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

Cardiovascular autonomic neuropathy and the risk of diabetic kidney disease

Background

Cardiovascular autonomic neuropathy (CAN) is known to affect patients with diabetes mellitus (DM) and cause adverse renal outcomes. We aimed to analyze the association between CAN and diabetic kidney disease (DKD).

Method

We enrolled 254 DM patients (mean age, 56.7 ± 15.2 years; male: female ratio, 1.17:1) with 19 (7.5%) type 1 DM patients and 235 (92.5%) type 2 DM patients. All patients had undergone cardiovascular autonomic function tests between January 2019 and December 2021 in a tertiary hospital in Korea. Cardiovascular autonomic neuropathy was categorized as normal, early, or definite after measuring three heart rate variability parameters. Diabetic kidney disease refers to a persistently elevated urinary albumin-creatinine ratio (uACR ≥30 mg/g) or reduced estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m2). Logistic and Cox regression analyses were performed.

Results

Patients with elevated uACR (n=107) and reduced eGFR (n=32) had a higher rate of definite CAN. After adjusting for covariates, definite CAN was associated with elevated uACR (OR=2.4, 95% CI 1.07-5.36) but not with reduced eGFR (OR=3.43, 95% CI 0.62-18.90). A total of 94 patients repeated uACR measurements within 2 years (mean follow-up, 586.3 ± 116.8 days). Both definite and early CAN were independent risk factors for elevated uACR (HR=8.61 and 8.35, respectively; both p<0.05). In addition, high-density lipoprotein cholesterol, ACE inhibitors/angiotensin receptor blockers and glucagon-like peptide-1 receptor agonists were independent protective factors for elevated uACR (HR=0.96, 0.25, and 0.07, respectively; all p<0.05).

Conclusion

Cardiovascular autonomic neuropathy is a potential indicator of DKD. Comprehensive management of DKD in the early stages of CAN may prevent microalbuminuria.

Features characterising cardiac autonomic neuropathy in diabetes using ensembled classification

OBJECTIVE

Using supervised machine learning to classify the severity of cardiovascular autonomic neuropathy (CAN). The aims were 1) to investigate which features contribute to characterising CAN 2) to generate an ensembled set of features that best describes the variation in CAN classification.

METHODS

Eighty-two features from demographic, beat-to-beat, biochemical, and inflammation were obtained from 204 people with diabetes and used in three machine-learning-classifiers, these are: support vector machine, decision tree, and random forest. All data were ensembled using a weighted mean of the features from each classifier.

RESULTS

The 10 most important features derived from the domains: Beat-to-beat, inflammation markers, disease-duration, and age.

CONCLUSIONS

Beat-to-beat measures associate with CAN as diagnosis is mainly based on cardiac reflex responses, disease-duration and age are also related to CAN development throughout disease progression. The inflammation markers may reflect the underlying disease process, and therefore, new treatment modalities targeting systemic low-grade inflammation should potentially be tested to prevent the development of CAN.

SIGNIFICANCE

Cardiac reflex responses should be monitored closely to diagnose and classify severity levels of CAN accurately. Standard clinical biochemical analytes, such as glycaemic level, lipidic level, or kidney function were not included in the ten most important features. Beat-to-beat measures accounted for approximately 60% of the features in the ensembled data.

The Retinal Nerve Fiber Layer Thickness Is Associated with Systemic Neurodegeneration in Long-Term Type 1 Diabetes

Purpose

To determine whether the retinal nerve fiber layer thickness can be used as an indicator for systemic neurodegeneration in diabetes.

Methods

We used existing data from 38 adults with type 1 diabetes and established polyneuropathy. Retinal nerve fiber layer thickness values of four scanned quadrants (superior, inferior, temporal, and nasal) and the central foveal thickness were extracted directly from optical coherence tomography. Nerve conduction velocities were recorded using standardized neurophysiologic testing of the tibial and peroneal motor nerves and the radial and median sensory nerves, 24-hour electrocardiographic recordings were used to retrieve time- and frequency-derived measures of heart rate variability, and a pain catastrophizing scale was used to assess cognitive distortion.

Results

When adjusted for hemoglobin A1c, the regional thickness of the retinal nerve fiber layers was (1) positively associated with peripheral nerve conduction velocities of the sensory and motor nerves (all P < 0.036), (2) negatively associated with time and frequency domains of heart rate variability (all P < 0.033), and (3) negatively associated to catastrophic thinking (all P < 0.038).

Conclusions

Thickness of the retinal nerve fiber layer was a robust indicator for clinically meaningful measures of peripheral and autonomic neuropathy and even for cognitive comorbidity.

Translational Relevance

The findings indicate that the thickness of the retinal nerve fiber layer should be studied in adolescents and people with prediabetes to determine whether it is useful to predict the presence and severity of systemic neurodegeneration.

Reactive Hyperemia and Cardiovascular Autonomic Neuropathy in Type 2 Diabetic Patients: A Systematic Review of Randomized and Nonrandomized Clinical Trials

Objective: This work aimed to determine the relationship between the autonomic nervous system and reactive hyperemia (RH) in type 2 diabetes patients with and without cardiovascular autonomic neuropathy (CAN). Methodology: A systematic review of randomized and nonrandomized clinical studies characterizing reactive hyperemia and autonomic activity in type 2 diabetes patients with and without CAN was performed. Results: Five articles showed differences in RH between healthy subjects and diabetic patients with and/or without neuropathy, while one study did not show such differences between healthy subjects and diabetic patients, but patients with diabetic ulcers had lower RH index values compared to healthy controls. Another study found no significant difference in blood flow after a muscle strain that induced reactive hyperemia between normal subjects and non-smoking diabetic patients. Four studies measured reactive hyperemia using peripheral arterial tonometry (PAT); only two found a significantly lower endothelial-function-derived measure of PAT in diabetic patients than in those without CAN. Four studies measured reactive hyperemia using flow-mediated dilation (FMD), but no significant differences were reported between diabetic patients with and without CAN. Two studies measured RH using laser Doppler techniques; one of them found significant differences in the blood flow of calf skin after stretching between diabetic non-smokers and smokers. The diabetic smokers had neurogenic activity at baseline that was significantly lower than that of the normal subjects. The greatest evidence revealed that the differences in RH between diabetic patients with and without CAN may depend on both the method used to measure hyperemia and that applied for the ANS examination as well as the type of autonomic deficit present in the patients. Conclusions: In diabetic patients, there is a deterioration in the vasodilator response to the reactive hyperemia maneuver compared to healthy subjects, which depends in part on endothelial and autonomic dysfunction. Blood flow alterations in diabetic patients during RH are mainly mediated by sympathetic dysfunction. The greatest evidence suggests a relationship between ANS and RH; however, there are no significant differences in RH between diabetic patients with and without CAN, as measured using FMD. When the flow of the microvascular territory is measured, the differences between diabetics with and without CAN become evident. Therefore, RH measured using PAT may reflect diabetic neuropathic changes with greater sensitivity compared to FMD.

Emerging Therapy for Diabetic Cardiomyopathy: From Molecular Mechanism to Clinical Practice

Diabetic cardiomyopathy is characterized by abnormal myocardial structure or performance in the absence of coronary artery disease or significant valvular heart disease in patients with diabetes mellitus. The spectrum of diabetic cardiomyopathy ranges from subtle myocardial changes to myocardial fibrosis and diastolic function and finally to symptomatic heart failure. Except for sodium–glucose transport protein 2 inhibitors and possibly bariatric and metabolic surgery, there is currently no specific treatment for this distinct disease entity in patients with diabetes. The molecular mechanism of diabetic cardiomyopathy includes impaired nutrient-sensing signaling, dysregulated autophagy, impaired mitochondrial energetics, altered fuel utilization, oxidative stress and lipid peroxidation, advanced glycation end-products, inflammation, impaired calcium homeostasis, abnormal endothelial function and nitric oxide production, aberrant epidermal growth factor receptor signaling, the activation of the renin–angiotensin–aldosterone system and sympathetic hyperactivity, and extracellular matrix accumulation and fibrosis. Here, we summarize several important emerging treatments for diabetic cardiomyopathy targeting specific molecular mechanisms, with evidence from preclinical studies and clinical trials.

The conundrum of diabetic neuropathies-Past, present, and future

Diabetic neuropathy (DN) remains arguably the most prevalent chronic complication in people with both type 1 and type 2 diabetes, including in youth, despite changes in the current standards of clinical care. Additionally, emerging evidence demonstrates that neuropathy affects a large proportion of people with undiagnosed diabetes and/or prediabetes, as well as those with obesity. Here we summarize the latest epidemiology of DN, recent findings regarding the pathophysiology of the disease, as well as current outcome measures for screening and diagnosis, in research and clinical settings. The authors discuss novel perspectives on the impact of social determinants of health in DN development and management, and the latest evidence on effective therapies, including pharmacological and nonpharmacological therapies for neuropathic pain. Throughout the publication, we identify knowledge gaps and the need for future funding to address these gaps, as well as needs to advocate for a personalized care approach to reduce the burden of DN and optimize quality of life for all affected individuals.

SUDOSCAN, an Innovative, Simple and Non-Invasive Medical Device for Assessing Sudomotor Function

Diabetic autonomic neuropathy is probably the most undiagnosed but serious complication of diabetes. The main objectives were to assess the prevalence of peripheral and autonomic neuropathy in a population of diabetic patients, analyze it in a real-life outpatient unit scenario and determine the feasibility of performing SUDOSCAN tests together with widely used tests for neuropathy. A total of 33 patients were included in the study. Different scoring systems (the Toronto Clinical Neuropathy Score-TCNS; the Neuropathy Disability Score-NDS; and the Neuropathy Symptom Score-NSS) were applied to record diabetic neuropathy (DN), while the SUDOSCAN medical device was used to assess sudomotor function, detect diabetic autonomic neuropathy and screen for cardiac autonomic neuropathy (CAN). Fifteen (45.5%) patients had sudomotor dysfunction. The SUDOSCAN CAN risk score was positively correlated with the hands' electrochemical sweat conductance (ESC), diastolic blood pressure (DBP), the level of the glycated hemoglobin, as well as with the TCNS, NDS and NSS. Performing SUDOSCAN tests together with other tests for DN proved to be a feasible approach that could be used in daily clinical practice in order to screen for DN, as well as for the early screening of CAN, before more complex and time-consuming tests.

Cardiovascular autonomic neuropathy and the impact on progression of diabetic kidney disease in type 1 diabetes

INTRODUCTION

We investigated the association between cardiovascular autonomic neuropathy (CAN) and decline in kidney function in type 1 diabetes.

RESEARCH DESIGN AND METHODS

We included 329 persons with type 1 diabetes. CAN was assessed by cardiovascular reflex tests (CARTs): heart rate response to deep breathing (E/I ratio), to standing (30/15 ratio) and to the Valsalva maneuvre. Two or more pathological CARTs defined CAN diagnosis. Outcomes were yearly change in albuminuria or yearly change in estimated glomerular filtration rate (eGFR). An endpoint of eGFR decline >30%, development of end-stage kidney disease (ESKD) or death was examined.Associations were assessed by linear and Cox regression.

RESULTS

Participants were aged 55.2 (9.4) years, 52% were male, with a diabetes duration of 40.1 (8.9) years, HbA_1c of 7.9% (62.5 mmol/mol), eGFR 77.9 (27.7) mL/min/1.73 m², urinary albumin excretion rate of 14.5 (7-58) mg/24 hours, and 31% were diagnosed with CAN.CAN was associated with a 7.8% higher albuminuria increase per year (95% CI: 0.50% to 15.63%, p=0.036) versus no CAN. The endpoint of ESKD, all-cause mortality and ≥30% decline in eGFR was associated with CAN (HR=2.497, p=0.0254).

CONCLUSION

CAN and sympathetic dysfunction were associated with increase in albuminuria in individuals with type 1 diabetes suggesting its role as a potential marker of diabetic kidney disease progression.

Cardiovascular autonomic neuropathy in patients with schizophrenia

BACKGROUND

Cardiovascular autonomic neuropathy (CAN) is an independent predictor of cardiovascular disease (CVD) in patients with diabetes as well as in patients with pre-diabetes and metabolic syndrome. Patients with schizophrenia have an increased rate of metabolic syndrome, pre-diabetes and diabetes as compared to the general population. Despite of this, occurrence CAN has not been investigated in patient with schizophrenia. Therefore, the aims of this study were (1) to evaluate the feasibility testing for CAN with a new clinical tool and (2) report the prevalence of early and manifest CAN in patients with schizophrenia.

METHODS AND RESULTS

Patients with diagnosed schizophrenia and with a disease duration ≥10 years were matched 1:1 on age and gender at screening with psychiatric healthy controls. CAN was defined as ≥ two abnormal standard cardiovascular autonomic reflex tests (lying-to-standing, deep breathing, and Valsalva maneuver) using the Vagus^TM device. A total of 46 patients with schizophrenia were included and matched to psychiatric healthy controls. Manifest CAN were more frequently presented in patients with schizophrenia (39% vs. 6% for controls, p<.0001). Sensitivity analysis of 41 subjects with schizophrenia without diabetes matched to 41 psychiatric healthy controls, showed similar results (37% vs. 5% for controls, p<.0001).

CONCLUSION

CAN is highly prevalent in patients with schizophrenia. Testing for CAN is feasible and might be a new clinically tool for detecting early stages of CVD in patients with schizophrenia.

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

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

Risk Factors for Longitudinal Resting Heart Rate and Its Associations With Cardiovascular Outcomes in the DCCT/EDIC Study

OBJECTIVE

Individuals with diabetes have higher resting heart rate compared with those without, which may be predictive of long-term cardiovascular disease (CVD) risk. Using data from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study, we evaluated whether the beneficial effect of intensive versus conventional diabetes therapy on heart rate persisted, the factors mediating the differences in heart rate between treatment groups, and the effects of heart rate on future CVD risk.

RESEARCH DESIGN AND METHODS

Longitudinal changes in heart rate, from annual electrocardiograms over 22 years of EDIC follow-up, were evaluated in 1,402 participants with type 1 diabetes. Linear mixed models were used to assess the effect of DCCT treatment group on mean heart rate over time, and Cox proportional hazards models were used to estimate the effect of heart rate on CVD risk during DCCT/EDIC.

RESULTS

At DCCT closeout, 52% of participants were male and mean ± SD age was 33 ± 7 years, diabetes duration 12 ± 5 years, and HbA_1c 7.4 ± 1.2% (intensive) and 9.1 ± 1.6% (conventional). Through EDIC, participants in the intensive group had significantly lower heart rate in comparison with the conventional group. While significant group differences in heart rate were fully attenuated by DCCT/EDIC mean HbA_1c, higher heart rate predicted CVD and major adverse cardiovascular events independent of other risk factors.

CONCLUSIONS

After 22 years of follow-up, former intensive versus conventional therapy remained significantly associated with lower heart rate, consistent with the long-term beneficial effects of intensive therapy on CVD. DCCT treatment group effects on heart rate were explained by differences in DCCT/EDIC mean HbA_1c.

Relationship between cardiac autonomic neuropathy and cardio-metabolic risk profile in adults with type 1 diabetes

AIM

The present study aims to determine the prevalence and association of cardiac autonomic neuropathy (CAN) with some traditional cardio-metabolic risk factors in adults with type 1 diabetes (T1D).

MATERIAL AND METHODS

235 adults with T1D, divided into three groups according to diabetes duration, were recruited in this cross-sectional study from May 2017 till December 2018. Anthropometric parameters and blood pressure were measured. Lipids, liver enzymes, uric acid, creatinine, HbA1c and high sensitive C-reactive protein (hsCRP) were measured at fasting. Albumin/creatinine ratio (ACR) was measured in a first spot urine sample. Body composition was evaluated using bio-impedance analysis, Inbody720 (Biospace, USA). Advanced glycation end products (AGEs) were assessed by autofluorescence method, AGE Reader (Diagnoptics, The Netherlands). CAN was assessed by ANX-3.0 monitoring technology (ANSAR Medical Technologies, Inc., Philadelphia, PA), applying standard clinical tests. 2005 IDF and 2009 JIS definitions were used to define Metabolic Syndrome (MetS).

RESULTS

The prevalence of CAN was 23% and increased with diabetes duration. Sympathetic activity was independently related to age, albumin/creatinine ratio (ACR) and total body fat mass, and parasympathetic activity - to age and ACR. Elevated hsCRP, AGEs and body fat, diabetic retinopathy and nephropathy, as well as hypertension, dyslipidemia and metabolic syndrome were found to increase the risk of CAN in T1D.

CONCLUSION

CAN appears to be a common complication of T1D, especially with longer duration, and is found to be related to diabetic microvascular disease and metabolic syndrome components.

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

Association of Cardiovascular Autonomic Neuropathy and Distal Symmetric Polyneuropathy with All-Cause Mortality: A Retrospective Cohort Study

BACKGROUND

People with diabetic cardiovascular autonomic neuropathy (CAN) have increased cardiovascular mortality. However, the association between distal symmetric polyneuropathy (DSPN) or CAN with all-cause mortality is much less investigated. Thus, we set out to examine the effect of CAN and DSPN on all-cause mortality in a well-phenotyped cohort.

METHODS

All diabetes cases (n = 1,347) from the catchment area of a secondary diabetes care centre who had medical examination including neuropathy assessment between 1997 and 2016 were followed up for all-cause mortality in the NHS Hungary reimbursement database until 2018. We investigated the association of CAN (Ewing tests) and DSPN (Neurometer) with all-cause mortality using Cox models stratified by diabetes type.

RESULTS

Altogether, n = 131/1,011 persons with type 1/type 2 diabetes were included. Of the participants, 53%/43% were male, mean age was 46 ± 12/64 ± 10 years, diabetes duration was 13 ± 10/7 ± 8 years, 42%/29% had CAN, and 39%/37% had DSPN. During the 9 ± 5/8 ± 5-year follow-up, n = 28/494 participants died. In fully adjusted models, participants with type 1 diabetes patients with versus without DSPN had an increased mortality (HR 2.99, 95% CI 1.4-8.63), while no association with CAN was observed. In type 2 diabetes, both DSPN and CAN independently increased mortality (HR 1.32, 95% CI: 1.07-1.64, and HR 1.44, 95% CI: 1.17-1.76).

CONCLUSIONS

Our results are compatible with an increased risk of mortality in people with type 1 diabetes and DSPN. Furthermore, we report a similarly strong association between DSPN and CAN and all-cause mortality in type 2 diabetes mellitus.

Decreased glomerular filtration rate and increased albuminuria for identification of cardiovascular autonomic neuropathy in subjects with and without diabetes

OBJECTIVE

The purpose of this study was to determine the relationship between chronic kidney disease (CKD) and cardiovascular autonomic neuropathy (CAN).

RESEARCH DESIGN AND METHODS

From October 2008 to May 2011, we enrolled 218 patients with diabetes and 62 nondiabetic subjects. Heart rate variability was represented as the maximal heart rate minus the minimal heart rate (HR_max-min) during a one-minute deep breathing test. Normal, impaired cardiovascular autonomic function and CAN were defined as s HR_max-min > 15 beats/min, HR_max-min of 10-15 beats/min and HR_max-min < 10 beats/min, respectively. CKD was diagnosed if the estimated glomerular filtration rate (eGFR) was <60/min/1.73 m² or albuminuria.

RESULTS

In our sample, 19.4% of nondiabetic subjects and 49.5% of diabetic subjects had CKD. The prevalence of CAN was higher among patients with diabetes than among nondiabetic subjects (26.4 vs. 4.9%). A significant association was observed between eGFR and HR_max-min. CAN was independently associated with CKD with an adjusted odds ratio of 2.77 (95% CI, 1.15-6.68) in diabetic patients. A positive linear trend was observed for the odds of CAN with increasing CKD severity in diabetes. The areas under the curve (AUCs) for the predictive ability of eGFR for the risk of impaired cardiovascular autonomic function for nondiabetic group and CAN for the diabetic group were 0.734 and 0.703, respectively. Adding age, sex, body mass index, and albuminuria to the prediction model increased the AUCs to 0.852 and 0.791, respectively.

CONCLUSION

CKD is associated with the risk of CAN in both nondiabetic and diabetic subjects. eGFR and albuminuria improve the prediction of CAN.

Hypoglycemia unawareness and autonomic dysfunction in diabetes: Lessons learned and roles of diabetes technologies

Impaired awareness of hypoglycemia (IAH) is a reduction in the ability to recognize low blood glucose levels that would otherwise prompt an appropriate corrective therapy. Identified in approximately 25% of patients with type 1 diabetes, IAH has complex pathophysiology, and might lead to serious and potentially lethal consequences in patients with diabetes, particularly in those with more advanced disease and comorbidities. Continuous glucose monitoring systems can provide real-time glucose information and generate timely alerts on rapidly falling or low blood glucose levels. Given their improvements in accuracy, affordability and integration with insulin pump technology, continuous glucose monitoring systems are emerging as critical tools to help prevent serious hypoglycemia and mitigate its consequences in patients with diabetes. This review discusses the current knowledge on IAH and effective diagnostic methods, the relationship between hypoglycemia and cardiovascular autonomic neuropathy, a practical approach to evaluating cardiovascular autonomic neuropathy for clinicians, and recent evidence from clinical trials assessing the effects of the use of CGM technologies in patients with type 1 diabetes with IAH.

Cardiovascular autonomic neuropathy: A silent killer with long reach

Cardiovascular autonomic neuropathy (CAN) is a common and deadly complication of diabetes mellitus, which is frequently overlooked in clinical practice due to its characteristic subtle presentation earlier in disease. Yet, timely detection of CAN may help implementation of tailored interventions to prevent its progression and mitigate the risk of associated complications, including cardiovascular disease (CVD), cardiac arrhythmias, myocardial dysfunction leading to congestive heart failure and all-cause mortality. This review highlights current CAN epidemiology trends, novel mechanisms linking CAN with other diabetes complications and current recommendations for diagnosis and management of the disease in the clinical setting.

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.

The Association Between Heart Rate and Glycemic Status in the National Health and Nutrition Examination Surveys

CONTEXT

Evidence suggests that heart rate (HR) is a prognostic factor for cardiovascular disease (CVD), for which persons with diabetes are at increased risk.

OBJECTIVE

The objective of this article is to determine the association between HR and glycemic status in a nationally representative sample of US adults, and, among adults with diagnosed diabetes, the association between HR and hemoglobin A1c (HbA1c) level.

DESIGN

A cross-sectional study was conducted.

SETTING

The setting of this study is the National Health and Nutrition Examination Surveys, 2011 to 2016.

PARTICIPANTS

US general adult (age ≥ 20 years) population who had information on glycemic status based on self-report, HbA1c, and fasting plasma glucose (N = 8562).

INTERVENTION

There was no intervention.

MAIN OUTCOME MEASURE

The main outcome measure of this study was mean HR (beats per minute).

RESULTS

After adjustment for examination time, age, other demographic characteristics, health insurance, health behaviors, body mass index, CVD and kidney disease, and taking antihypertensive medications, mean HR was significantly higher for those with diagnosed (75 bpm), undiagnosed diabetes (75 bpm), and prediabetes (73 bpm) compared to those with normoglycemia (71 bpm, P < .05 for all); this association was robust both for men and women. Mean HR increased with increasing HbA1c level among individuals with diagnosed diabetes independent of other risk factors (HbA1c < 7.0% [< 53 mmol/mol], 73 bpm vs A1c ≥ 11.0% [≥ 97mmol/mol], 79 bpm, P < .001); this association was most pronounced for women.

CONCLUSIONS

Adjusted mean HR was higher among individuals with diabetes and increased glycemia, which may reflect underlying autonomic and/or myocardial dysfunction among those with diabetes.

Lumos for the long trail: Strategies for clinical diagnosis and severity staging for diabetic polyneuropathy and future directions

Diabetic polyneuropathy, which is a chronic symmetrical length-dependent sensorimotor polyneuropathy, is the most common form of diabetic neuropathy. Although diabetic polyneuropathy is the most important risk factor in cases of diabetic foot, given its poor prognosis, the criteria for diagnosis and staging of diabetic polyneuropathy has not been established; consequently, no disease-modifying treatment is available. Most criteria and scoring systems that were previously proposed consist of clinical signs, symptoms and quantitative examinations, including sensory function tests and nerve conduction study. However, in diabetic polyneuropathy, clinical symptoms, including numbness, pain and allodynia, show no significant correlation with the development of pathophysiological changes in the peripheral nervous system. Therefore, these proposed criteria and scoring systems have failed to become a universal clinical end-point for large-scale clinical trials evaluating the prognosis in diabetes patients. We should use quantitative examinations of which validity has been proven. Nerve conduction study, for example, has been proven effective to evaluate dysfunctions of large nerve fibers. Baba's classification, which uses a nerve conduction study, is one of the most promising diagnostic methods. Loss of small nerve fibers can be determined using corneal confocal microscopy and intra-epidermal nerve fiber density. However, no staging criteria have been proposed using these quantitative evaluations for small fiber neuropathy. To establish a novel diagnostic and staging criteria of diabetic polyneuropathy, we propose three principles to be considered: (i) include only generalizable objective quantitative tests; (ii) exclude clinical symptoms and signs; and (iii) do not restrictively exclude other causes of polyneuropathy.

Cardiovascular autonomic neuropathy as a cause of fatigue in chronic hypoparathyroidism

PURPOSE

Hypoparathyroidism (hypoPT) results in an impairment of quality of life (QoL), an increase in fatigue and a higher risk of mortality. Cardiovascular autonomic neuropathy (CAN) is an impairment of the cardiovascular autonomic system and is associated with increased mortality and fatigability. Patients with hypoPT show an increased risk of CAN. However, no previous studies have investigated the association between CAN and QoL in hypoPT. To test whether CAN is associated with fatigue and impaired QOL in hypoPT patients.

METHODS

We enrolled 48 subjects with postsurgical hypoPT treated with calcium and calcitriol and 38 healthy subjects who underwent thyroidectomy. Subjects completed the RAND 36-Item Short Form (SF-36) Health Survey, evaluating physical (PCS) and mental (MCS) health, and fatigue score. CAN was assessed using cardiovascular autonomic reflex tests (CARTs). Participants were considered to have "early CAN" (EC) if they had one abnormal CART and "definite CAN" (DC) with two or more abnormal CARTs.

RESULTS

Compared with controls, hypoPT population had lower fatigue scores (44.5 IQRː9 vs 38.5 IQRː12.3, P = 0.031). In the hypoPT group, only participants with DC had a lower fatigue score than subjects without CAN (DC: β: -9.55, P = 0.005) after adjusting for age, duration of disease, calcium concentration, TSH, calcitriol and calcium supplementation. No differences were found in the PCS and MCS scores in the hypoPT group.

CONCLUSIONS

CAN may explain fatigue, a common complaint of postsurgical hypoPT patients. Further larger and prospective investigations are needed to confirm our findings.

Cardiac Autonomic Neuropathy in Obesity, the Metabolic Syndrome and Prediabetes: A Narrative Review

Cardiac autonomic neuropathy (CAN) is a major complication of type 1 and type 2 diabetes mellitus (T1DM and T2DM). The increased morbidity, cardiovascular and all-cause mortality associated with CAN is established from numerous epidemiological studies. However, CAN is increasingly recognised in people with prediabetes (pre-DM) and the metabolic syndrome (MetS) with a reported prevalence up to 11% and 24% respectively. CAN is associated with components of MetS including hypertension and obesity, predating hyperglycaemia. The aetiology of CAN is multifactorial and there is a reciprocal relationship with insulin resistance and MetS. Obstructive sleep apnoea (OSA) is also associated with CAN possibly through MetS and an independent mechanism. An estimated global prevalence of the impaired glucose tolerance (IGT) form of pre-DM of 587 million people by 2045 means CAN will become a major clinical problem. CAN is independently associated with silent myocardial ischaemia, major cardiovascular events, myocardial dysfunction and cardiovascular mortality. Screening for CAN in pre-DM using risk scores with analysis of heart rate variability (HRV) or Sudoscan is important to allow earlier treatment at a reversible stage. The link between obesity and CAN highlights the therapeutic potential of lifestyle interventions including diet and physical activity to reverse MetS and prevent CAN. Weight loss achieved using these dietary and exercise lifestyle interventions improves the sympathetic and parasympathetic HRV indices of cardiac autonomic function. Further research is needed to identify high-risk populations of people with pre-DM or obesity that might benefit from targeted pharmacotherapy including metformin, sodium/glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) analogues. Bariatric surgery also improves HRV through weight loss which might also prevent CAN in severe obesity. This article reviews the literature on CAN in obesity, pre-DM and MetS, to help determine a rationale for screening, early intervention treatment and formulate future research questions in this highly prevalent condition.

Prevalence and Diagnosis of Diabetic Cardiovascular Autonomic Neuropathy in Beijing, China: A Retrospective Multicenter Clinical Study

Cardiovascular autonomic neuropathy (CAN) is a debilitating condition occurring among diabetic patients especially those with long duration of disease. Whereas incidences and treatment of CAN has been well described for Western populations, fewer studies have been conducted among the Chinese. This study, therefore, aimed to assess the prevalence of CAN among sampled Chinese diabetic patients. Accordingly, 2,048 participants with a history of type 1 diabetes mellitus (T1DM, 73) and type 2 diabetes mellitus (T2DM, 1975) were randomly sampled from 13 hospitals. Patients’ biodata were recorded, and autonomic nervous system function tests performed to aid in the preliminary diagnosis of CAN. The final CAN diagnosis was based on the Ewing’s test in which heart rate variation (HRV) values were evaluated through deep-breathing (DB), lying-to-standing (LS), and Valsalva (V) tests. Systolic blood pressure (SBP) variation values were also evaluated through LS. In the T1DM group, 61.6% patients were diagnosed with CAN and no differences were observed in the baseline and clinical data between this group and those without CAN (P > 0.05). In the T2DM group, 62.6% patients were diagnosed with CAN and statistically significant differences were found between the CAN and non- CAN group with regards to age, duration of diabetes, metformin treatment, retinopathy, and hypertension history (P < 0.05). The most common manifestations of CAN included weakness (28.6%), dizziness (23.4%), frequent urination (19.6%), upper body sweating (18.3%), and nocturia (15.9%). Additionally, duration of disease and age were independent risk factors for CAN in T1DM and T2DM, respectively. On diagnosis, a combination of the V test + LS test provided the highest sensitivity of detecting CAN among T1DM group (sensitivity = 97.6%, AUC = 0.887) while for T2DM category, DB test had the highest sensitivity (83.6%), and maximal AUC (0.856) was found with V test + DB test. The overall prevalence of diabetes with CAN in the study was up to 63%.

Trauma in the Diabetic Limb

Poorly controlled diabetes with comorbid manifestations negatively affects outcomes in lower extremity trauma, increasing the risk of short-term and long-term complications. Management strategies of patients with diabetes that experience lower extremity trauma should also include perioperative management of hyperglycemia to reduce adverse and serious adverse events.

Cardiovascular Autonomic Neuropathy as a New Complication of Postsurgical Chronic Hypoparathyroidism

Postsurgical hypoparathyroidism (hypoPT) increases fatigue and seems to affect the risk of mortality. Cardiovascular autonomic neuropathy (CAN) is an impairment of the cardiovascular autonomic system, a cause of increased mortality, and associated with increased fatigability. The aim of this study is to evaluate CAN in hypoPT and its relationship with hypocalcemia, PTH levels, and hyperphosphatemia. This is a cross-sectional study comparing 51 postsurgical hypoPT patients treated with calcium and calcitriol and 43 control subjects without any PTH/calcium/phosphate disorders who underwent thyroidectomy. CAN was assessed by heart rate (HR) response to deep breathing, HR response to the lying-to-standing test, HR response to the Valsalva maneuver, and blood pressure response to standing. Participants were considered to have "early CAN" if they had one abnormal result in the HR tests and "definite CAN" with two or more abnormal results. The prevalence of CAN was 23% in the control group and 78% in the hypoPT group (OR 11.48; 95% CI, 4.48 to 32.17). Patients with hypoPT and serum calcium (sCa) ≥8.5 mg/dL had a prevalence of early CAN of 72.4% and the prevalence was 86.4% in those with sCa <8.5 mg/dL. Definite CAN was found in 2.3% of the control group, 24.1% of the hypoPT group without hypocalcemia, and 59.1% of the hypoPT group with hypocalcemia. In the hypoPT group, the OR for definite CAN in the patients with hypocalcemia compared to the patients with normocalcemia was 4.54 (95% CI, 1.36 to 15.11). The association between low sCa and definite CAN was confirmed after adjustment for confounders with OR 13.62 (95% CI, 2.12 to 149.84). No association was found between definite CAN and PTH levels or high phosphate levels. HypoPT is associated with CAN and hypocalcemia seems to affect its severity. Larger and prospective studies are needed to confirm our findings. © 2018 American Society for Bone and Mineral Research.

Association between cardiovascular autonomic neuropathy and left ventricular hypertrophy in young patients with congenital generalized lipodystrophy

BACKGROUND

Congenital generalized lipodystrophy (CGL) is a rare disorder characterized by the absence of subcutaneous adipose tissue, severe insulin resistance, diabetes mellitus, and cardiovascular complications, including cardiac autonomic neuropathy (CAN), left ventricular hypertrophy (LVH), and atherosclerosis. The present study aimed to access the association between CAN parameters and cardiovascular abnormalities in CGL patients.

METHODS

A cross-sectional study was conducted with 10 CGL patients and 20 healthy controls matched for age, sex, BMI, and pubertal stage. We evaluated clinical, laboratory, and cardiovascular parameters-left ventricular mass index (LVMI), interventricular septum thickness (IVS), systolic and diastolic function determined by two-dimensional transthoracic echocardiography; carotid intimal media thickness (cIMT); and cQT interval. Heart rate variability (HRV) was evaluated by spectral analysis components-high frequency (HF), low frequency (LF), very low frequency (VLF), LF/HF ratio, and total amplitude spectrum (TAS)-and cardiovascular reflexes tests (postural hypotension test, respiratory, orthostatic and Valsalva coefficients).

RESULTS

In CGL group, four patients (40%) had LVH and diastolic dysfunction. HF component (parasympathetic control) was lower in LVH patients. CGL patients presented higher values of cIMT and cQT interval than heathy subjects. Inverse association between LVMI and LF (p = 0.011), IVS and LF (p = 0.007), and cIMT and leptin (p < 0.001) were observed, even after adjustments by HOMA-IR, A1c, and blood pressure. In CGL group, there were associations between LMVI and HF component (IC95%: - 1.000; - 00.553), LVMI and TAS (IC95%: - 1.000; - 0.012), and IVS and HF component (IC95%: - 1.000; - 0.371).

CONCLUSION

The association between increased LV mass and parameters of HRV provides possible speculations about the involvement of CAN in the pathophysiology of the cardiac complications, including LVH, in patients with CGL.

Prevalence of cardiovascular autonomic neuropathy and gastroparesis symptoms among patients with type 2 diabetes who attend a primary health care center

Introduction

Cardiovascular autonomic neuropathy (CAN) and gastroparesis are two types of diabetic autonomic neuropathy which could affect patients' quality of life and carry significant morbidity and mortality outcomes. The aim of this study was to estimate the prevalence and risk factors of both CAN and gastroparesis symptoms among patients with type 2 diabetes mellitus (T2DM) at primary health care level.

Methods

A cross-sectional study was conducted among 400 adults with T2DM from April 1, 2017 to March 20, 2018. CAN was defined by the presence of any of the followings: resting tachycardia, orthostatic hypotension or prolonged corrected QT interval in the electrocardiogram. Gastroparesis symptoms were assessed using a validated questionnaire: the Gastroparesis Cardinal Symptom Index.

Results

The mean age of study participants and disease duration were 55.26 ± 10.65 years and 10.77 ± 6.89 years, respectively. CAN was present in 15.3% of the participants. Hypertension, smoking, antihypertensive use, body mass index, dyslipidemia and albuminuria were significantly higher in participants with CAN than those without CAN (p<0.05). Prolonged disease duration (p = 0.007) and hypertension (p = 0.004) were independently associated with CAN. Gastroparesis symptoms were present in 6.3% of study participants and were significantly associated with those of female gender (P<0.05). Metformin use emerged as an independent predictor of the presence of at least one symptom (p = 0.001).

Conclusion

Among Saudi adults with T2DM at primary care level, the prevalence of CAN is significant and is independently related to disease duration and hypertension, indicating the importance of CAN screening, especially for those with prolonged disease duration, and the importance of controlling blood pressure in order to prevent CAN or its consequences. The prevalence of gastroparesis symptoms is 6% and is independently related to metformin use, and therefore, symptomatic screening is required to decide which patients need further evaluation.

Risk Factors for the Presence and Progression of Cardiovascular Autonomic Neuropathy in Type 2 Diabetes: ADDITION-Denmark

OBJECTIVE

To examine the course of cardiovascular autonomic neuropathy (CAN) and related cardiometabolic risk factors in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

CAN and cardiometabolic risk factors were assessed in the Danish arm of the Anglo-Danish-Dutch Study of Intensive Treatment in People With Screen-Detected Diabetes in Primary Care (ADDITION-Denmark) at 6-year (n = 777) and 13-year (n = 443) follow-up examinations. Cardiovascular autonomic reflex tests (CARTs)-that is, lying to standing, deep breathing, and the Valsalva maneuver-and 2-min resting heart rate variability (HRV) indices were obtained as the main measures of CAN. Risk factors related to CAN status, as determined by CARTs, were studied by using multivariate logistic regressions. The effects of risk factors on continuous CARTs and HRV indices, and their changes over time, were estimated in linear mixed models.

RESULTS

A progressive yet heterogeneous course of CAN occurred between the 6- and 13-year follow-ups. Higher HbA_1c, weight, BMI, and triglycerides were associated with prevalent CAN. No significant effect of risk factors on CARTs was found when they were analyzed as continuous variables. CART indices decreased over time, and a trend of decreasing HRV indices was seen. Higher HbA_1c and BMI were associated with lower HRV index values, but these differences diminished over time.

CONCLUSIONS

These data confirm that hyperglycemia, obesity, and hypertriglyceridemia are negatively related to indices of CAN, although these effects diminish over time. The observed heterogeneous course of CAN may challenge the present clinical approach of categorically classifying CARTs to diagnose CAN and the notion of CAN being irreversible.

A cardiac risk score based on sudomotor function to evaluate cardiovascular autonomic neuropathy in asymptomatic Chinese patients with diabetes mellitus

Backgrounds

Cardiac autonomic neuropathy is a common but always overlooked. More convenient diagnostic methods are needed.

Hypothesis

Cardiac autonomic neuropathy risk score evaluated by SUDOSCAN has a fine diagnostic efficacy detecting cardiac autonomic neuropathy.

Methods

This is a cross-sectional study among patients with diabetes mellitus. Subjects undertook SUDOSCAN tests and cardiac autonomic reflex tests, including heart rate variability due to Valsalva maneuver, heart rate response due to deep breathing and heart rate response due to standing up. Presenting 2 abnormal results was defined as cardiac autonomic neuropathy.

Results

Subjects with cardiac autonomic neuropathy has significantly higher cardiac autonomic neuropathy risk score (32.88±1.60 vs 27.64±1.24,P = 0.010). Cardiac autonomic neuropathy risk score was correlated significantly with the heart rate response due to deep breathing(P = 0.004). Multiple regression analysis including significant variables showed an independent association of cardiac autonomic neuropathy risk score and heart rate response due to deep breathing (P = 0.031) and age (P = 0.000). In receiver operating characteristic curve analysis evaluating the relationship between cardiac autonomic neuropathy risk score and cardiac autonomic neuropathy, The cut-off value was 20.5, with the sensitivity of 90.48%, the specificity of 29.5%, and the positive predictive value of 46.9%. In two-step diagnostic methods, Setting 20.5 as the cut-off value of cardiac autonomic neuropathy risk score and abnormal heart rate response due to standing up as the second diagnostic step’s positive result, and setting 16.5 as the cut-off value of cardiac autonomic neuropathy risk score and abnormal heart rate response due to deep breathing as the second diagnostic step’s positive result, both achieved good diagnostic efficacy.

Conclusion

Cardiac autonomic neuropathy risk score evaluated by SUDOSCAN is a good screening test for cardiac autonomic neuropathy. The two-step diagnostic methods could be considered as surrogate diagnostic methods.

Cardiac Autonomic Neuropathy in Diabetes Mellitus

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

Cardiac autonomic neuropathy in type 1 and type 2 diabetes patients

Background

Cardiac autonomic neuropathy (CAN) in diabetes is among the strongest risk markers for future global and cardiovascular mortality. The aim of this study was to analyse CAN prevalence and to compare the associations between CAN, the glycaemic control, cardiovascular risk factors, peripheral neuropathy, retinopathy and macroangiopathy in patients with type 1 (T1DM) and type 2 diabetes mellitus (T2DM).

Methods

One hundred ninety-five diabetic patients were included in this study. All patients were evaluated for detection of CAN (with standardised cardiovascular reflex tests), diabetes-related microvascular complications (polyneuropathy, retinopathy), common carotid artery intima-media thickness (IMT) and ankle-brachial index (ABI).

Results

The prevalence of CAN was 39.1% in T2DM and 61.8% in T1DM patients. Multivariate logistic regression analysis demonstrated that in T2DM, the odds [OR (95% confidence intervals)] of CAN increased with diabetes duration [1.67(1.42–1.92)], HbA1c [1.74(1.34–2.27)], cholesterol [1.01(1.00–1.01)], triglycerides [1.01(0.99–1.00)], smoking [2.35(1.23–4.49)], systolic blood pressure [1.01(1.00–1.03)], BMI [1.16(1.08–1.24)], glomerular filtration rate [0.91(0.88–0.93)], peripheral neuropathy [25.94(11.04–44.25)], retinopathy [13.13(3.03–84.73)] and IMT [10.12 (7.21–15.32)]. In T1DM, the odds of CAN increased with diabetes duration [1.62(1.13–2.31)], HbA1c [4.49(1.27–15.9)], age of patients [1.14(1.03–1.27)], glomerular filtration rate [0.94(0.89–0.99)], peripheral neuropathy [31.6(4.5–45.8)] and IMT [5.5(2.3–8.3)].

Conclusion

This study indicated that CAN is a more frequent complication in T1DM. Apart from glycaemic control, the existence of CAN is associated with potentially modifiable cardiovascular risk only in T2DM patients. The presence of other micro- and macrovascular complications increases the probability of having CAN in both types of DM (but more pronounced in T2DM).

Cardiovascular autonomic neuropathy in adolescents and young adults with type 1 and type 2 diabetes: The SEARCH for Diabetes in Youth Cohort Study

OBJECTIVE

To estimate the prevalence of and risk factors for cardiovascular autonomic neuropathy (CAN) in adolescents and young adults with type 1 and type 2 diabetes enrolled in the SEARCH for Diabetes in Youth Study.

METHODS

The study included 1646 subjects with type 1 diabetes (age 18 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.1 ± 1.9%, 76% non-Hispanic Whites) and 252 with type 2 diabetes (age 22 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.2 ± 3.0%, 45% non-Hispanic Blacks). Cross-sectional and longitudinal risk factors were assessed at baseline and follow-up visits. Area under the curve (AUC) was used to assess the longitudinal glycemic exposure and cardiovascular risk factors. CAN was assessed by time and frequency domain indices of heart rate variability (HRV). CAN was defined as the presence of ≥3 of 5 abnormal HRV indices.

RESULTS

The prevalence of CAN was 12% in adolescents and young adults with type 1 diabetes and 17% in those with type 2 diabetes. Poor long-term glycemic control (AUC HbA1c), high blood pressure, and elevated triglyceride levels were correlates of CAN in subjects with type 1 diabetes. In those with type 2 diabetes, CAN was associated with elevated triglycerides and increased urinary albumin excretion.

CONCLUSIONS

The prevalence of CAN in this multiethnic cohort of adolescents and young adults with type 1 and type 2 diabetes are comparable to those reported in adults with diabetes. Suboptimal glycemic control and elevated triglycerides were the modifiable risk factors associated with CAN.

Pathogenesis of Cardiovascular Disease in Diabetes

The most common cause of death among adults with diabetes is cardiovascular disease (CVD). In this concise review on pathogenesis of CVD in diabetes, the 4 common conditions, atherosclerosis, microangiopathy, diabetic cardiomyopathy, and cardiac autonomic neuropathy, are explored and illustrated to be caused by interrelated pathogenetic factors. Each of these diagnoses can present alone or, commonly, along with others due to overlapping pathophysiology. Although the spectrum of physiologic abnormalities that characterize the diabetes milieu is broad and go beyond hyperglycemia, the authors highlight the most relevant evidence supporting the current knowledge of potent factors that contribute to CVD in diabetes.

Cardiac autonomic neuropathy: Risk factors, diagnosis and treatment

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

A Comparative Assessment of Cardiovascular Autonomic Reflex Testing and Cardiac 123I-Metaiodobenzylguanidine Imaging in Patients with Type 1 Diabetes Mellitus without Complications or Cardiovascular Risk Factors

AIM

To compare the cardiovascular autonomic reflex tests (CARTs) with cardiac sympathetic innervation imaging with ¹²³I-metaiodobenzylguanidine (MIBG) in patients with type 1 diabetes mellitus (T1DM).

PATIENTS AND METHODS

Forty-nine patients (29 males, mean age 36 ± 10 years, mean T1DM duration 19 ± 6 years) without cardiovascular risk factors were prospectively enrolled. Participants were evaluated for autonomic dysfunction by assessing the mean circular resultant (MCR), Valsalva maneuver (Vals), postural index (PI), and orthostatic hypotension (OH). Within one month from the performance of these tests, patients underwent cardiac MIBG imaging and the ratio of the heart to upper mediastinum count density (H/M) at 4 hours postinjection was calculated (abnormal values, H/M < 1.80).

RESULTS

Twenty-nine patients (59%) had abnormal CARTs, and 37 (76%) patients had an H/M_4 < 1.80 (p = 0.456). MCR, PI, Vals, and OH were abnormal in 29 (59%), 8 (16%), 5 (10%), and 11 (22%) patients, respectively. When using H/M_4 < 1.80 as the reference standard, a cutoff point of ≥2 abnormal CARTs had a sensitivity of 100% but a specificity of only 33% for determining CAN.

CONCLUSIONS

CARTs are not closely associated with ¹²³I-MIBG measurements, which can detect autonomic dysfunction more efficiently than the former. In comparison to semiquantitative cardiac MIBG assessment, the recommended threshold of ≥2 abnormal CARTs to define cardiovascular autonomic dysfunction is highly sensitive but of limited specificity and is independently determined by the duration of T1DM.

Sudomotor dysfunction as a measure of small fiber neuropathy in type 1 diabetes

BACKGROUND

This study evaluated whether measuring the electrochemical skin conductance (ESC), as an indirect measure of sudomotor function, may be also a reliable surrogate for early cardiovascular autonomic neuropathy (CAN).

METHODS

Longitudinal study included 37 type 1 diabetes (T1D) subjects (mean age 38±13years, duration 15±7years, HbA1c 7.9±1.1%, no known complications at baseline), and 40 age-matched healthy control (HC) subjects. Mean hands ESC (ESChands) and feet (ESCfeet) were measured with the SUDOSCAN (Impeto Medical, France). CAN was assessed with heart rate variability (HRV) studies (ANSAR Inc., PA), cardiovascular autonomic reflex tests (deep-breathing, Valsalva, postural test), and positron emission tomography with sympathetic analogue [11C]meta-hydroxyephedrine. Associations between measures of CAN and ESC were estimated using Spearman correlations. Longitudinal changes were analyzed using paired t-test.

RESULTS

At baseline, there were no differences between T1D and HC in ESChands (69±14 vs. 69±13μS; P=0.84) or ESCfeet (82±8 vs. 78±9μS; P=0.12), while some indices of HRV and Valsalva ratio were significantly lower in T1D vs. HC. T1D subjects experienced a significant decline in both ESChands and ESCfeet at 12months (mean change -7.2±11.6µS, P=0.0006; -2.8±7.3µS, P=0.023 respectively). No significant correlations were consistently found between ESC and measures of CAN at baseline or at 12months.

CONCLUSION

Comparing patients with T1D to controls, no differences in ESC were observed at baseline. The associations between ESC and established measures of CAN were inconsistent, which does not support ESC as a reliable surrogate for CAN. While both hands and feet ESC declined over time, the significance of this finding is unclear and warrants further reliability testing.

Sensory and autonomic function and structure in footpads of a diabetic mouse model

Sensory and autonomic neuropathy affects the majority of type II diabetic patients. Clinically, autonomic evaluation often focuses on sudomotor function yet this is rarely assessed in animal models. We undertook morphological and functional studies to assess large myelinated and small unmyelinated axons in the db/db type II diabetes mouse model. We observed that autonomic innervation of sweat glands in the footpads was significantly reduced in db/db mice compared to control db/+ mice and this deficit was greater compared to reductions in intraepidermal sensory innervation of adjacent epidermis. Additionally, db/db mice formed significantly fewer sweat droplets compared to controls as early as 6 weeks of age, a time when no statistical differences were observed electrophysiologically between db/db and db/+ mice studies of large myelinated sensory and motor nerves. The rate of sweat droplet formation was significantly slower and the sweat droplet size larger and more variable in db/db mice compared to controls. Whereas pilocarpine and glycopyrrolate increased and decreased sweating, respectively, in 6 month-old controls, db/db mice did not respond to pharmacologic manipulations. Our findings indicate autonomic neuropathy is an early and prominent deficit in the db/db model and have implications for the development of therapies for peripheral diabetic neuropathy.

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.

Cardiovascular Autonomic Neuropathy and Cardiovascular Outcomes in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) Study

OBJECTIVE

To examine whether cardiovascular autonomic neuropathy (CAN) is an independent risk factor of cardiovascular disease (CVD) events during DCCT/EDIC.

RESEARCH DESIGN AND METHODS

Standardized cardiovascular autonomic reflex tests (R-R response to paced breathing, Valsalva maneuver, postural changes in blood pressure) were performed at DCCT baseline, every 2 years throughout DCCT, and at two time points in EDIC. CVD events were ascertained throughout the study and adjudicated by a review committee. Cox proportional hazards models were used to estimate the effect of CAN at DCCT closeout on subsequent CVD risk.

RESULTS

There were 299 adjudicated CVD events in 165 participants following the DCCT closeout assessment: 132 of 1,262 subjects (10%) without CAN at DCCT closeout who experienced 244 CVD events versus 33 of 131 subjects (25%) with CAN at DCCT closeout who experienced 55 events (hazard ratio 2.79, 95% CI 1.91-4.09 for time to first CVD event). The cumulative incidence of the first occurrence of any CVD event during EDIC was significantly higher in participants with CAN at DCCT closeout compared with those without CAN. The association remained marginally significant after adjustment for multiple risk factors, including the EDIC updated mean HbA1c. When analyzed as a continuous variable, R-R variation was significantly lower at DCCT closeout in participants who experienced a CVD event compared with those who did not (P = 0.0012).

CONCLUSIONS

In the DCCT/EDIC cohort, individuals diagnosed with CAN at DCCT closeout experienced a higher long-term risk of CVD events during follow-up in EDIC. This association was not independent of historic glycemic exposure and its metabolic memory effect, the principal determinant of both long-term CVD risk and CAN in type 1 diabetes.

Cardiac Autonomic Neuropathy: Why Should Cardiologists Care about That?

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a frequent but underdiagnosed complication of diabetes mellitus. It has a strong influence on various cardiac disorders including myocardial ischemia and infarction, hypertension, orthostatic hypotonia, heart failure, and arrhythmias. CAN can lead to severe morbidity and mortality and increase the risk of sudden cardiac death.

METHODS

This review article summarizes the latest evidence regarding the epidemiology, pathogenesis, influence on the cardiovascular system, and diagnostic methods for CAN. The methodology of this review involved analyzing available data from recent papers relevant to the topic of diabetic autonomic neuropathy and cardiac disorders.

CONCLUSIONS

The early diagnosis of CAN can improve the prognosis and reduce adverse cardiac events. Methods based on heart rate variability enable the diagnosis of CAN even at a preclinical stage. These methods are simple and widely available for use in everyday clinical practice. According to the recently published Toronto Consensus Panel on Diabetic Neuropathy, all diabetic patients should be screened for CAN. Because diabetes mellitus often coexists with heart diseases and the most common methods used for diagnosis of CAN are based on ECG, not only diabetologists but also cardiologists should be responsible for diagnosis of CAN.

The Impact of Diabetic Neuropathy on Balance and on the Risk of Falls in Patients with Type 2 Diabetes Mellitus: A Cross-Sectional Study

INTRODUCTION

Diabetic neuropathy (DN) is a prevalent complication of Type 2 Diabetes Mellitus (T2DM) with a major impact on the health of the affected patient. We hypothesized that mediated by the dysfunctionalities associated with DN's three major components: sensitive (lack of motion associated sensory), motor (impairments in movement coordination) and autonomic (the presence of postural hypotension), the presence of DN may impair the balance in the affected patients. Our study's main aim is to evaluate the possible association between the presence and severity of DN and both the balance impairment and the risk of falls in patients with T2DM.

MATERIAL AND METHOD

In this cross-sectional study we enrolled, according to a consecutive-case population-based setting 198 patients with T2DM. The presence and severity of DN was evaluated using the Michigan Neuropathy Screening Instrument, a tool which allows both diagnosing and severity staging of DN. The balance impairment and the risk of falls were evaluated using four validated and standardized tools: Berg Balance Scale (BBS), Timed-up and Go test (TUG), Single Leg Stand test (SLS) and Fall Efficacy Scale (FES-I).

RESULTS

The presence of DN was associated with significant decreases in the BBS score (40.5 vs. 43.7 points; p<0.001) and SLS time (9.3 vs. 10.3 seconds; p = 0.003) respectively increases in TUG time (8.9 vs. 7.6 seconds; p = 0.002) and FES-I score (38 vs. 33 points; p = 0.034). The MNSI score was reverse and significantly correlated with both BBS score (Spearman's r = -0.479; p<0.001) and SLS time (Spearman's r = -0.169; p = 0.017). In the multivariate regression model, we observed that patient's age, DN severity and depression's symptoms acted as independent, significant predictors for the risk of falls in patients with T2DM.

CONCLUSIONS

The presence of DN in patients with DM is associated with impaired balance and with a consecutively increase in the risk of falls.

Pupillary Light Reflexes are Associated with Autonomic Dysfunction in Bolivian Diabetics But Not Chagas Disease Patients

Autonomic dysfunction is common in Chagas disease and diabetes. Patients with either condition complicated by cardiac autonomic dysfunction face increased mortality, but no clinical predictors of autonomic dysfunction exist. Pupillary light reflexes (PLRs) may identify such patients early, allowing for intensified treatment. To evaluate the significance of PLRs, adults were recruited from the outpatient endocrine, cardiology, and surgical clinics at a Bolivian teaching hospital. After testing for Chagas disease and diabetes, participants completed conventional autonomic testing (CAT) evaluating their cardiovascular responses to Valsalva, deep breathing, and orthostatic changes. PLRs were measured using specially designed goggles, then CAT and PLRs were compared as measures of autonomic dysfunction. This study analyzed 163 adults, including 96 with Chagas disease, 35 patients with diabetes, and 32 controls. PLRs were not significantly different between Chagas disease patients and controls. Patients with diabetes had longer latency to onset of pupil constriction, slower maximum constriction velocities, and smaller orthostatic ratios than nonpatients with diabetes. PLRs correlated poorly with CAT results. A PLR-based clinical risk score demonstrated a 2.27-fold increased likelihood of diabetes complicated by autonomic dysfunction compared with the combination of blood tests, CAT, and PLRs (sensitivity 87.9%, specificity 61.3%). PLRs represent a promising tool for evaluating subclinical neuropathy in patients with diabetes without symptomatic autonomic dysfunction. Pupillometry does not have a role in the evaluation of Chagas disease patients.

Cardiovascular autonomic neuropathy

Cardiovascular autonomic neuropathy often goes unrecognized. We present a case of a 22-year-old man with multiple manifestations of this disease, including weakness, dizziness, fatigue, tachycardia, abnormal QTc, and orthostasis, which occurred 2 years after his type 1 diabetes diagnosis. He exhibited parasympathetic denervation with resting tachycardia and exercise intolerance but also had evidence of orthostatic hypotension, which suggests sympathetic denervation. He did not have complete cardiovascular autonomic reflex testing, which would have been helpful, but improved with aggressive diabetes treatment and the increase of beta-blockade. It is important to identify these patients to understand their signs and symptoms and consider appropriate therapies.

Inflammation as a Therapeutic Target for Diabetic Neuropathies

Diabetic neuropathies (DNs) are one of the most prevalent chronic complications of diabetes and a major cause of disability, high mortality, and poor quality of life. Given the complex anatomy of the peripheral nervous system and types of fiber dysfunction, DNs have a wide spectrum of clinical manifestations. The treatment of DNs continues to be challenging, likely due to the complex pathogenesis that involves an array of systemic and cellular imbalances in glucose and lipids metabolism. These lead to the activation of various biochemical pathways, including increased oxidative/nitrosative stress, activation of the polyol and protein kinase C pathways, activation of polyADP ribosylation, and activation of genes involved in neuronal damage, cyclooxygenase-2 activation, endothelial dysfunction, altered Na(+)/K(+)-ATPase pump function, impaired C-peptide-related signaling pathways, endoplasmic reticulum stress, and low-grade inflammation. This review summarizes current evidence regarding the role of low-grade inflammation as a potential therapeutic target for DNs.

Resting heart rate and measures of effort-related cardiac autonomic dysfunction predict cardiovascular events in asymptomatic type 2 diabetes

BACKGROUND

Autonomic control of the cardiovascular system may be impaired in type 2 diabetes and is associated with increased morbidity and mortality. Parameters obtained during stress testing may reflect early stages of cardiac autonomic dysfunction and provide prognostic information in asymptomatic type 2 diabetes.

METHODS

We performed maximal exercise treadmill testing in 594 patients with type 2 diabetes without known coronary heart disease. The prognostic significance of physiological parameters associated with autonomic dysfunction was assessed, including chronotropic incompetence (<80% heart rate reserve), abnormal heart rate recovery at 1 minute <18 beats/minute, and resting tachycardia >100 beats/minute. Cox proportional hazards analysis was used to determine the association of exercise parameters with a composite outcome of all-cause mortality, myocardial infarction or stroke.

RESULTS

Resting heart rate >100 beats/minute was observed in 18% of patients, chronotropic incompetence in 30% and heart rate recovery at 1 minute <18 beats/minute in 35%. Over 79 ± 16 months, there were 72 (12%) events. Each parameter was significantly associated with event risk in an adjusted multivariate analysis: chronotropic incompetence (hazard ratio 1.89, 95% confidence interval 1.18-3.01; P = 0.008), resting heart rate ≥100 beats/minute (hazard ratio 1.97, 95% confidence interval 1.19-3.26; P = 0.008) and heart rate recovery at 1 minute <18 beats (hazard ratio 1.77, 95% confidence interval 1.12-2.81; P = 0.015). A progressive relationship between the number of abnormal parameters and event risk was observed (log rank P < 0.001).

CONCLUSIONS

Chronotropic incompetence, resting tachycardia and reduced heart rate recovery are independently and additively associated with long-term mortality, myocardial infarction or stroke in type 2 diabetes without known coronary heart disease.

Effects of exenatide on measures of diabetic neuropathy in subjects with type 2 diabetes: results from an 18-month proof-of-concept open-label randomized study

OBJECTIVE

Experimental studies have reported potential benefit of glucagon-like peptide-1(GLP-1) receptor agonists in preventing diabetic peripheral neuropathy (DPN). We therefore performed a proof-of-concept pilot study to evaluate the effect of exenatide, a GLP-1 agonist, on measures of DPN and cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Forty-six T2D subjects (age 54±10years, diabetes duration 8±5years, HbA1c 8.2±1.3%) with mild to moderate DPN at baseline were randomized to receive either twice daily exenatide (n=22) or daily insulin glargine (n=24). The subjects, with similar HbA1c levels, were followed for 18months. The primary end point was the prevalence of confirmed clinical neuropathy (CCN). Changes in measures of CAN, other measures of small fiber neuropathy such as intra-epidermal nerve fiber density (IENFD), and quality of life were also analyzed.

RESULTS

Glucose control was similar in both groups during the study. There were no statistically significant treatment group differences in the prevalence of CCN, IENFD, measures of CAN, nerve conductions studies, or quality of life indices.

CONCLUSIONS

In this pilot study of patients with T2D and mild to moderate DPN, 18months of exenatide treatment had no significant effect on measures of neuropathy compared with glargine treatment.

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.

Diabetes and cardiac autonomic neuropathy: Clinical manifestations, cardiovascular consequences, diagnosis and treatment

Cardiac autonomic neuropathy (CAN) is a frequent chronic complication of diabetes mellitus with potentially life-threatening outcomes. CAN is caused by the impairment of the autonomic nerve fibers regulating heart rate, cardiac output, myocardial contractility, cardiac electrophysiology and blood vessel constriction and dilatation. It causes a wide range of cardiac disorders, including resting tachycardia, arrhythmias, intraoperative cardiovascular instability, asymptomatic myocardial ischemia and infarction and increased rate of mortality after myocardial infarction. Etiological factors associated with autonomic neuropathy include insufficient glycemic control, a longer period since the onset of diabetes, increased age, female sex and greater body mass index. The most commonly used methods for the diagnosis of CAN are based upon the assessment of heart rate variability (the physiological variation in the time interval between heartbeats), as it is one of the first findings in both clinically asymptomatic and symptomatic patients. Clinical symptoms associated with CAN generally occur late in the disease process and include early fatigue and exhaustion during exercise, orthostatic hypotension, dizziness, presyncope and syncope. Treatment is based on early diagnosis, life style changes, optimization of glycemic control and management of cardiovascular risk factors. Medical therapies, including aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, prostoglandin analogs and alpha-lipoic acid, have been found to be effective in randomized controlled trials. The following article includes the epidemiology, clinical findings and cardiovascular consequences, diagnosis, and approaches to prevention and treatment of CAN.

Perioperative implications of the patient with autonomic dysfunction

PURPOSE OF REVIEW

The autonomic nervous system functions to control heart rate, blood pressure, respiratory rate, gastrointestinal motility, hormone release, and body temperature on a second-to-second basis. Here we summarize some of the latest literature on autonomic dysfunction, focusing primarily on the perioperative implications.

RECENT FINDINGS

The variety of autonomic dysfunction now extends to a large number of clinical conditions in which the cause or effect of the autonomic component is blurred. Methods for detecting dysautonomia can be as simple as performing a history and physical examination that includes orthostatic vital signs measured in both recumbent and vertical positions; however, specialized laboratories are required for definitive diagnosis. Heart rate variability monitoring is becoming more commonplace in the assessment and understanding of autonomic instability. Degenerative diseases of the autonomic nervous system include Parkinson's disease and multiple system atrophy, with the most serious manifestations being postural hypotension and paradoxical supine hypertension. Other conditions occur in which the autonomic dysfunction is only part of a larger disease process, such as diabetic autonomic neuropathy, traumatic brain injury, and spinal cord injury.

SUMMARY

Patients with dysautonomia often have unpredictable and paradoxical physiological responses to various perioperative stimuli. Knowledge of the underlying pathophysiology of their condition is required in order to reduce symptom exacerbation and limit morbidity and mortality during the perioperative period.