Simplified Diagnosis of Cardiovascular Autonomic Neuropathy in Type 2 Diabetes Using Ewing's Battery

Evaluation of Microvascular Complications in Kidney Recipients With Posttransplant Diabetes Mellitus

CONTEXT

The paucity of data on microvascular complications in patients with posttransplant diabetes (PTDM) is an obstacle to developing follow-up algorithms.

OBJECTIVE

To evaluate diabetic microvascular complications in patients with long-standing PTDM.

METHODS

In patients with ≥5-year history of PTDM and age-matched renal transplant recipients without PTDM (NDM), diabetic peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument, the CASE IV device, and in vivo corneal confocal microscopy (CCM). Cardiac autonomic neuropathy tests were performed using heart rate variability. Nephropathy screening was assessed using spot urine albumin/creatinine ratio and eGFR calculation. Diabetic retinopathy was evaluated by fundus examination and photography, and optical coherence tomography.

RESULTS

This study included 41 patients with PTDM and 45 NDM patients. The median follow-up was 107.5 months in the PTDM group. Peripheral neuropathy was significantly higher in the PTDM group than in the NDM group (P = .02). In the PTDM patients with peripheral neuropathy, corneal nerve fiber density examined by CCM was significantly lower than in PTDM patients without neuropathy (P = .001). Parasympathetic involvement was observed in 58.5% of the PTDM group and 22% of the NDM group (P = .001). Sympathetic involvement was present in 65.9% of the PTDM group and 29.3% of the NDM group (P = .001). Retinopathy was observed in 19.5% of patients in the PTDM group and in none of the NDM patients (P < .001). Renal functions were similar between the study groups.

CONCLUSION

Cardiac autonomic neuropathy and diabetic retinopathy can affect patients with PTDM at a high rate. Diabetic retinopathy is a threat to the vision of PTDM patients. Diabetic peripheral neuropathy can be detected early in PTDM patients by CCM.

Effects of Exercise Training on Heart Rate Variability in Healthy Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

This meta-analysis was conducted to investigate the effects of exercise training on heart rate variability (HRV) parameters associated with the autonomic nervous system (ANS) activity. Randomized controlled trials (RCTs) involving healthy adults (aged ≥ 18 years) were included. We searched PubMed, Scopus, Web of Science, and EBSCO databases to identify relevant studies. A random-effects meta-analysis was performed using the standardized mean difference (SMD) and 95% confidence interval (CI). Sixteen RCTs with a total of 623 participants were selected for the final analysis. The analysis showed that exercise training improved the standard deviation of normal-to-normal intervals (SDNN) (SMD: 0.58 (0.16, 1.00); p = 0.007), the root mean square of successive differences in heart period series (RMSSD) (SMD: 0.84 (0.36, 1.31); p = 0.0005), and the absolute power of high-frequency band (HF) (SMD: 0.89 (0.27, 1.51); p = 0.005) parameters compared to the control group. Analysis of the moderator variables showed that the effect of exercise on HRV indices may be influenced by sex, age, and type of exercise used, specifically in HF band, absolute power of low-frequency band (LF), and LF/HF ratio parameters. Despite the limited number of existing RCTs related to the subject, the results suggest that exercise training enhances HRV parameters associated with vagal-related activity (RMSSD and HF) and both sympathetic and parasympathetic activities (SDNN). This study overcomes the lack of meta-analyses on the effects of exercise training on autonomic modulation among healthy adults and may bridge the gap in understanding the potential physiological underpinnings of the acknowledged positive health benefits of exercise.

Evaluating treatment options for cardiovascular autonomic neuropathy in patients with diabetes mellitus: a systematic review

Background

Cardiovascular autonomic neuropathy (CAN) is a debilitating complication of diabetes mellitus. To date, there is no systematic review on all the available drug treatments for CAN in diabetic patients, except for one review focusing on aldose reductase inhibitors.

Objective

To evaluate available drug treatment options for CAN in diabetic patients.

Methods

A systematic review was conducted with a search of CENTRAL, Embase, PubMed and Scopus from database inception till 14th May 2022. Randomised controlled trials (RCTs) of diabetic patients with CAN that investigated the effect of treatment on blood pressure, heart rate variability, heart rate or QT interval were included.

Results

Thirteen RCTs with a total of 724 diabetic patients with CAN were selected. There was a significant improvement in the autonomic indices of diabetic patients with CAN given angiotensin-converting enzyme inhibitor (ACEI) for 24 weeks (p<0.05) to two years (p<0.001), angiotensin-receptor blocker (ARB) for one year (p<0.05), single dose of beta blocker (BB) (p<0.05), omega-3 polyunsaturated fatty acids (PUFAs) for three months (p<0.05), alpha-lipoic acid (ALA) for four months (p < 0.05) to six months (p=0.048), vitamin B12 in combination with ALA, acetyl L‑carnitine (ALC), superoxide dismutase (SOD) for one year (p=0.001)  and near significant improvement in the autonomic indices of diabetic patients with CAN given vitamin E for four months (p = 0.05) compared to the control group. However, there was no significant improvement in the autonomic indices of patients given vitamin B12 monotherapy (p ≥ 0.05).

Conclusion

ACEI, ARB, BB, ALA, omega-3 PUFAs, vitamin E, vitamin B12 in combination with ALA, ALC and SOD could be effective treatment options for CAN, while vitamin B12 monotherapy might be unlikely to be recommended for the treatment of CAN due to its lack of efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00629-x.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cardiovascular autonomic neuropathy and incident diabetic kidney disease in patients with type 2 diabetes

AIMS

We investigated the association between cardiovascular autonomic neuropathy (CAN) and incident diabetic kidney disease (DKD).

METHODS

This retrospective longitudinal study included 2,033 patients with type 2 diabetes (mean age 57.2 years, 57.4% male, and median diabetes duration 8.0 years), free of renal dysfunction or cardiovascular disease at initiation. Cardiovascular autonomic reflex tests were performed once at baseline, and CAN was defined as ≥ 2 abnormal parasympathetic test results. Urine ACR and eGFR were concurrently measured at baseline and every 3-6 months thereafter. Incident DKD was defined as the development of ACR ≥ 30 mg/g at two or more follow-up examinations or eGFR < 60 ml/min/1.73 m² with ≥ 25% decrease from baseline.

RESULTS

During a median follow-up of 2.9 years (1.1 - 4.8), 290 (14.3%) patients developed DKD, comprising 79.7% (N = 231) cases of new-onset albuminuria alone, 14.5% (N = 42) cases of eGFR decline alone, and 5.8% (N = 17) cases of both. Compared to those without CAN, patients with CAN had a significantly higher risk of incident DKD in a multivariable Cox regression model (HR 1.56, 95% CI 1.15 - 2.12; P = 0.005).

CONCLUSION

CAN is may be a useful marker for long-term complications including DKD in patients with type 2 diabetes. Monitoring of CAN helps to identify high risk patients of future renal impairment.

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.

Two-Year Responses of Heart Rate and Heart Rate Variability to First Occupational Lead Exposure

[Figure: see text].

Correlation of staging and risk factors with cardiovascular autonomic neuropathy in patients with type II diabetes mellitus

The impairment of cardiovascular autonomic control among the underdiagnosed complication of diabetes mellitus (DM) with a high prevalence rate of up to 60% in type 2 DM (T2DM). Cardiac autonomic neuropathy (CAN) is an independent risk factor for cardiovascular mortality, arrhythmia, silent ischemia, any major cardiovascular event, and heart failure. We aimed to evaluate cardiovascular autonomic activity by different physiological maneuvers, study risk factors for diabetic CAN including age, gender, duration of diabetes, body mass index (BMI), and glycemic control, and correlate CAN stage with risk factors. One hundred and forty-two T2DM patients consisted of 62 males and 80 females and 100 volunteers as a control sample. Cardiac autonomic functions were assessed by Ewing's tests. Glycated hemoglobin (HbA1c), body weight, height, body mass index (BMI), and waist-hip ratio (WHR) were also measured. Cardiovascular autonomic functions and Ewing scores were significantly different in people with diabetes when compared with control healthy subjects. Ewings test values and Ewing scores were significantly different between diabetics with and without CAN and within patients with different CAN staging. People with diabetes with CAN have a significantly longer duration of disease when compared to those without CAN. A strong association has been found between CAN severity and patient age, duration of disease, HbA1c severity, and the WHR (P < 0.001) but not with BMI. The duration of disease and HbA1c level appear to be associated with the development of CAN (P = 0.001 and P = 0.008, respectively). The poorer glycemic control and the longer the duration of the disease, the higher the prevalence of CAN in T2DM. Age, duration of disease, WHR, and HbA1c are well correlated with the severity of CAN. Parasympathetic impairment is more sensitive to the detection of autonomic dysfunctions than do sympathetic impairment.

Peripheral Nerve Conduction And Sympathetic Skin Response Are Reliable Methods to Detect Diabetic Cardiac Autonomic Neuropathy

AIM

This study aimed to investigate the role of nerve conduction studies (NCS) and sympathetic skin response (SSR) in evaluating diabetic cardiac autonomic neuropathy (DCAN).

METHODS

DCAN was diagnosed using the Ewing test combined with heart rate variability analysis. NCS and SSR were assessed by electrophysiological methods. The association between NCS/SSR and DCAN was assessed via multivariate regression and receiver-operating characteristic analyses.

RESULTS

The amplitude and conduction velocity of the motor/sensory nerve were found to be significantly lower in the DCAN+ group (all P < 0.05). A lower amplitude of peroneal nerve motor fiber was found to be associated with increased odds for DCAN (OR 2.77, P < 0.05). The SSR amplitude was lower while the SSR latency was longer in the DCAN+ group than in the DCAN- group. The receiver-operating characteristic analysis revealed that the optimal cutoff points of upper/lower limb amplitude of SSR to indicate DCAN were 1.40 mV (sensitivity, 61.9%; specificity, 66.3%, P < 0.001) and 0.85 mV (sensitivity, 66.7%; specificity, 68.5%, P < 0.001), respectively. The optimal cutoff points of upper/lower limb latency to indicate DCAN were 1.40 s (sensitivity, 61.9%; specificity, 62%, P < 0.05) and 1.81 s (sensitivity, 69.0%; specificity, 52.2%, P < 0.05), respectively.

CONCLUSIONS

NCS and SSR are reliable methods to detect DCAN. Abnormality in the peroneal nerve (motor nerve) is crucial in predicting DCAN. SSR may help predict DCAN.

Computerized dynamic pupillometry as a screening tool for evaluation of autonomic activity

OBJECTIVES

Dynamic pupillometry is a simple screening tool for quantifying pupillary light reflex (PLR), to indicate autonomic nervous system (ANS) activity. Heart rate variability (HRV) is the gold standard method for assessing ANS effects on the heart. The present study aimed to compare ANS activity as measured using dynamic pupillometry (DP) with short term HRV in healthy volunteers.

METHODS

The study includes 200 participants aged between 20-60 years. PLR was measured using infrared videography and categorized into different quantitative parameters that reflect ANS activity. Simultaneously, Lead II ECG was recorded for 5 min to evaluate the short term HRV of time and frequency domain parameters. The data obtained from the two methods were compared with each other to provide the relationship between PLR and HRV.

RESULTS

Study participants' mean age was 36.95 ± 9.45 years. The different pupillary indices of PLR and all the HRV parameters were within the range of normative data. Several PLR indicators of the parasympathetic function include mean constriction velocity (MCV; r = 0.60, P < 0.001), absolute constriction amplitude (ACA; r = 0.57, P < 0.001) baseline pupil diameter (BPD; r = 0.44, p < 0.001), and minimum pupil diameter (MPD; r = -0.35, p < 0.001) were significantly correlated with high-frequency power (HF in normalized units) of HRV signal.

CONCLUSION

PLR variables showed a significant relationship to HRV indices. Dynamic pupillometry can be a complementary tool to HRV for evaluating ANS activity.

Clinical Tools for Peripheral Neuropathy to Exclude Cardiovascular Autonomic Neuropathy in Type 2 Diabetes Mellitus

INTRODUCTION

Assessment for cardiovascular autonomic neuropathy (CAN) remains difficult in everyday clinical practice. We sought to examine the diagnostic utility of various simple tools for diabetic peripheral neuropathy (DPN) in the detection of CAN in type 2 diabetes mellitus.

METHODS

We examined 153 type 2 diabetes mellitus subjects by various DPN tools (vibration perception threshold, 10 g Semmes-Weinstein monofilament, Ipswich touch test, NC-stat^®/DPNCheck, neuropathy disability score) for the detection of CAN. CAN was diagnosed by the standardised cardiovascular autonomic reflex function tests.

RESULTS

For the diagnosis of CAN, assessment of small nerve fibre function (pinprick sensation, temperature perception) yielded a very high negative predictive value (97%), with high sensitivity (89%) and moderate specificity (73%). The vibration perception threshold was second in diagnostic utility (91% negative predictive value, 62% sensitivity and 75% specificity).

CONCLUSIONS

Based on their high negative predictive value, simple tools for DPN may prove useful to exclude CAN in type 2 diabetes mellitus. These encouraging results merit further evaluation to enable wider screening for CAN.

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%.

Correlation of cardiac autonomic neuropathy with small and large peripheral nerve function in type 2 diabetes mellitus

AIMS

To analyse the correlation of cardiac autonomic neuropathy (CAN), sympathetic and parasympathetic dysfunction with the different diagnostic tools for large and small peripheral nerve fibres in type 2 diabetes mellitus (T2DM).

METHODS

We included 153 T2DM subjects (92 men) with mean age of 64.4 years. CAN, as well as sympathetic and parasympathetic dysfunction were diagnosed by the Ewing's cardiovascular reflex tests. Vibration perception threshold (VPT), monofilament, Ipswich Touch test, automated sural nerve conduction study and neuropathy disability score (NDS) evaluated large and small peripheral nerve fibre function.

RESULTS

CAN (adjusted odds ratio [aOR]: 44.57), parasympathetic (aOR: 18.40) and sympathetic dysfunction (aOR: 5.50) correlated with measures of small fibre function evaluated by pinprick sensation and temperature perception. Among tools for large nerve fibres, positive correlation was shown between: (1) CAN and abnormal VPT (aOR: 16.78), (2) parasympathetic dysfunction and abnormal VPT (aOR: 39.47).

CONCLUSIONS

CAN and parasympathetic dysfunction correlate with peripheral neuropathy, especially when the latter is assessed through VPT and measures of small fibre function as evaluated by pinprick sensation and temperature perception. The latter additionally correlate with sympathetic nervous system impairment.

Update on the Impact, Diagnosis and Management of Cardiovascular Autonomic Neuropathy in Diabetes: What Is Defined, What Is New, and What Is Unmet

The burden of diabetic cardiovascular autonomic neuropathy (CAN) is expected to increase due to the diabetes epidemic and its early and widespread appearance. CAN has a definite prognostic role for mortality and cardiovascular morbidity. Putative mechanisms for this are tachycardia, QT interval prolongation, orthostatic hypotension, reverse dipping, and impaired heart rate variability, while emerging mechanisms like inflammation support the pervasiveness of autonomic dysfunction. Efforts to overcome CAN under-diagnosis are on the table: by promoting screening for symptoms and signs; by simplifying cardiovascular reflex tests; and by selecting the candidates for screening. CAN assessment allows for treatment of its manifestations, cardiovascular risk stratification, and tailoring therapeutic targets. Risk factors for CAN are mainly glycaemic control in type 1 diabetes mellitus (T1DM) and, in addition, hypertension, dyslipidaemia, and obesity in type 2 diabetes mellitus (T2DM), while preliminary data regard glycaemic variability, vitamin B12 and D changes, oxidative stress, inflammation, and genetic biomarkers. Glycaemic control prevents CAN in T1DM, whereas multifactorial intervention might be effective in T2DM. Lifestyle intervention improves autonomic function mostly in pre-diabetes. While there is no conclusive evidence for a disease-modifying therapy, treatment of CAN manifestations is available. The modulation of autonomic function by SGLT2i represents a promising research field with possible clinical relevance.

Cardiovascular reflex tests in patients with systemic lupus erythematosus: clinical performance and utility

Background

This review summarizes current knowledge about cardiovascular reflex tests (CVRTs) and other selected autonomic nervous system (ANS) assessment tests in systemic lupus erythematosus (SLE) patients and assesses their clinical utility in this group of patients.

Methods

The PubMed database was searched for terms associated with CVRTs and SLE. Only papers available in full text and published in English were considered. Ultimately, 13 were selected and analyzed.

Results

In most of the studies CVRTs results were reported more likely to be abnormal in patients with SLE when compared with controls. The reported prevalence of ANS dysfunction in SLE, diagnosed using CVRTs, ranged from 23.5% to 82.7% of patients, likely because of different definitions of ANS dysfunction, variability in methods of performing CVRTs, and potential confounding factors. In general CVRTs results did not correlate with SLE activity or disease duration, but some CVRTs results correlated with some peptides associated with ANS function, including neuropeptide Y and vasoactive intestinal peptide.

Conclusion

Patients with SLE generally have abnormal or borderline results of CVRTs, which indicate prevalent abnormalities of the ANS in SLE. Performance of CVRTs requires good standardization of test conditions and familiarity with the proper administration and interpretation of these tests.

Autonomic Neuropathy-a Prospective Cohort Study of Symptoms and E/I Ratio in Normal Glucose Tolerance, Impaired Glucose Tolerance, and Type 2 Diabetes

Background

Autonomic neuropathy in diabetes, in addition to causing a range of symptoms originating from the autonomic nervous system, may increase cardiovascular morbidity. Our aim was to study the progression of autonomic neuropathy, based on symptom score and evaluation of an autonomic test, in persons with normal and impaired glucose tolerance and in patients with type 2 diabetes (T2D).

Methods

Participants were recruited in 2003/2004 with a follow-up in 2014. The participants’ glucose tolerance was categorized using oral glucose tolerance tests. Symptoms were evaluated using an autonomic symptom score (ASS), ECG was used to test cardiac autonomic function based on the expiration/inspiration ratio (E/I ratio), and blood samples were taken on both occasions.

Results

ASSs were higher at follow-up in the T2D patients than in the normal glucose tolerance group (mean 1.21 ± 1.30 vs. 0.79 ± 0.7; p < 0.05). E/I ratio did not deteriorate more than could be expected as an aging effect in well-controlled T2D. No relationship was found between E/I ratio and HbA1c or ASS.

Conclusion

The presence of autonomic symptoms increased over time in T2D patients, but the symptoms did not correlate with the E/I ratio in this metabolically well-controlled cohort. ASSs can be a useful clinical tool when assessing the progression of autonomic dysfunction in patients with abnormal glucose metabolism.

Cardiac vagal tone, a non-invasive measure of parasympathetic tone, is a clinically relevant tool in Type 1 diabetes mellitus

AIMS

To compare a novel index of parasympathetic tone, cardiac vagal tone, with established autonomic variables and to test the hypotheses that (1) cardiac vagal tone would be associated with established time and frequency domain measures of heart rate and (2) cardiac vagal tone would be lower in people with Type 1 diabetes than in a matched healthy cohort and lower still in people with established neuropathy.

METHODS

Cardiac vagal tone is a validated cardiometrically derived index of parasympathetic tone. It is measured using a standard three-lead electrocardiogram which connects, via Bluetooth, to a smartphone application. A 5-min resting recording of cardiac vagal tone was undertaken and observational comparisons were made between 42 people with Type 1 diabetes and peripheral neuropathy and 23 without peripheral neuropathy and 65 healthy people. In those with neuropathy, 24-h heart rate variability values were compared with cardiac vagal tone. Correlations between cardiac vagal tone and clinical variables were also made.

RESULTS

Cardiac vagal tone was lower in people with established neuropathy and Type 1 diabetes in comparison with healthy participants [median (interquartile range) linear vagal scale 3.4 (1.6-5.5 vs 7.0 (5.5-9.6); P < 0.0001]. Cardiac vagal tone was positively associated with time (r = 0.8, P < 0.0001) and frequency domain markers of heart rate variability (r = 0.75, P < 0.0001), representing established measures of parasympathetic function. Cardiac vagal tone was negatively associated with age (r=-0.32, P = 0.003), disease duration (r=-0.43, P < 0.0001) and cardiovascular risk score (r=-0.32, P = 0.006).

CONCLUSIONS

Cardiac vagal tone represents a convenient, clinically relevant method of assessing parasympathetic nervous system tone, potentially facilitating the earlier identification of people with Type 1 diabetes who should undergo formal autonomic function testing.

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.