced 77 episodes of SH (1.33 per 100 patient-years). The number of SH events increased as the CAN score increased (23 patients [5.4%] with normal score; 17 patients [17.2%] with early CAN; and 22 patients [22.7%] with definite CAN; P for trends < 0.001). Cox proportional hazards regression analysis revealed that SH was associated with definite CAN (normal vs. definite CAN: hazard ratio 2.43 [95% CI 1.21-4.84]; P = 0.012). CONCLUSIONS Definite CAN was an independent prognostic factor for the development of SH in patients with type 2 diabetes.

Diabetic cardiovascular autonomic neuropathy: clinical implications

Diabetic cardiovascular autonomic neuropathy (DCAN), the impairment of the autonomic balance of the cardiovascular system in the setting of diabetes mellitus (DM), is frequently observed in both Type 1 and 2 DM, has detrimental effects on the quality of life and portends increased mortality. Clinical manifestations include: resting heart rate disorders, exercise intolerance, intraoperative cardiovascular lability, orthostatic alterations in heart rate and blood pressure, QT-interval prolongation, abnormal diurnal and nocturnal blood pressure variation, silent myocardial ischemia and diabetic cardiomyopathy. Clinical tests for autonomic nervous system evaluation, heart rate variability analysis, autonomic innervation imaging techniques, microneurography and baroreflex analysis are the main diagnostic tools for DCAN detection. Aldose reductase inhibitors and antioxidants may be helpful in DCAN therapy, but a regular, more generalized and multifactorial approach should be adopted with inclusion of lifestyle modifications, strict glycemic control and treatment of concomitant traditional cardiovascular risk factors, in order to achieve the best therapeutic results. In the present review, the authors provide aspects of DCAN pathophysiology, clinical presentation, diagnosis and an algorithm regarding the evaluation and management of DCAN in DM patients.

Heart rate variability and plasma norepinephrine concentration in diabetic dogs at rest

Cardiac autonomic neuropathy in dogs with diabetic mellitus (DM) was evaluated using measurement of heart rate variability (HRV) and plasma norepinephrine (NE) concentration. Dogs were divided into 2 groups; the control non-DM group (n = 13) and the diabetic group (n = 22) which was further divided into the well-controlled DM (n = 11) and the poorly-controlled DM subgroups (n = 11) according to their fasting plasma fructosamine concentrations. The electrocardiogram (ECG) was recorded continuously for at least 30 min to yield HRV. The results showed that in the poorly-controlled DM subgroup, the average of normal R-R interval (mean N-N), SD of the mean of all 5-min segments of normal RR intervals (SDANN) were lower than the control group while heart rate was higher (P < 0.05). The NNA, SDNN, SDNN index and pNN50% were significantly lower when compared with the well-controlled DM subgroup (P < 0.05). The high frequency (HF) and total power were significantly lower while the ratio of low to high frequency (LF/HF) was higher (P < 0.05) when compared with the well-controlled DM subgroup. Moreover, in the poorly-controlled DM subgroup, plasma NE concentration was lower than the control group (210 ± 37 vs. 479 ± 74 pg/ml, P < 0.05). There was a significantly negative correlation between plasma NE and plasma fructosamine concentrations. It is concluded that cardiac autonomic neuropathy occurred in poorly-controlled DM dogs. The sympathetic activity was suppressed as shown by decrease in both plasma NE concentration and LF component.

Association of serum adipocytokine levels with cardiac autonomic neuropathy in type 2 diabetic patients

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a common complication of diabetes associated with poor prognosis. In addition, the autonomic imbalance is associated with cardiovascular disease (CVD) in diabetes. It is thought that adipocytokines contribute to the increased risk of vascular complications in patients with type 2 diabetes mellitus (T2DM). However, literature data on the association between CAN with adipocytokines such as leptin, tumor necrosis factor-alpha (TNF-alpha), adiponectin in subjects with T2DM is limited.Therefore, in the present study, we examined the relationship between fasting serum leptin, TNF- alpha and adiponectin and CAN in Korean T2DM patients.

METHODS

A total of 142 T2DM patients (94 males, 48 females) were recruited. CAN was assessed by the five tests according to the Ewing's protocol and the time and frequency domain of the heart rate variability (HRV) was evaluated. Serum TNF-alpha and adiponectin levels were measured using enzyme-linked immunosorbent assay and serum leptin levels were measured using radioimmunoassay.

RESULTS

Although, the mean levels of leptin, TNF-alpha and adiponectin were not significantly different between the groups with and without CAN, the levels of leptin and adiponectin had a tendency to increase as the score of CAN increased (p = 0.05, p = 0.036). Serum leptin levels demonstrated a negative correlation with low frequency (LF) in the upright position (p = 0.037). Regarding TNF-alpha, a significant negative correlation was observed with SDNN and RMSSD in the upright position (p = 0.023, p = 0.019). Adiponectin levels were not related to any HRV parameters. Multivariate logistic regression analysis demonstrated that the odds of CAN increased with a longer duration of diabetes (1.25, [1.07-1.47]) and higher homeostatic model of assessment-insulin resistance (HOMA-IR) (5.47, [1.8-16.5]). The relative risks for the presence of CAN were 14.1 and 51.6 for the adiponectin 2nd, 3rd tertiles when compared with first tertile (p-value for trend = 0.022).

CONCLUSIONS

In the present study, the higher serum adiponectin levels and HOMA-IR were associated with an increased risk for the presence of CAN. Also, the CAN score correlated with the serum adiponectin. Serum adipocytokines such as leptin and TNF-alpha were significantly correlated with parameters of HRV, representative markers of CAN. Future prospective studies with larger number of patients are required to establish a direct relationship between plasma adipocytokine concentrations and the development or severity of CAN.

Cardiovascular autonomic neuropathies as complications of diabetes mellitus

Diabetic autonomic neuropathies are a heterogeneous and progressive disease entity and commonly complicate both type 1 and type 2 diabetes mellitus. Although the aetiology is not entirely understood, hyperglycaemia, insulin deficiency, metabolic derangements and potentially autoimmune mechanisms are thought to play an important role. A subgroup of diabetic autonomic neuropathy, cardiovascular autonomic neuropathy (CAN), is one of the most common diabetes-associated complications and is ultimately clinically important because of its correlation with increased mortality. The natural history of CAN is unclear, but is thought to progress from a subclinical stage characterized by impaired baroreflex sensitivity and abnormalities of spectral analysis of heart rate variability to a clinically apparent stage with diverse and disabling symptoms. Early diagnosis of CAN, using spectral analysis of heart rate variability or scintigraphic imaging techniques, might enable identification of patients at highest risk for the development of clinical CAN and, thereby, enable the targeting of intensive therapeutic approaches. This Review discusses methods for diagnosis, epidemiology, natural history and potential causes and consequences of CAN.

Cardiovascular autonomic neuropathy in diabetes: clinical impact, assessment, diagnosis, and management

The Cardiovascular Autonomic Neuropathy (CAN) Subcommittee of the Toronto Consensus Panel on Diabetic Neuropathy worked to update CAN guidelines, with regard to epidemiology, clinical impact, diagnosis, usefulness of CAN testing, and management. CAN is the impairment of cardiovascular autonomic control in the setting of diabetes after exclusion of other causes. The prevalence of confirmed CAN is around 20%, and increases up to 65% with age and diabetes duration. Established risk factors for CAN are glycaemic control in type 1 and a combination of hypertension, dyslipidaemia, obesity, and glycaemic control in type 2 diabetes. CAN is a risk marker of mortality and cardiovascular morbidity, and possibly a progression promoter of diabetic nephropathy. Criteria for CAN diagnosis and staging are: (1) one abnormal cardiovagal test result identifies possible or early CAN; (2) at least two abnormal cardiovagal test results are required for definite or confirmed CAN; and (3) the presence of orthostatic hypotension in addition to abnormal heart rate test results identifies severe or advanced CAN. Progressive stages of CAN are associated with increasingly worse prognosis. CAN assessment is relevant in clinical practice for (1) diagnosis of CAN clinical forms, (2) detection and tailored treatment of CAN clinical correlates (e.g. tachycardia, orthostatic hypotension, non-dipping, QT interval prolongation), (3) risk stratification for diabetic complications and cardiovascular morbidity and mortality, and (4) modulation of targets of diabetes therapy. Evidence on the cost-effectiveness of CAN testing is lacking. Apart from the preventive role of intensive glycaemic control in type 1 diabetes, recommendations cannot be made for most therapeutic approaches to CAN.

Somatic DNA damages in cardiovascular autonomic neuropathy

Cardiovascular autonomic neuropathy (CAN) is one of the most clinically significant complications of diabetes mellitus. Even though many ethological factors have been attributed for the pathogenesis of this disease no attempts were made to correlate DNA damage as a causative factor. Hence the present study was undertaken to asses the extent of somatic DNA damages by cytokinesis-block micronuclei assay (CBMN). An attempt is also being made to correlate the habits and/or risk factors and socioeconomic status with CAN. The CBMN frequency of 46 patients suffering from autonomic neuropathy was compared with that of 25 healthy age and sex matched controls. All the subjects were suffering from type 2 diabetes for at least 8 years and have varying degrees of coronary artery diseases. The mean CBMN frequency of the patients was statistically higher than that of the healthy control subjects (P < 0.05). The CBMN frequency was found to be significantly altered in CAN patients who where physical inactivity and smoking. A significant correlation could also be observed between CAN and smoking, diabetes mellitus, hypertension, dyslipidemia, abdominal obesity, and physical activity.

Early progression of the autonomic dysfunction observed in pediatric type 1 diabetes mellitus

To focus on early cardiac and vascular autonomic dysfunction that might complicate type 1 diabetes mellitus in children, we planned an observational, cross-sectional study in a population of 93 young patients, under insulin treatment, subdivided in 2 age subgroups (children: 11.5+/-0.4 years; adolescents: 19.3+/-0.2 years). Time and frequency domain analysis of RR interval and systolic arterial pressure variability provided quantitative indices of the sympatho-vagal balance regulating the heart period, of the gain of cardiac baroreflex, and of the sympathetic vasomotor control. Sixty-eight children of comparable age served as a reference group. At rest, systolic arterial pressure and the power of its low-frequency component were greater in patients than in controls, particularly in children (14.0+/-2.3 versus 3.1+/-0.3 mm Hg2). Moreover, baroreflex gain was significantly reduced in both subgroups of patients. Standing induced similar changes in the autonomic profiles of controls and patients. A repeat study after 1 year showed a progression in low-frequency oscillations of arterial pressure and a shift toward low frequency in RR variability. Data in young patients with type 1 diabetes mellitus show a significant increase in arterial pressure, a reduced gain of the baroreflex regulation of the heart period, and an increase of the low-frequency component of systolic arterial pressure variability, suggestive of simultaneous impairment of vagal cardiac control and increases of sympathetic vasomotor regulation. A repeat study after 1 year shows a further increase of sympathetic cardiac and vascular modulation, suggesting early progression of the autonomic dysfunction.