Left ventricular dysfunction in normotensive Type 1 diabetic patients: the impact of autonomic neuropathy

Role of purinergic receptors in cardiac sympathetic nerve injury in diabetes mellitus

Diabetic cardiac autonomic neuropathy is a common and serious chronic complication of diabetes, which can lead to sympathetic and parasympathetic nerve imbalance and a relative excitation of the sympathetic nerve. Purinergic receptors play a crucial role in this process. Diabetic cardiac sympathetic nerve injury affects the expression of purinergic receptors, and activated purinergic receptors affect the phosphorylation of different signaling pathways and the regulation of inflammatory processes. This paper introduces the abnormal changes of sympathetic nerve in diabetes mellitus and summarizes the recently published studies on the role of several purinergic receptor subtypes in diabetic cardiac sympathetic nerve injury. These studies suggest that purinergic receptors as novel drug targets are of great significance for the treatment of diabetic autonomic neuropathy. This article is part of the Special Issue on "Purinergic Signaling: 50 years".

Detecting and treating the protean manifestations of diabetic autonomic neuropathy

The manifestations of diabetic autonomic neuropathy (DAN) are protean and clinically involve multiple systems, including the cardiovascular system, the gastrointestinal system, the genitourinary system as well as the sweat glands (sudomotor dysfunction) and the gallbladder. In addition, cardiac autonomic neuropathy (CAN) is associated with a correctible inability to appreciate and correct hypoglycaemia. While not a clinical problem, pupillary involvement should be the clue and the catalyst to investigate for other manifestations of DAN. This review outlines a practical approach to detecting and investigating the manifestations of DAN. Of particular importance is early detection of cardiovascular involvement where prompt therapy through glycaemic control can decrease the severity of CAN and decelerate the frequency and severity of retinopathy and nephropathy in addition to decreasing cardiovascular events and mortality. CAN also plays a role in accelerating other diabetic complications such as acute ischaemic stroke, heart failure, medial artery calcinosis, foot ulcers, peripheral artery disease and Charcot joints. Many therapies of DAN are available, which should not only decrease morbidity and mortality from DAN, but also improve the patient's quality of life. However, the therapies available are largely symptomatic.

Role of peripheral 5-HT5A receptors in 5-HT-induced cardiac sympatho-inhibition in type 1 diabetic rats

5-HT inhibits cardiac sympathetic neurotransmission in normoglycaemic rats, via 5-HT1B, 5-HT1Dand 5-HT5Areceptor activation. Since type 1 diabetes impairs the cardiac sympathetic innervation leading to cardiopathies, this study aimed to investigate whether the serotonergic influence on cardiac noradrenergic control is altered in type 1 diabetic rats. Diabetes was induced in male Wistar rats by streptozotocin (50 mg/kg, i.p.). Four weeks later, the rats were anaesthetized, pithed and prepared for producing tachycardic responses by electrical preganglionic stimulation (C7-T1) of the cardioaccelerator sympathetic outflow or i.v. noradrenaline bolus injections. Immunohistochemistry was performed to study 5-HT1B, 5-HT1Dand 5-HT5Areceptor expression in the stellate ganglion from normoglycaemic and diabetic rats. In the diabetic group, i) i.v. continuous infusions of 5-HT induced a cardiac sympatho-inhibition that was mimicked by the 5-HT1/5Aagonist 5-carboxamidotryptamine (without modifying noradrenaline-induced tachycardia), but not by the agonists indorenate (5-HT1A), CP 93,129 (5-HT1B), PNU 142633 (5-HT1D), or LY344864 (5-HT1F); ii) SB 699551 (5-HT5Aantagonist; i.v.) completely reversed 5-CT-induced cardiac sympatho-inhibition; and iii) 5-HT5Areceptors were more expressed in the stellate ganglion compared to normoglycaemic rats. These results show the prominent role of the peripheral 5-HT5Areceptors prejunctionally inhibiting the cardiac sympathetic drive in type 1 diabetic rats.

Role of peripheral 5-HT5A receptors in 5-HT-induced cardiac sympatho-inhibition in type 1 diabetic rats

5-HT inhibits cardiac sympathetic neurotransmission in normoglycaemic rats, via 5-HT_1B, 5-HT_1D and 5-HT_5A receptor activation. Since type 1 diabetes impairs the cardiac sympathetic innervation leading to cardiopathies, this study aimed to investigate whether the serotonergic influence on cardiac noradrenergic control is altered in type 1 diabetic rats. Diabetes was induced in male Wistar rats by streptozotocin (50 mg/kg, i.p.). Four weeks later, the rats were anaesthetized, pithed and prepared for producing tachycardic responses by electrical preganglionic stimulation (C₇-T₁) of the cardioaccelerator sympathetic outflow or i.v. noradrenaline bolus injections. Immunohistochemistry was performed to study 5-HT_1B, 5-HT_1D and 5-HT_5A receptor expression in the stellate ganglion from normoglycaemic and diabetic rats. In the diabetic group, i) i.v. continuous infusions of 5-HT induced a cardiac sympatho-inhibition that was mimicked by the 5-HT_1/5A agonist 5-carboxamidotryptamine (without modifying noradrenaline-induced tachycardia), but not by the agonists indorenate (5-HT_1A), CP 93,129 (5-HT_1B), PNU 142633 (5-HT_1D), or LY344864 (5-HT_1F); ii) SB 699551 (5-HT_5A antagonist; i.v.) completely reversed 5-CT-induced cardiac sympatho-inhibition; and iii) 5-HT_5A receptors were more expressed in the stellate ganglion compared to normoglycaemic rats. These results show the prominent role of the peripheral 5-HT_5A receptors prejunctionally inhibiting the cardiac sympathetic drive in type 1 diabetic rats.

Baroreflex sensitivity with different lags and random forests for staging cardiovascular autonomic neuropathy in subjects with diabetes

Impaired baroreflex sensitivity (BRS) may indicate cardiovascular autonomic neuropathy (CAN), which often remains undiagnosed during the initial course of diabetes mellitus. The baroreflex mechanism can be considered negative feedback because of baroreflex delay, the time delay between a change in blood pressure and the counteracting heart rate response. This work sought to analyze BRS considering lags from 1 to 10 RR intervals. We hypothesized that diabetic patients with subclinical CAN (SCAN) have a detectable delay in autonomic nervous system activity and that this would differ from patients without CAN (NCAN) and with established CAN (ECAN). In the first stage, 30 patients were included in an exploratory analysis using the Principal Component Analysis. Six indexes related to the BRS delay were proposed and considered significant for staging diabetic patients. Three indexes allowed for the differentiating of patients with and without CAN, and three indexes distinguished subjects with SCAN from subjects with NCAN or ECAN. Then, in the second stage, a random forest model was developed with 72 subjects, using the variables selected in the first stage. It was possible to detect SCAN, and to point out those subjects with the potential to change the CAN stage, allowing for the tracking of CAN progression. The model achieved a sensitivity of 96% and specificity of 100% to detect SCAN. Thus, the BRS analysis considering delayed reaction in the dynamics of heart rate variability may contribute to an accurate screening tool to staging CAN, in addition to indicating patients with most insidious disease progress.

Cardiac ventricular sizes are reduced in patients with long-term, normoalbuminuric type 1 diabetes compared to the non-diabetic background population

AIMS

Type 1 diabetes entails increased cardiovascular morbidity and cardiac chamber sizes are associated with cardiovascular disease. The aim of this study was to compare cardiac chamber sizes in normoalbuminuric persons with type 1 diabetes to a background population without diabetes.

METHODS

In a cross-sectional study, we examined 71 normoalbuminuric persons with long-term type 1 diabetes without known cardiovascular disease using cardiac multi-detector computed tomography. Cardiac chamber sizes and left ventricular remodelling were compared to persons without diabetes from the Copenhagen General Population Study.

RESULTS

Participants were median (interquartile range) 54 (48-60) (type 1 diabetes) and 57 (50-64) (without diabetes) years old and 59% were men (both groups). Participants with type 1 diabetes had smaller left ventricular mass (-3.5 g/m², 95% confidence interval -5.8 to -1.3) and left (-4.0 mL/m², 95% confidence interval -6.9 to -1.0) and right (-11.7 mL/m², 95% confidence interval -15.4 to -7.9) ventricular volumes in multivariable analyses (adjusted for age, sex, body composition, blood pressure and antihypertensive medication), but no differences in atrial volumes.

CONCLUSION

Persons with long-term type 1 diabetes had smaller left ventricular mass and biventricular volumes, yet similar atrial sizes, compared to a background population without diabetes. These findings may reflect subclinical development of diabetic cardiomyopathy.

Predisposing factors to heart failure in diabetic nephropathy: a look at the sympathetic nervous system hyperactivity

Diabetes mellitus (DM) and heart failure (HF) are frequent comorbidities among elderly patients. HF, a leading cause of mortality and morbidity worldwide, is characterized by sympathetic nervous system hyperactivity. The prevalence of diabetes mellitus (DM) is rapidly growing and the risk of developing HF is higher among DM patients. DM is responsible for several macro- and micro-angiopathies that contribute to the development of coronary artery disease (CAD), peripheral artery disease, retinopathy, neuropathy and diabetic nephropathy (DN) as well. Independently of CAD, chronic kidney disease (CKD) and DM increase the risk of HF. Individuals with diabetic nephropathy are likely to present a distinct pathological condition, defined as diabetic cardiomyopathy, even in the absence of hypertension or CAD, whose pathogenesis is only partially known. However, several hypotheses have been proposed to explain the mechanism of diabetic cardiomyopathy: increased oxidative stress, altered substrate metabolism, mitochondrial dysfunction, activation of renin-angiotensin-aldosterone system (RAAS), insulin resistance, and autonomic dysfunction. In this review, we will focus on the involvement of sympathetic system hyperactivity in the diabetic nephropathy.

Left ventricular remodelling and cardiac chamber sizes in long-term, normoalbuminuric type 1 diabetes patients with and without cardiovascular autonomic neuropathy

AIMS

Type 1 diabetes is associated with increased cardiovascular (CV) morbidity and mortality, and cardiovascular autonomic neuropathy (CAN) is an important CV risk factor. The study aimed to explore associations between CAN and altered cardiac chamber sizes in persons with type 1 diabetes.

METHODS

This was a cross-sectional study of 71 asymptomatic, normoalbuminuric participants with long-term type 1 diabetes (39 with CAN, determined by >1 abnormal autonomic function test) examined with cardiac multi detector computed tomography scans, which allowed measurements of left ventricular mass and all four cardiac chamber volumes. Cardiac chambers were indexed according to body surface area (ml/m² or g/m²).

RESULTS

Persons with and without CAN had mean ± SD age of 57 ± 7 and 50 ± 8 years (p < 0.001) and diabetes duration of 36 ± 11 and 32 ± 9 years (p < 0.05), respectively. Increasing autonomic dysfunction, evaluated by decrease in heart rate variability during deep breathing (in beats per minute), was associated with larger right (-0.5, 95% CI -1.0 to -0.0, p < 0.05) and trend towards larger left (-0.4, 95% CI -0.8-0.0, p < 0.1) ventricular volumes in multivariable linear regression.

CONCLUSIONS

Our results suggest that impaired autonomic function may be associated with modest enlargement of ventricular volumes; this might be an early sign of progression towards heart failure.

Measuring visual cortical oxygenation in diabetes using functional near-infrared spectroscopy

AIMS

Diabetes mellitus affects about 6% of the world's population, and the chronic complications of the disease may result in macro- and micro-vascular changes. The purpose of the current study was to shed light on visual cortical oxygenation in diabetic individuals. We then aimed to compare the haemodynamic response (HDR) to visual stimulation with glycaemic control, given the likelihood of diabetic individuals suffering from such macro- and micro-vascular insult.

METHODOLOGY

Thirty participants took part in this explorative study, fifteen of whom had diabetes and fifteen of whom were non-diabetic controls. The HDR, measured as concentrations of oxyhaemoglobin [HbO] and deoxyhaemoglobin [HbR], to visual stimulation was recorded over the primary visual cortex (V1) using a dual-channel oximeter. The stimulus comprised a pattern-reversal checkerboard presented in a block design. Participants' mean glycated haemoglobin (HbA1c) level (± SD) was 7.2 ± 0.6% in the diabetic group and 5.5 ± 0.4% in the non-diabetic group. Raw haemodynamic data were normalised to baseline, and the last 15 s of data from each 'stimulus on' and 'stimulus off' condition were averaged over seven duty cycles for each participant.

RESULTS

There were statistically significant differences in ∆[HbO] and ∆[HbR] to visual stimulation between diabetic and non-diabetic groups (p < 0.05). In the diabetic group, individuals with type 1 diabetes displayed an increased [HbO] (p < 0.01) and decreased [HbR] (p < 0.05) compared to their type 2 counterparts. There was also a linear relationship between both ∆[HbO] and ∆[HbR] as a function of HbA1c level (p < 0.0005).

CONCLUSIONS

Our findings suggest that fNIRS can be used as a quantitative measure of cortical oxygenation in diabetes. Diabetic individuals have a larger HDR to visual stimulation compared to non-diabetic individuals. This increase in ∆[HbO] and decrease in ∆[HbR] appears to be correlated with HbA1c level.

Nocturnal antihypertensive treatment in patients with type 1 diabetes with autonomic neuropathy and non-dipping: a randomised, placebo-controlled, double-blind cross-over trial

OBJECTIVES

Cardiovascular autonomic neuropathy (CAN) and abnormal circadian blood pressure (BP) rhythm are independent cardiovascular risk factors in patients with diabetes and associations between CAN, non-dipping of nocturnal BP and coronary artery disease have been demonstrated. We aimed to test if bedtime dosing (BD) versus morning dosing (MD) of the ACE inhibitor enalapril would affect the 24-hour BP profile in patients with type 1 diabetes (T1D), CAN and non-dipping.

SETTING

Secondary healthcare unit in Copenhagen, Denmark.

PARTICIPANTS

24 normoalbuminuric patients with T1D with CAN and non-dipping were included, consisting of mixed gender and Caucasian origin. Mean±SD age, glycosylated haemoglobin and diabetes duration were 60±7 years, 7.9±0.7% (62±7 mmol/mol) and 36±11 years.

INTERVENTIONS

In this randomised, placebo-controlled, double-blind cross-over study, the patients were treated for 12 weeks with either MD (20 mg enalapril in the morning and placebo at bedtime) or BD (placebo in the morning and 20 mg enalapril at bedtime), followed by 12 weeks of switched treatment regimen.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was altered dipping of nocturnal BP. Secondary outcomes included a measurable effect on other cardiovascular risk factors than BP, including left ventricular function (LVF).

RESULTS

Systolic BP dipping increased 2.4% (0.03-4.9%; p=0.048) with BD compared to MD of enalapril. There was no increase in mean arterial pressure dipping (2.2% (-0.1% to 4.5%; p=0.07)). No difference was found on measures of LVF (p≥0.15). No adverse events were registered during the study.

CONCLUSIONS

We demonstrated that patients with T1D with CAN and non-dipping can be treated with an ACE inhibitor at night as BD as opposed to MD increased BP dipping, thereby diminishing the abnormal BP profile. The potentially beneficial effect on long-term cardiovascular risk remains to be determined.

TRIAL REGISTRATION NUMBER

EudraCT2012-002136-90; Post-results.

Autonomic nervous system function assessed by conventional and spectral analysis might be useful in terms of predicting retinal deterioration in persons with type 1 diabetes mellitus

AIMS

To determine whether cardiac autonomic dysfunction represents a risk factor for diabetic retinopathy (DR) development and progression in persons with type 1 diabetes mellitus (T1DM).

METHODS

The study comprised 154 normoalbuminuric persons with T1DM divided into two groups according to the DR presence: with and without DR. Cardiovascular autonomic functioning was measured at baseline using conventional and spectral analysis. Participants were re-examined for the DR presence 18months after.

RESULTS

The group with DR had longer disease duration compared to the group without DR (20 vrs 11.5years, p<0.001), heart rate coefficient of variation (HRV-CV) at rest and during deep breathing were lower in participants with DR (p=0.001 and 0.004), as well did spectral indices of HRV: low frequency (LF) band, high frequency (HF) band (p=0.003 and 0.022) while LF/HF ratio indicating sympathovagal balance was higher (p=0.037). No difference in glycaemic control or blood pressure value were observed. Twenty-one (13.36%) participants developed non proliferative DR or progressed to proliferative DR. Cox proportional regression showed that the 18months risk from retinal deterioration was reduced by 33.4% by each increase in the HRV-CV of 1%, 12.7% for the same HRV-CV increase during deep breathing while LF band of 1ms(2) results in 8.6% risk reduction.

CONCLUSIONS

This study provides evidence that DR should not be considered merely a metabolic control manifestation and that HRV-CV as well as spectral indices of HRV might serve as a practical tool to identify a subgroup of T1DM patients with higher risk of retinal deterioration.

New insights in (inter)cellular mechanisms by heart failure with preserved ejection fraction

Recently, a new paradigm for the development of heart failure with preserved ejection fraction (HFpEF) has been proposed, which identifies a systemic pro-inflammatory state induced by comorbidities as the origin of microvascular endothelial cell inflammation and subsequent concentric cardiac remodeling and dysfunction. This review further discusses the pivotal role of the inflamed endothelium in the pathogenesis of HFpEF-specific cardiac remodeling. The potential importance of reciprocal interactions of the endothelium with cardiac fibroblasts and cardiomyocytes and with the cardiac neurohumoral response in this cardiac remodeling process is outlined.

Cardiac autonomic neuropathy and early progressive renal decline in patients with nonmacroalbuminuric type 1 diabetes

BACKGROUND AND OBJECTIVES

Cardiac autonomic neuropathy predicts future adverse renal outcomes in the general population. This study sought to determine its relationship with early progressive renal decline in type 1 diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A subset of participants with normoalbuminuria (n=204) or microalbuminuria (n=166) from the First Joslin Kidney Study underwent assessment for cardiac autonomic neuropathy using heart rate variability during baseline visits performed from January 1991 to April 1992. Cardiac autonomic neuropathy was defined as an R-R variation (mean circular resultant) <20. Participants also had baseline and follow-up measurement of eGFR. Early progressive renal decline was evaluated according to two definitions: early GFR loss (slope of eGFR estimated by cystatin C <-3.3%/year) and incident advanced CKD (stage ≥3, defined by eGFR [calculated by Modification of Diet in Renal Disease method] <60 ml/min per 1.73 m(2)). Association with baseline cardiac autonomic neuropathy was assessed by adjusted logistic regression and Cox proportional hazards.

RESULTS

Among the 370 participants, 47 (13%) had baseline cardiac autonomic neuropathy, 51 (14%) had early GFR loss, and 68 (18%) had incident advanced CKD over a median 14-year follow-up. Early GFR loss occurred in 15 (32%) of the 47 patients with baseline autonomic neuropathy and in 32 (10%) of the 323 without baseline autonomic neuropathy (P<0.001). Baseline autonomic neuropathy was strongly associated with odds of early GFR loss (adjusted odds ratio, 4.09; 95% confidence interval, 1.65 to 10.12; P=0.002). Incident advanced CKD was observed in 22 (47%) of those with baseline autonomic neuropathy and 46 (14%) of those without baseline autonomic neuropathy (P<0.001). Autonomic neuropathy was independently associated with incident advanced CKD (adjusted hazard ratio, 2.76; 95% confidence interval, 1.44 to 5.30; P=0.002).

CONCLUSIONS

Cardiac autonomic neuropathy was a strong independent predictor of the long-term risk of early progressive renal decline in type 1 diabetes. Future research should explore the mechanisms by which autonomic neuropathy may be associated with renal function loss.

Cardiovascular complications in patients with autonomic failure

Patients with autonomic failure are characterized by orthostatic hypotension, supine hypertension, high blood pressure variability, blunted heart rate variability, and often have a "non-dipping" or "reverse dipping" pattern on 24-h ambulatory blood pressure monitoring. These alterations may lead to cardiovascular and cerebrovascular changes, similar to the target organ damage found in hypertension. Often patients with autonomic failure are on treatment with anti-hypotensive drugs, which may worsen supine hypertension. The aim of this review is to summarize the evidence for cardiac, vascular, renal, and cerebrovascular damage in patients with autonomic failure.

Nocturnal antihypertensive treatment in patients with type 1 diabetes with autonomic neuropathy and non-dipping of blood pressure during night time: protocol for a randomised, placebo-controlled, double-blind, two-way crossover study

INTRODUCTION

Cardiac autonomic neuropathy (CAN) and elevated nocturnal blood pressure are independent risk factors for cardiovascular disease in patients with diabetes. Previously, associations between CAN, non-dipping of nocturnal blood pressure and coronary artery calcification have been demonstrated. The present protocol describes a trial to test the efficacy of bedtime dosing of the ACE inhibitor enalapril on night time blood pressure and left ventricular mass in patients with type 1 diabetes.

MATERIALS AND METHODS

In a randomised, double-blind, two-way cross-over study, 24 normoalbuminuric patients with type 1 diabetes with CAN will be treated for 12 weeks with either morning or bedtime dosing of 20 mg enalapril, followed by 12 weeks of switched treatment regimen. During each treatment period, two 24 h ambulatory blood pressure measurements will be performed and after each treatment period left ventricular mass will be determined by multisliced CT. Primary end points will be reduction in blood pressure and reduction in left ventricular mass.

ETHICS AND DISSEMINATION

The study has been approved by the Danish Medicines Agency, the Scientific-Ethical Committee of the Capital Region of Denmark and the Danish Data Protection Agency. An external monitoring committee (the Good Clinical Practice Unit at Copenhagen University Hospital) will oversee the study. The results of the study will be presented at national and international scientific meetings and publications will be submitted to peer-reviewed journals.

TRIAL REGISTRATION NUMBER

EudraCT (2012- 002136-90).

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.

Exogenous nerve growth factor promotes the repair of cardiac sympathetic heterogeneity and electrophysiological instability in diabetic rats

OBJECTIVES

Diabetic cardiac autonomic neuropathy can lead to an increased incidence of ventricular arrhythmias (VAs). However, few data are available regarding the pathogenesis and therapy of the VAs accompanying diabetic cardiac autonomic neuropathy. We aimed to explore whether or not exogenous nerve growth factor (NGF) can reduce the sympathetic heterogeneity and the incidence of VAs in diabetes mellitus (DM).

METHODS

Male Wistar rats were randomly divided into 3 groups: controls, rats with DM with saline infused into the left stellate ganglion (LSG), i.e. the DS group and rats with DM with NGF infused into the LSG, i.e. the DN group. After 28 weeks, all rats were subjected to electrophysiological experiments. Sympathetic innervations and NGF were studied by immunostaining, RT-PCR or Western blot analysis.

RESULTS

The incidence of inducible VAs was significantly higher in the DS group than in the control group, but was markedly decreased in the DN group. In the DS group, the tyrosine hydroxylase (TH) and NGF expression were significantly lower than in the other groups, and significant proximal-distal heterogeneities existed regarding the TH and NGF expression in the left ventricle, but were markedly repaired in the DN group.

CONCLUSIONS

NGF intervention in the LSG can reduce the heterogeneity of cardiac sympathetic innervations and the incidence of VAs in diabetic rats.

Effects of triple antioxidant therapy on measures of cardiovascular autonomic neuropathy and on myocardial blood flow in type 1 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

We evaluated the effects of a combination triple antioxidant therapy on measures of cardiovascular autonomic neuropathy (CAN) and myocardial blood flow (MBF) in patients with type 1 diabetes.

METHODS

This was a randomised, parallel, placebo-controlled trial. Participants were allocated to interventions by sequentially numbered, opaque, sealed envelopes provided to the research pharmacist. All participants and examiners were masked to treatment allocation. Participants were evaluated by cardiovascular autonomic reflex testing, positron emission tomography with [(11)C]meta-hydroxyephedrine ([(11)C]HED) and [(13)N]ammonia, and adenosine stress testing. Markers of oxidative stress included 24 h urinary F2-isoprostanes. Diabetic peripheral neuropathy (DPN) was evaluated by symptoms, signs, electrophysiology and intra-epidermal nerve fibre density. Randomised participants included 44 eligible adults with type 1 diabetes and mild-to-moderate CAN, who were aged 46 ± 11 years and had HbA1c 58 ± 5 mmol/mol (7.5 ± 1.0%), with no evidence of ischaemic heart disease. Participants underwent a 24-month intervention, consisting of antioxidant treatment with allopurinol, α-lipoic acid and nicotinamide, or placebo. The main outcome was change in the global [(11)C]HED retention index (RI) at 24 months in participants on the active drug compared with those on placebo.

RESULTS

We analysed data from 44 participants (22 per group). After adjusting for age, sex and in-trial HbA1c, the antioxidant regimen was associated with a slight, but significant worsening of the global [(11)C]HED left ventricle RI (-0.010 [95% CI -0.020, -0.001] p = 0.045) compared with placebo. There were no significant differences at follow-up between antioxidant treatment and placebo in the global MBF, coronary flow reserve, or in measures of DPN and markers of oxidative stress. The majority of adverse events were of mild-to-moderate severity and did not differ between groups

CONCLUSIONS/INTERPRETATION

In this cohort of type 1 diabetes patients with mild-to-moderate CAN, a combination antioxidant treatment regimen did not prevent progression of CAN, had no beneficial effects on myocardial perfusion or DPN, and may have been detrimental. However, a larger study is necessary to assess the underlying causes of these findings.

Impaired diastolic function and elevated Nt-proBNP levels in type 1 diabetic patients without overt cardiovascular disease

Diabetic cardiomyopathy is an important complication of type 1 diabetes mellitus. Diastolic heart failure is an early manifestation of diabetic cardiac disease. Nt-proBNP is a valuable marker of ventricular dysfunction. The aim of this study was to determine Nt-proBNP concentrations in type 1 diabetic patients and determine their relationship with ventricular diastolic dysfunction (DD) and carotid artery intima media thickness (CIMT) measurements. Sixty-seven type 1 diabetic patients (30.2 ± 8.0 years; W/M: 24/43) without known cardiovascular disease and 48 healthy controls (30.5 ± 6.4 years; W/M: 19/29) were recruited. Nt-proBNP levels were measured. Conventional and tissue Doppler echocardiography were used to evaluate left ventricular diastolic function and CIMT. Nt-proBNP in diabetic patients was significantly higher than in controls (38 ± 34.8 vs. 15.1 ± 12.7 pg/ml) (P = 0.004). Ea level was higher (12.3 ± 3 vs. 10.3 ± 4 cm/s, P = 0.003) and E/Ea ratio was lower in patients (6.6 ± 2.5 vs. 9.7 ± 5.9, P = 0.001) compared with controls. Ratio of DD was higher in patients than controls (11.1 vs. 2.1%, P = 0.01). CIMT measurements in diabetic patients were higher than controls (0.54 ± 0.11 vs. 0.48 ± 0.05 mm, P = 0.02). Logistic regression revealed age and HbA1c to be independently associated with the presence of DD. Nt-proBNP levels are elevated in type 1 diabetic patients without overt cardiovascular disease and the presence of DD is increased in diabetic patients in comparison with controls. Nt-proBNP levels do not seem to be related to the presence of DD and subclinical atherosclerosis in this group of patients.

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.

What do we know and we do not know about cardiovascular autonomic neuropathy in diabetes

Cardiovascular autonomic neuropathy (CAN) in diabetes is generally overlooked in practice, although awareness of its serious consequences is emerging. Challenges in understanding the complex, dynamic changes in the modulation of the sympathetic/parasympathetic systems' tone and their interactions with physiologic mechanisms regulating the control of heart rate, blood pressure, and other cardiovascular functions in the presence of acute hyper-or-hypoglycemic stress, other stressors or medication, and challenges with sensitive evaluations have contributed to lower CAN visibility compared with other diabetes complications. Yet, CAN is a significant cause of morbidity and mortality, due to a high-risk of cardiac arrhythmias, silent myocardial ischemia and sudden death. While striving for aggressive risk factor control in diabetes practice seemed intuitive, recent reports of major clinical trials undermine established thinking concerning glycemic control and cardiovascular risk. This review covers current understanding and gaps in that understanding of the clinical implications of CAN and prevention and treatment 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.

Myocardial structure, function, and scar in patients with type 1 diabetes mellitus

BACKGROUND

We report relationships between cardiovascular disease risk factors and myocardial structure, function, and scar in patients with type 1 diabetes mellitus in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study.

METHODS AND RESULTS

Cardiac magnetic resonance was obtained in 1017 patients with type 1 diabetes mellitus. Gadolinium cardiac magnetic resonance was also obtained in 741 patients. The mean age was 49±7 years; 52% were men; and mean duration of diabetes mellitus was 28±5 years. Associations of cardiovascular disease risk factors with cardiac magnetic resonance parameters were examined with linear and logistic regression models. History of macroalbuminuria was positively associated with left ventricular mass (by 14.8 g), leading to a significantly higher ratio of left ventricular mass to end-diastolic volume (by 8%). Mean hemoglobin A(1c) levels over the preceding 22 years were inversely associated with end-diastolic volume (-3.0 mL per unit mean hemoglobin A(1c) percent) and stroke volume (-2.3 mL per unit mean hemoglobin A(1c) percent) and positively related to the ratio of elevated left ventricular mass to end-diastolic volume (0.02 g/mL per unit). The overall prevalence of myocardial scar was 4.3% by cardiac magnetic resonance and 1.4% by clinical adjudication of myocardial infarction. Both mean hemoglobin A(1c) (odds ratio, 1.5 [95% confidence interval, 1.0-2.2] per unit) and macroalbuminuria (odds ratio, 3.5 [95% confidence interval, 1.2-9.9]) were significantly associated with myocardial scar and traditional cardiovascular disease risk factors.

CONCLUSIONS

In addition to traditional cardiovascular disease risk factors, elevated mean hemoglobin A(1c) and macroalbuminuria were significantly associated with alterations in left ventricular structure and function. The prevalence of myocardial scar was 4.3% in this subcohort of DCCT/EDIC participants with relatively preserved renal function. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00360893 and NCT00360815.

Diabetic neuropathy and heart failure: role of neuropeptides

Cardiovascular autonomic neuropathy (CAN), in which patients present with damage of autonomic nerve fibres, is one of the most common complications of diabetes. CAN leads to abnormalities in heart rate and vascular dynamics, which are features of diabetic heart failure. Dysregulated neurohormonal activation, an outcome of diabetic neuropathy, has a significant pathophysiological role in diabetes-associated cardiovascular disease. Key players in neurohormonal activation include cardioprotective neuropeptides and their receptors, such as substance P (SP), neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP). These neuropeptides are released from the peripheral or autonomic nervous system and have vasoactive properties. They are further implicated in cardiomyocyte hypertrophy, calcium homeostasis, ischaemia-induced angiogenesis, protein kinase C signalling and the renin-angiotensin-aldosterone system. Therefore, dysregulation of the expression of neuropeptides or activation of the neuropeptide signalling pathways can negatively affect cardiac homeostasis. Targeting neuropeptides and their signalling pathways might thus serve as new therapeutic interventions in the treatment of heart failure associated with diabetes. This review discusses how neuropeptide dysregulation in diabetes might affect cardiac functions that contribute to the development of heart failure.

Association of cardiac autonomic neuropathy with subclinical myocardial dysfunction in type 2 diabetes

OBJECTIVES

The purpose of this study was to investigate the independent association between global cardiac autonomic neuropathy (CAN) and left ventricular (LV) dysfunction in addition to regional associations of LV dysinnervation and function, in patients with type 2 diabetes mellitus (T2DM).

BACKGROUND

CAN represents a potential mechanism in the etiology of nonischemic diabetic cardiomyopathy.

METHODS

Clinical measures of CAN based on total spectral power of heart rate variability and cardiac reflex testing and echocardiographic assessment of LV function were performed in 118 patients with type 2 diabetes mellitus. Systolic and diastolic function were defined at rest and peak exercise using peak systolic and peak early diastolic (Em) tissue velocities, calculated in 6 basal- and mid-segments using color tissue Doppler. Iodine 123-metaiodobenzylguanidine imaging was performed in 33 patients to directly quantify global (heart/mediastinum ratio) and regional LV sympathetic integrity.

RESULTS

Patients with CAN demonstrated higher resting heart rate, systolic and mean blood pressures, aortic stiffness, hemoglobin A(1c), and urine albumin/creatinine ratio, in addition to lower peak heart rate, chronotropic index, and exercise capacity. Diastolic function (Em) was associated with CAN, evidenced by total spectral power (r = 0.42, p < 0.001) and heart/mediastinum ratio (r = 0.41, p = 0.017). Diastolic function (Em) at rest and systolic function (peak systolic tissue velocity) at rest and exercise were significantly reduced in patients with CAN. Furthermore, total spectral power was associated with Em independent of age, hypertension, metabolic factors, and other relevant contributors to LV dysfunction (β = 0.20, p = 0.035). Relative regional tracer deficits indicative of local denervation were predominant in the anterior and lateral walls (p < 0.001). Associations with regional Em, independent of global iodine 123-metaiodobenzylguanidine uptake, were identified exclusively in mid-anterior (β = 0.45, p = 0.01) and mid-lateral walls (β = 0.34, p = 0.03). However, no association was found between regional denervation and systolic or diastolic dyssynchrony.

CONCLUSIONS

The diastolic dysfunction of type 2 diabetes mellitus shows associations with both regional markers of sympathetic integrity and clinical markers of autonomic neuropathy.

Association between cardiac autonomic neuropathy and hypertension and its potential influence on diabetic complications

AIMS

To examine the association between cardiac autonomic neuropathy and hypertension and the role of this association in diabetic complications.

METHODS

We included 310 patients, 138 with Type 1 and 172 with Type 2 diabetes, 62 of them with hypertension. Cardiac autonomic neuropathy was assessed by analysing heart rate variations during three standard tests (deep breathing, lying to standing and Valsalva) and looking for postural hypotension.

RESULTS

Cardiac autonomic neuropathy was present in 123 patients and 39 also had hypertension. The prevalence of a cardiac autonomic neuropathy/hypertension association was higher in Type 2 patients (P < 0.002). The prevalence of hypertension increased with the severity of cardiac autonomic neuropathy. In multiple logistic regression analysis, cardiac autonomic neuropathy was an independent risk factor for hypertension [odds ratio 2.86 (1.54-5.32); P < 0.001]. Only confirmed or severe cardiac autonomic neuropathy (two or more abnormal function tests, respectively) were independent risk factors for hypertension (P < 0.005 and < 0.0001). Cardiac autonomic neuropathy was found in most of the patients with macrovascular complications, retinopathy or nephropathy, but a large majority of the patients with these complications exhibited the cardiac autonomic neuropathy/hypertension profile. This profile was more prevalent among the patients with coronary or peripheral artery disease or antecedent stroke than among those free of these complications (P < 0.001). In logistic regression analyses, the cardiac autonomic neuropathy/hypertension profile associated significantly with macro- and microvascular complications.

CONCLUSIONS

These data are strongly in favour of the role of cardiac autonomic neuropathy in hypertension in diabetic patients. The association of the cardiac autonomic neuropathy/hypertension profile with vascular complications is consistent with a deleterious effect on vascular hemodynamics and structure, additional to the effects of hypertension.

Cardiovascular autonomic neuropathy, HDL cholesterol, and smoking correlate with arterial stiffness markers determined 18 years later in type 1 diabetes

OBJECTIVE To examine the relationship between cardiovascular autonomic neuropathy and pulse waveform analysis (PWA) measures of arterial stiffness in a childhood-onset type 1 diabetes population. RESEARCH DESIGN AND METHODS Cardiac autonomic nerve function was measured in the baseline examination of the Pittsburgh Epidemiology of Diabetes Complications Study of childhood-onset type 1 diabetes by heart rate variability (R-R interval) during deep breathing and expressed as expiration-to-inspiration (E/I) ratio. Other cardiovascular and diabetes factors were also assessed. PWA was performed using SphgymoCor Px on 144 participants at the 18-year follow-up examination. Univariate and multivariate analyses for associations between baseline nerve function and other cardiovascular and diabetes-related factors were performed for augmentation index (AIx), augmentation pressure (AP), and subendocardial viability ratio (SEVR), a surrogate marker of myocardial perfusion. RESULTS E/I ratio correlated negatively with both AIx (r = -0.18, P = 0.03) and AP (r = -0.32, P < 0.001) and positively with SEVR (r = 0.47, P < 0.001) univariately. Lower baseline E/I ratio, HDL cholesterol, and a history of smoking were associated with higher follow-up (18 years later) AIx and AP and lower SEVR in multivariate analyses. Higher baseline HbA(1) was also associated with higher AP and lower SEVR multivariately. CONCLUSIONS Cardiovascular autonomic neuropathy is associated with increased arterial stiffness measures and decreased estimated myocardial perfusion in those with type 1 diabetes some 18 years later. This association persists after adjustment for potential confounders as well as for baseline HbA(1), HDL cholesterol, and smoking history, which were also associated with these PWA measures.

Influence of cardiovascular autonomic neuropathy on atherogenesis and heart function in patients with type 1 diabetes

AIM

Cardiovascular autonomic neuropathy (CAN) increases mortality of patients with type 1 diabetes (Type 1 DM). We set out to find out whether the presence of CAN in asymptomatic, normotensive Type 1 DM affects endothelial function (marker of atherogenesis) and left ventricle function (marker of cardiomyopathy).

METHODS

Twenty-one Type 1 DM with CAN (Group A) and 35 Type 1 DM without CAN (Group B) were enrolled in the study. None of them suffered from any cardiovascular disease nor advanced chronic complications of diabetes. Both groups were comparable in age, glycemic control, BMI, and blood pressure. Markers of endothelial dysfunction and chronic inflammation were used as indicators of incipient atherogenesis. Left ventricle function was evaluated using echocardiography.

RESULTS

Both groups did not differ in any parameter of atherogenesis. However we found a statistically significant difference in values characterizing systolic and diastolic left ventricle functions between the groups.

CONCLUSIONS

CAN is not associated with elevation of markers of endothelial dysfunction and chronic inflammation in normotensive asymptomatic Type 1 DM. However CAN is associated with the impairment of systolic and diastolic left ventricle function and can thus be regarded as one of the risk factors of diabetic cardiomyopathy.

[Cardiovascular autonomous dysfunction in diabetics: the influence of disease duration, glycoregulation degree and diabetes type]

INTRODUCTION

Cardiovascular autonomous neuropathy (CAN) in diabetes has not been still defined clinically and aetiopathogenetically.

OBJECTIVE

The aim of this study was to determine the influence of disease duration, glycoregulation degree and diabetes type on damage of the cardiovascular part of the autonomous nervous system in our group of patients.

METHOD

This study included diabetics, (100 patients) the same number of patients with diabetes type I and II as well as 20 healthy individuals in the control group. Classic Ewing's cardiovascular tests were used for CAN diagnosis: (1) the cardiovascular response to Valsalva manoeuvre, (2) the cardiovascular response to deep breathing (the so-called E/I ratio), (3) the cardiovascular response to rising (the so-called 30/15 ratio), (4) the test of orthostatic hypotension and (5) the TA response to handgrip. It has been arbitrarily taken that patients, whose score of "parasympathetic" tests (Valsalva manoeuvre, E/I ratio, 30/15) is equal or bigger than 1.5 (out of possible 3), have damage of the parasympathetic part of the autonomous nervous system while patients, whose score of "sympathetic tests" (the test of orthostatic hypotension and TA response to hand-grip is equal or bigger than 1 (out of possible 2), have damage of the sympathetic part of the autonomous nervous system. The patients whose total score is equal or bigger than 2 have cardiovascular autonomous neuropathy. The glycoregulation degree is determined by the level of HbA1c.

RESULTS

There is a statistically significant, positive correlation between the values of the parasympathetic score and disease duration as well as between the total score, that is, CAN and disease duration. The connection between the sympathetic score, that is, damage of the sympathetic part of the autonomous nervous system and disease duration has not been observed. There is a positive correlation between the values of the parasympathetic score and HbA1c. The same pattern exists regarding the ratio of damage of the sympathetic part of the autonomous nervous system and the value of HbAlc, as well as the ratio of CAN, that is, the total score and HbA1c. Almost twofold, a bigger coefficient of correlation between the sympathetic score and HbA1c in relation to the coefficient of correlation of the parasympathetic score and HbA1c, points to bigger sensitivity of the sympathetic part of the autonomous nervous system to subacute deterioration of glycoregulation. The correlation between the values of autonomous scores and diabetes type has not been noted.

CONCLUSION

Our results show that besides disease duration, the subacute deterioration of glycoregulation also leads to the appearance of cardiovascular autonomous dysfunction in diabetes. The sympathetic nervous tissue is functionally more sensitive than the parasympathetic one to metabolic disorders in diabetes. The cardiovascular autonomous dysfunction will occur independently of the type of diabetes.

Early signs of left ventricular dysfunction in adolescents with type 1 diabetes mellitus: the importance of impaired circadian modulation of blood pressure and heart rate

Diabetic cardiomyopathy is a well-defined complication of diabetes that occurs in the absence of ischemic heart disease or hypertension. Moreover impaired circadian blood pressure (BP) variation has been associated with autonomic dysfunction. The aim of our study was to evaluate diurnal BP fluctuations and autonomic function and their association with left ventricular function in adolescents with Type 1 diabetes mellitus (T1DM). In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (+/-SD) age of 17.3 (+/-4.1) yr and a mean (+/-SD) diabetes duration of 8.5 (+/-3.3) yr, 24-h ambulatory BP was recorded. Moreover 24-h heart rate (HR) monitoring was performed. Myocardial structural parameters were studied by echocardiogram. Left ventricular end-diastolic (EDDLV) and end-systolic diameters (ESDLV) were estimated and left ventricular mass index (LVMI) was calculated using the Devereux formula. The patients were divided into 2 groups according to the absence of decrease (non-dippers) or the decrease (dippers) of nocturnal diastolic BP (DBP). The non-dippers showed, in comparison with the dippers, reduced mean 24-h HR (79.6 vs 84.0 beats/min, p=0.05) and reduced mean day-time HR (81.3 vs 86.0 beats/min, p=0.05). The nondippers also presented greater ESDLV (28.7 vs 25.9 mm, p=0.001) and EDDLV (47.8 vs 45.1 mm, p=0.040), and LVMI (90.2 vs 78.3 g/m2, p=0.044), in comparison with the dippers. During stepwise multiple regression, the most important variables affecting LVMI were mean HR (day): (b=-0.40, p=0.001), high frequency domain variable of HR variability (b=0.38, p=0.016) and glycosylated hemoglobin (b=0.67, p=0.001). In conclusion, we found that a group of normotensive diabetic adolescents with impaired nocturnal BP reduction, also had autonomic dysfunction, together with impaired left ventricular function. These findings suggest that there is a close relationship between autonomic function and left ventricular remodeling in patients with T1DM, which may be attributed to altered diurnal BP profile, autonomic neuropathy and poor glycemic control.

Impact of autonomic neuropathy on left ventricular function in normotensive type 1 diabetic patients: a tissue Doppler echocardiographic study

Cardiovascular autonomic neuropathy (CAN) is one of the most serious complications of diabetes and has been weakly linked with left ventricular (LV) diastolic dysfunction. Previous studies that explored this association either suffer from inadequate definition of CAN or have mainly used conventional Doppler or nuclear techniques to investigate LV diastolic function. Tissue Doppler imaging (TDI) has evolved as a new quantitative tool for the assessment of cardiac systolic function, diastolic function, and the hemodynamics of LV filling. We sought to investigate conventional and TDI-derived indexes of LV systolic and diastolic function in type 1 diabetic patients with and without CAN and also in normal control subjects. Our findings suggest that the presence of CAN seems to have an additive effect on LV diastolic dysfunction in type 1 diabetes.

QT interval prolongation in association with impaired circadian variation of blood pressure and heart rate in adolescents with Type 1 diabetes

AIMS

The aim of our study was to assess diurnal blood pressure (BP) and heart rate variability and their possible relationship to the duration of the QT interval in adolescents with Type 1 diabetes.

METHODS

In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (+/- sd) age of 17.3 (+/- 4.1) years and a mean (+/- sd) diabetes duration of 8.5 (+/- 3.3) years, 24-h ambulatory BP was recorded. In addition, 24-h heart rate (HR) monitoring was performed and QT and corrected QT (QTc) intervals were estimated as indices of autonomic function. The patients were divided into two groups according to the absence of a decrease (non-dippers) or the presence of a decrease (dippers) in nocturnal diastolic BP (DBP).

RESULTS

In comparison with the dippers, the non-dippers showed reduced mean 24-h HR (79.6 vs. 84.0 beats/min, P = 0.05) and reduced mean daytime HR (81.3 vs. 86.0 beats/min, P = 0.05). The QT interval was prolonged in the non-dippers (366.3 vs. 347.5 ms, P = 0.015), and end systolic (28.7 vs. 25.9 mm, P = 0.004) and end diastolic left ventricular diameters (47.8 vs. 45.5 mm, P = 0.037) were greater. In stepwise multiple regression, HR variables were the most important factors affecting DBP ratio or the duration of the QT interval.

CONCLUSIONS

In conclusion, normotensive diabetic adolescents with impaired nocturnal BP reduction also have impaired autonomic function tests, in association with prolonged QT interval and increased left ventricular diameters. These findings suggest that diabetic adolescents who have the 'non-dipper' phenomenon may need close follow-up for the possible development of vascular complications, such as cardiac arrhythmias and left-ventricular hypertrophy.

Cardiovascular autonomic neuropathy: diagnosis and management

Cardiovascular autonomic neuropathy increases morbidity and mortality, and reduces quality of life and activities of daily living of the patients with diabetes. The reduced cardiovascular autonomic function as measured by heart rate variability is strongly associated with an increased risk of silent myocardial ischemia and mortality. Currently, no specific therapeutic strategies can be recommended for cardiac autonomic neuropathy, but management of hyperglycemia and the use of angiotensin-converting enzyme inhibitors and beta blockers should be instituted.

Regression of Left Ventricular Hypertrophy in Diabetic Nephropathy: Loss of Parasympathetic Function Predicts Response to Treatment

Both left ventricular (LV) hypertrophy and decreased autonomic function are predictors of adverse cardiac events. Patients with diabetic nephropathy have an excess cardiovascular risk. The authors determined heart rate variability from 24-hour ambulatory electrocardiographic recordings and measures of LV mass with systolic and diastolic function from echocardiograms. Patients with diabetic nephropathy (n=16) were seen weekly for insulin and hypertension management. Glycohemoglobin decreased from 9.5+/-0.4% to 8.3+/-0.4% (p=0.01), and advanced glycated end products decreased from 12.1+/-2.2 to 7.4+/-1.2 units (p=0.03). Mean arterial pressure and body weight did not change. Serum creatinine increased (1.8+/-0.1 mg/dL to 2.0+/-0.2 mg/dL; p=0.03). The authors used a panel of markers of baseline heart rate variation to assess autonomic function. When covariance of the heart rate interval results were evaluated, the group below the median was found to have a significant decrease in LV mass, from 230 g to 184 g (p=0.013); the group above the median had an increase (182 g to 193 g; p=0.5329). Baseline covariance of the heart rate interval predicted 12-month changes in LV mass in 13 of 16 patients (predictive accuracy, 81%). Improvement in measures of heart rate variation correlated with a decrease in LV mass. Parallel improvement of LV mass and autonomic function suggests a common mechanism, allowing for prediction of LV mass improvement through analysis of baseline heart rate variation.