Cardiac autonomic neuropathy in diabetes: comparison of measures of R-R interval variation

Hyperglycemia: A determinant of cardiac autonomic dysfunction in youth with obesity across the spectrum of glycemic regulation

OBJECTIVES

To characterize the determinants of heart rate variability (HRV) in youth with obesity across the glycemia spectrum.

METHODS

A total of 94 adolescents, 15 ± 2.1 years (21 with normal weight, 23 with overweight-normal glucose tolerance, 26 with prediabetes and 24 with type 2 diabetes [T2D]) underwent an assessment of body composition (dual-energy x-ray absorptiometry), 2-h oral glucose tolerance test with the calculation of indices of glycemia and insulin sensitivity (IS), inflammatory markers (high-sensitivity C-reactive protein [hs-CRP] and tumour necrosis factor-α [TNF-α]), and HRV by peripheral arterial tonometry.

RESULTS

The HRV frequency-domain index (low-frequency to high-frequency ratio [LF/HF]), an estimate of the ratio between sympathetic and parasympathetic activity, increased across the glycemic spectrum, and was highest in T2D compared with the other three groups (p = 0.004). LF/HF correlated with %body fat (r = 0.22, p = 0.04); fasting (r = 0.39, p < 0.001), 2-h (r = 0.31, p = 0.004), and area under the curve glucose (r = 0.32, p = 0.003); hs-CRP (r = 0.33, p = 0.002) and TNF-α (r = 0.38, p = 0.006). In a linear regression model, fasting glucose (β = 0.39, p = 0.003) and hs-CRP (β = 0.21, p = 0.09) contributed to the variance in Ln LF/HF independent of IS, %body fat, age, sex, race-ethnicity and Tanner stage (R2  = 0.23, p = 0.013).

CONCLUSIONS

Youth with impaired glucose regulation have evidence of cardiac autonomic dysfunction with decreased HRV, and sympathetic overdrive (increased LF/HF). This dysfunction is mainly related to glycemia and systemic inflammation.

Acute Changes in Heart Rate Variability to Glucose and Fructose Supplementation in Healthy Individuals: A Double-Blind Randomized Crossover Placebo-Controlled Trial

Simple Summary

In this study, we investigated the cardio-autonomic stress responses to the ingestion of liquid glucose, fructose, a combination thereof and a placebo in healthy individuals at rest. The cardio-autonomic response was more pronounced in all groups with carbohydrates compared to placebo indicating an increased cardio-autonomic stress response resulting in a reduced heart-rate variability. When investigating different levels of blood glucose, the findings showed a significant decline in heart-rate variability with increasing blood glucose levels. This was also seen with severely low levels of blood glucose. The speed of how quick blood glucose increased and decreased also impacted the cardio-autonomic response which further deteriorated heart-rate variability. These findings indicate that healthy human’s autonomic system responds quickly to changes in their blood glucose.

Abstract

Background: It is unknown how different types of carbohydrates alter the cardio-autonomic system in healthy individuals. Therefore, the aim of this study was to investigate how heart-rate variability changes to single dose ingestion of glucose, fructose, glucose and fructose, and an artificial sweetener (sucralose). Methods: In a double-blind randomized crossover placebo-controlled setting, 15 participants received all study-specific substances in liquid form. During each 2-h visit, venous blood glucose was measured in a 5-min interval while heart-rate variability was measured continuously via Holter-electrocardiograph. Results: Ingestion of different types of carbohydrates and sucralose showed significant differences for heart rate (p < 0.001), SDNN (p < 0.008), RMSSD (p < 0.001), pNN50 (p < 0.001) and blood pressure (p < 0.001). Different glucose levels significantly altered parameters of heart-rate variability and blood pressure (all p < 0.001), while the rate of change in blood glucose led to changes in heart rate variability, but not in heart rate (p = 0.25) or blood pressure (p = 0.99). Conclusions: Ingestion of different types of carbohydrates lead to reductions in heart-rate variability compared to a placebo. Blood glucose values above or below 70–90 mg/dL decreased heart rate variability while this was also seen for rapid glucose changes, yet not as pronounced. Healthy individuals should be conscious about carbohydrate intake while maintaining blood glucose levels between 70–90 mg/dL.

Cardiac autonomic neuropathy in fibromyalgia: Revisited

BACKGROUND

Fibromyalgia (FM) is associated with widespread autonomic dysfunction where sympathetic predominance explains associated complaints such as widespread pain, sleep disorders and anxiety. Recent studies indicate a possible neurovascular autonomic interaction in the pathogenesis of FM.

OBJECTIVE

Our study paradigm included a modified Ewing's battery of autonomic function tests to find the cardiac autonomic neuropathy (CAN) in FM patients. The battery comprises some tests such as the Valsalva maneuver, which are effort-dependent, so we also aimed to identify a potential simplified test out of the whole battery as an index marker of CAN in FM patients.

METHODS

Forty-two female patients with FM were included in this study and were administered sympathetic and parasympathetic reactivity tests to explore the presence of CAN. We compared the results from each sympathetic and parasympathetic reactivity test against CAN.

RESULTS

Delta heart rate in the deep breathing test was significantly different in patients with and without CAN. Delta heart rate also exhibited best diagnostic performance (AUC = 0.769, 95% CI: 0.619-0.920, p< 0.001), with 88% sensitivity, 64% specificity, and 89% negative predictive value (NPV). The 30: 15 ratio during the lying to standing test also emerged as a suitable index; however it did not show any difference between CAN and non-CAN patients.

CONCLUSION

The delta heart rate has the best diagnostic accuracy, primarily in CAN's exclusion by its very high sensitivity and NPV.

Decline in renal function associated with cardiovascular autonomic neuropathy positively coordinated with proteinuria in patients with type 2 diabetes

AIMS/INTRODUCTION

To investigate the association between cardiovascular autonomic neuropathy (CAN) assessed by the coefficient of variation of the R-R interval and the reduction in the estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

MATERIALS AND METHODS

This retrospective observational cohort study enrolled type 2 diabetes patients who had their coefficient of variation of the R-R interval measured on an electrocardiogram from January 2005 to December 2018. CAN was defined using the reference coefficient of variation of the R-R interval value based on age and sex. The primary outcome was set as a 40% eGFR decline from baseline. Regression analyses using the Cox proportional hazards model were carried out to evaluate the association.

RESULTS

Of the 831 patients, 118 (14.2%) were diagnosed with CAN. In the analysis of the primary outcome, the median follow-up period was 5.3 years, and 25 (21.2%) patients with CAN and 78 (10.9%) patients without CAN developed a 40% eGFR decline. In the univariate regression analysis, CAN was significantly associated with a 40% eGFR decline (hazard ratio 2.42, 95% confidence interval 1.54-3.80). In the multivariate analysis, CAN remained almost significant after adjusting for the prognostic risk factors for CAN and the decline in the renal function, and an interaction with proteinuria was found. In analyses for the interaction effect between CAN and proteinuria, the presence of CAN synergistically increased the risk of an eGFR decline in patients with macroproteinuria.

CONCLUSIONS

CAN strongly increased the risk of a 40% eGFR decline from baseline, especially in type 2 diabetes patients with macroproteinuria.

Evaluation of the Degree of Agreement of Four Methods for Diagnosing Diabetic Autonomic Neuropathy

Background: There are many methods to diagnose diabetic autonomic neuropathy (DAN); however, often, the various methods do not provide consistent results. Even the two methods recommended by the American Diabetes Association (ADA) guidelines, Ewing's test and heart rate variability (HRV), sometimes give conflicting results. The purpose of this study was to evaluate the degree of agreement of the results of the Composite Autonomic Symptom Score 31 (COMPASS-31), skin sympathetic reaction (SSR) test, Ewing's test, and HRV in diagnosing DAN.

Methods: Patients with type 2 diabetes were recruited and each received the COMPASS-31, SSR, Ewing's test, and HRV for the diagnosis of DAN. Patients were categorized as DAN(+) and DAN(–) by each of the tests. Kappa consistency tests were used to evaluate the agreement of diagnosing DAN between any two methods. Spearman's correlation test was used to evaluate the correlations of the severity of DAN between any two methods. Receiver operating characteristic (ROC) analyses were used to evaluate the diagnostic value and the cutoff value of each method.

Results: A total of 126 type 2 diabetic patients were included in the study. The percentages of DAN(+) results by HRV, Ewing's test, COMPASS-31, and SSR were 61, 40, 35, and 33%, respectively. COMPASS-31 and Ewing's test had the best agreement for diagnosing DAN (κ = 0.512, p < 0.001). COMPASS-31 and Ewing's test also had the best correlation with respect to the severity of DAN (r = 0.587, p < 0.001). Ewing's test and COMPASS-31 had relatively good diagnostic values (AUC = 0.703 and 0.630, respectively) in the ROC analyses.

Conclusions: COMPASS-31 and Ewing's test exhibit good diagnostic consistency and severity correlation for the diagnosis of DAN. Either test is suitable for the diagnosis of DAN and treatment follow-up.

Predictive value of heart rate deceleration capacity on coronary artery lesion in acute phase of Kawasaki disease

This study was to investigate the correlation of vagal activity with coronary artery lesion (CAL) in Kawasaki disease (KD) children, and assess the predictive value of heart rate deceleration capacity (DC) for CAL in acute phase of KD.50 KD children with CAL, 130 KD children without CAL, 30 children with acute upper respiratory infection and 100 healthy children were recruited and indicators reflecting vagal activity including DC were measstuogram. KD children with CAL showed decreased vagal activity with significantly lower values of DC. DC was negatively correlated with levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and C-reactive protein (CRP) in KD children. DC was a usable cardiac electrophysiological index to predict CAL in children with KD, with an area under the receiver operating characteristic curve (AUC) of 0.741. The cut-off value of DC for predicting CAL in KD children was 4.37 ms. DC was an independent predictor of CAL in children with KD, evaluated by multiple logistic regression analysis, KD children with DC ≤ 4.37 ms had an increased risk of CAL, with odds ratios (OR) of 5.94. Our study illustrates DC could be used to predict CAL in acute phase of KD.

Co-Existence of hypertension worsens post-exercise cardiac autonomic recovery in type 2 diabetes

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a commonly overlooked complication of Type 2 Diabetes Mellitus (T2DM) characterized by imbalance between sympathetic and parasympathetic supply to the heart. The susceptibility of heart to dysrhythmias and fatal events increases during and after exercise due to a shift in autonomic regulation. Diabetes and hypertension (HTN) frequently occur concurrently and both conditions lead to impaired cardiac autonomic control. However, their impact together on post-exercise autonomic recovery remains to be explored.

OBJECTIVE

The objective of the study was to investigate the effect of co-existence of HTN on cardiac autonomic recovery (assessed by heart rate recovery and heart rate variability) in patients with T2DM.

METHODS

Forty eight type 2 diabetic patients (24 normotensive, 24 hypertensive), 24 non-diabetic patients with essential HTN, and 27 healthy controls, were recruited into the study and assessed for heart rate recovery (HRR) following a graded maximal test. Also, heart rate variability (HRV) was recorded before and following the bout of maximal exercise.

RESULTS

Heart rate recovery at 1 (HRR1min) and 2 (HRR2min) minute(s) showed significant effects for DM (p < 0.001) and HTN (p < 0.001), while DM × HTN interaction was found to be non-significant. Resting HRV showed a significant decline in time-domain variables for the DM group (p < 0.01). Recovery of HRV showed a significant effect of time (p < 0.05) for all indices, the group effect was found significant only for time-domain measures (p < 0.05).

CONCLUSION

Both HRR and HRV recovery were impaired in DM and HTN. Moreover, the co-existence of HTN had a synergistic effect, causing further worsening of autonomic recovery in T2DM.

The cardiac autonomic nervous system response to different daily demands among patients at the sub-acute phase post ischemic stroke and healthy controls

BACKGROUND

Autonomic disturbances are a common phenomenon in patients' post-stroke, characterized by hypo function of the para-sympathetic and/or overactive sympathetic system. The impact of autonomic disturbances on physical therapy tasks during the rehabilitation period has not yet been assessed.

OBJECTIVE

To describe the response of the cardiac autonomic nervous system during different tasks, among patients and age-matched healthy controls.

METHODS

Nineteen patients in the subacute phase post first-ever ischemic stroke, and 16 controls. The Polar advanced heart rate monitor (RS800CX) was used to record RR intervals at rest, during paced breathing exercise, while performing different types of muscle contractions, and during single and dual task conditions.

RESULTS

RR intervals and heart-rate variability (HRV) parameters were significantly lower among patients post stroke, both at rest and during most of the activities tested. Among the control group a significant autonomic adaptation was seen in the form of reduced RR intervals and HRV during muscle contraction and a significant increase in these parameters during slow breathing, no significant changes were observed among patients post stroke.

CONCLUSION

Patients post-stroke experience hyper sympathetic function at rest and less adaptive cardiac autonomic control during different activities, which all may have an impact on rehabilitation outcomes.

Autonomic Dysfunction Predicts Clinical Outcomes After Acute Ischemic Stroke: A Prospective Observational Study

BACKGROUND AND PURPOSE

Central autonomic dysfunction increases stroke morbidity and mortality. We aimed to investigate whether poststroke autonomic dysfunction graded by Ewing battery can predict clinical outcome.

METHODS

In this prospective observational study, we assessed autonomic function of ischemic stroke patients within 7 days from symptom onset by Ewing battery. On the basis of the magnitude of autonomic dysfunction, we stratified patients into significant (definite, severe, or atypical) or minor (normal or early) autonomic function impairment groups and correlated the impairment with the 3-month modified Rankin Scale score (good outcome: modified Rankin Scale score 0≈2; poor outcome: modified Rankin Scale score 3≈6).

RESULTS

Among the 150 patients enrolled (mean age, 66.4±9.9 years; 70.7% males), minor autonomic dysfunction was identified in 36 patients (24.0%), and significant autonomic dysfunction was identified in 114 patients (76.0%) based on Ewing battery. In 3 months, a poor functional outcome was found in 32.5% of significant group patients compared with 13.9% in the minor group (P=0.031). Crude odds ratios of the magnitude of autonomic dysfunction and 3-month unfavorable functional outcome after acute ischemic stroke were 2.979 (95% confidence interval, 1.071-8.284; P=0.036). After adjusting for confounding variables with statistical significance between the 2 functional outcome subgroups identified in univariate analysis (including sex and National Institutes of Health Stroke Scale score on admission), the magnitude of autonomic dysfunction still independently predicted an unfavorable outcome, with an odds ratio of 3.263 (95% confidence interval, 1.141-9.335; P=0.027).

CONCLUSIONS

Autonomic dysfunction gauged by Ewing battery predicts poor functional outcome after acute ischemic stroke.

A NEW METHOD FOR AUTOMATED DETECTION OF DIABETES FROM HEART RATE SIGNAL

Diabetes Mellitus (DM) is a chronic disease and it is characterized based on the increase in the sugar level in the blood. The other diseases such as the cardiomyopathy, neuropathy and retinopathy may occur due to the DM pathology. The RR-time series or heart rate (HR) signal quantifies the beat-to-beat variations in the electrocardiogram (ECG) and it has been widely used for the detection of various cardiac diseases. Detection of DM based on the features of HR signal is a challenging problem. This paper copes with a new method for the detection of Diabetes Mellitus (DM) based on the features extracted from the HR signal. The Singular Spectrum Analysis (SSA) of HR signal and the Kernel Sparse Representation Classifier (KSRC) are the mathematical foundations used to achieve the detection. SSA is used to decompose the HR signal into sub-signals, and diagnostic features such as the maximum value of each sub-signal and eigenvalues are evaluated. Then, the KSRC uses the proposed diagnostic features as inputs for detecting diabetes. The experimental results reveal that the proposal attains the accuracy, sensitivity, and specificity values of 92.18%, 93.75% and 90.62%, respectively, employing the KSRC and the hold-out cross-validation approach. The method is compared with existing approaches for detecting diabetes from HR signal.

Association between cardiac autonomic control and cognitive performance among patients post stroke and age-matched healthy controls-an exploratory pilot study

Associations between autonomic nervous system health and cognitive performance have been described in different populations. Autonomic disturbances are a common phenomenon in patients post stroke. Little is known about the relationship between post stroke disturbances of the autonomic nervous system and the commonly occurring disturbances of cognitive functions revealed by victims of stroke. To assess the association between heart rate variability (HRV) and cognitive performance among patients post ischemic stroke and healthy age-matched controls, 13 patients post first-ever ischemic stroke aged 40-80 years and 15 age-matched healthy controls were evaluated. HRV was monitored during sustained handgrip, while breathing at a rate of six breaths per minute, while performing the serial-3 subtraction task sitting at rest, and while cycling. Patients post stroke had greater error rate in the serial-3 subtraction task, and lower HRV (both at rest and during task performance) relative to healthy controls (at rest 26 ms [10-53] vs. 43 ms [29-88]). The HRV of stroke patients showed less sensitivity to changes in testing conditions, and also failed to show the correlation with cognitive performance exhibited by the healthy subjects. Stroke patients experience autonomic nervous system dysfunction in parallel to their motor and cognitive impairments. Too often only the latter receive appropriate treatment consideration in the rehabilitation setting. The current results, and earlier research, point to the importance of focusing clinical attention to the status of the autonomic nervous system, as amelioration of its functioning is likely to enhance motor and cognitive functioning as well.

Association of Diabetes Related Complications with Heart Rate Variability among a Diabetic Population in the UAE

Microvascular, macrovascular and neurological complications are the key causes of morbidity and mortality among type II diabetes mellitus (T2DM) patients. The aim of this study was to investigate the alterations of cardiac autonomic function of diabetic patients in relation to three types of diabetes-related complications. ECG recordings were collected and analyzed from 169 T2DM patients in supine position who were diagnosed with nephropathy (n = 55), peripheral neuropathy (n = 64) and retinopathy (n = 106) at two hospitals in the UAE. Comparison between combinations of patients with complications and a control diabetic group (CONT) with no complication (n = 34) was performed using time, frequency and multi-lag entropy measures of heart rate variability (HRV). The results show that these measures decreased significantly (p<0.05) depending on the presence and type of diabetic complications. Entropy, (median, 1st- 3rd interquartile range) for the group combining all complications (1.74,1.37-2.09) was significantly lower than the corresponding values for the CONT group (1.77, 1.39-2.24) with lag-1 for sequential beat-to-beat changes. Odds ratios (OR) from the entropy analysis further demonstrated a significantly higher association with the combination of retinopathy and peripheral neuropathy versus CONT (OR: 1.42 at lag 8) and an even OR for the combination of retinopathy and nephropathy (OR: 2.46 at lag 8) compared to the other groups with complications. Also, the OR of low frequency power to high frequency power ratio (LF/HF) showed a higher association with these diabetic-related complications compared to CONT, especially for the patient group combining all complications (OR: 4.92). This study confirms that the type of microvascular or peripheral neuropathy complication present in T2DM patients have different effects on heart rate entropy, implying disorders of multi-organ connectivity are directly associated with autonomic nervous system dysfunction. Clinical practice may benefit from including multi-lag entropy for cardiac rhythm analysis in conjunction with traditional screening methods in patients with diabetic complications to ensure better preventive and treatment outcomes in the Emirati Arab population.

Short-Term Effect of Physical Exercise at Lactate Threshold on Choice Reaction Time

The duration of the enhancement of choice reaction task efficiency by physical exercise at lactate threshold was studied. After healthy male students completed the exercise or nonexercise (control) period for 10 min., they performed a three-choice reaction task for 20 min. The mean heart rate during the choice reaction task after the exercise was higher than that after the control period ( p<.05). For average percentage of correct answers, there were no significant differences between the exercise and control conditions. The reaction time during the first 8 min. of the 20-min. choice reaction task after the exercise period was less than that after the control period and increased gradually thereafter. In conclusion, whereas the choice reaction time was improved by physical exercise at around lactate threshold, the positive effects were seen mainly in the early stages of the task.

Autonomic dysfunction in first ever ischemic stroke: Prevalence, predictors and short term neurovascular outcome

OBJECTIVES

Central autonomic dysfunction(AD) is reported post-stroke. Very few studies have looked at its impact on neurovascular outcome. We sought to study the prevalence and predictors of autonomic dysfunction in patients with first ever acute ischemic stroke and its impact on discharge and short term outcome.

PATIENTS AND METHODS

Consecutive patients who presented between 2-4 weeks post stroke were prospectively recruited. Study period was April 2012-March 2014 (2 years). Subjects underwent clinical autonomic function testing using Ewing's battery at bedside and 24h Holter analysis for heart rate variability(HRV). HRV parameters studied included both time domain and frequency domain measures. Neurological and cardiovascular outcomes were assessed at discharge,3 months and 1year.

RESULTS

Of 101 patients of mean age 63yrs, 72% were men.Majority had moderate to severe strokes at onset (Mean NIHSS-13.9,MRS-3.1). Clinical bedside autonomic testing criteria were comparable to Holter detected dysautonomia in our study population (p value 0.3). Clinical autonomic dysfunction had a positive association with male gender whereas onset stroke severity and Insular involvement were associated with significantly higher incidence of autonomic dysfunction with both methodology. Those with autonomic dysfunction had more stroke severity at discharge, which was independent of onset severity. Increasing age, hemispheric laterality or presence of comorbidities had no impact on post-stroke dysautonomia.

CONCLUSIONS

Insular involvement and higher disability at onset are associated with greater incidence of autonomic dysfunction post-stroke. Those with AD had higher chance of infarct expansion and in hospital cardiovascular complications and poorer outcome at 1year, independent of onset stroke severity.

Diabetic neuropathy: achieving best practice

Peripheral neuropathy is one of the commonest complications of diabetes and the commonest form of neuropathy in the developed world.1 Diabetic polyneuropathy encompasses several neuropathic syndromes, and the commonest presentation is chronic distal symmetrical neuropathy (DSP). DSP, often associated with autonomic neuropathy, has two clinical consequences: namely neuropathic pain and foot ulceration. Both often occur in the same individual, and cause severe curtailment of quality of life. The other, less common presentations of diabetic polyneuropathy include acute painful neuropathies, and focal neuropathies (amyotrophy, pressure palsies, truncal radiculopathies, mononeuropathies and mononeuritis multiplex).2 Table 1 shows a recent classification of diabetic polyneuropathy based upon the natural history of the various syndromes.3

Poor glycemic control impacts linear and non-linear dynamics of heart rate in DM type 2

INTRODUCTION: It is well known that type 2 diabetes mellitus (T2DM) produces cardiovascular autonomic neuropathy (CAN), which may affect the cardiac autonomic modulation. However, it is unclear whether the lack of glycemic control in T2DM without CAN could impact negatively on cardiac autonomic modulation. Objective: To evaluate the relationship between glycemic control and cardiac autonomic modulation in individuals with T2DM without CAN. Descriptive, prospective and cross sectional study.METHODS: Forty-nine patients with T2DM (51±7 years) were divided into two groups according to glycosylated hemoglobin (HbA1c): G1≤7% and G2>7.0%. Resting heart rate (HR) and RR interval (RRi) were obtained and calculated by linear (Mean iRR; Mean HR; rMSSD; STD RR; LF; HF; LF/HF, TINN and RR Tri,) and non-linear (SD1; SD2; DFα1; DFα2, Shannon entropy; ApEn; SampEn and CD) methods of heart rate variability (HRV). Insulin, HOMA-IR, fasting glucose and HbA1c were obtained by blood tests.RESULTS: G2 (HbA1c≤7%) showed lower values for the mean of iRR; STD RR; RR Tri, TINN, SD2, CD and higher mean HR when compared with G1 (HbA1c > 7%). Additionally, HbA1c correlated negatively with mean RRi (r=0.28, p=0.044); STD RR (r=0.33, p=0.017); RR Tri (r=-0.35, p=0.013), SD2 (r=-0.39, p=0.004) and positively with mean HR (r=0.28, p=0.045). Finally, fasting glucose correlated negatively with STD RR (r=-0.36, p=0.010); RR Tri (r=-0.36, p=0.010); TINN (r=-0.33, p=0.019) and SD2 (r=-0.42, p=0.002).CONCLUSION: We concluded that poor glycemic control is related to cardiac autonomic modulation indices in individuals with T2DM even if they do not present cardiovascular autonomic neuropathy.

Finger volume pulse waveforms facilitate reliable assessment of heart rate variability, but not blood pressure variability or baroreflex function

Background

We sought to determine whether heart rate variability (HRV), blood pressure (BP) variability, and baroreceptor-heart rate reflex sensitivity can be reliably assessed using finger volume pulse waveforms obtained from the commercially available EndoPAT device.

Methods

Non-invasive BP (Finometer Pro as a non-invasive standard) and finger volume (EndoPAT) waveforms were recorded in 65 adults (37 ± 14 years; 60% female) and systolic BP and heart rate (HR) time series were derived after calibrating the EndoPAT signal based on systolic and diastolic BP values obtained by a sphygomomanometer. Transfer function analyses were performed to test for coherence between systolic BP and HR time series derived from the Finometer and EndoPAT devices. Time-domain HRV parameters, frequency domain HR and systolic BP variability parameters, and baroreflex sensitivity (sequence technique) were computed from Finometer- and EndoPAT-derived time series and intraclass correlation coefficients (ICC) were calculated.

Results

Squared coherence between systolic BP time series derived from the Finometer and EndoPAT devices was low, suggesting poor correlation. In contrast, squared coherence between HR time series derived from the two devices was excellent [High Frequency (HF) = 0.80, Low Frequency (LF) = 0.81], with gain values close to 1.0. ICC values for time- and frequency-domain HRV parameters were excellent (>0.9 except for relative HF HRV, which was 0.77), while ICC values for frequency-domain BP variability parameters and baroreceptor-HR reflex sensitivity were low.

Conclusions

Finger volume pulse waveforms can be used to reliably assess both time-domain and frequency-domain HR variability. However, frequency domain BP variability parameters cannot be reliably assessed from finger volume pulse waveforms using the simple calibration technique used in this study.

Comparative study on cardiac autonomic modulation during deep breathing test and diaphragmatic breathing in type 2 diabetes and healthy subjects

AIMS/INTRODUCTION

Diaphragmatic breathing is known to have a beneficial effect on the cardiopulmonary system, and enhances parasympathetic activation. We evaluated the influence of diaphragmatic breathing on time domain measures of heart rate variability in diabetics and healthy subjects.

MATERIALS AND METHODS

A total of 122 type 2 diabetics and 94 healthy subjects (controls) were randomly allocated to a deep breathing test and diaphragmatic breathing (61 diabetics and 47 controls in each group). Heart rate variability parameters; namely, expiratory:inspiratory ratio (E:I ratio), root mean square of successive N-N interval difference (r-MSSD) and standard deviation of all the N-N intervals (SDNN), were quantified from 1-min supine electrocardiogram obtained while subjects carried out the deep breathing test/diaphragmatic breathing at six respiratory cycles per min. Data analysis was carried out by Student's unpaired t-test. A P-value <0.05 was taken as significant.

RESULTS

E:I ratio, SDNN and r-MSSD of type 2 diabetics was significantly lower compared with controls in the diaphragmatic group (P < 0.001). E:I ratio and SDNN were significantly lower in type 2 diabetics compared with controls in the deep breathing group (P < 0.0001, P < 0.019, respectively). In controls, E:I ratio, r-MSSD and SDNN of the diaphragmatic breathing group were significantly higher compared with the deep breathing group (P < 0.01). In diabetics, none of the measured heart rate variability parameters varied between diaphragmatic breathing and deep breathing.

CONCLUSIONS

Subclinical cardiac autonomic neuropathy persists in type 2 diabetics. In type 2 diabetics, diaphragmatic breathing quantifies certain aspects of parasympathetic dysfunction, which is not shown by the deep breathing test. Diaphragmatic breathing induces greater cardiac autonomic modulation in healthy subjects.

Cardiac autonomic dysfunction in type 2 diabetes - effect of hyperglycemia and disease duration

Heart rate variability (HRV) is reduced in diabetes mellitus (DM) patients, suggesting dysfunction of cardiac autonomic regulation and an increased risk for cardiac events. The aim of this paper was to examine the associations of blood glucose level (BGL), glycated hemoglobin (HbA1c), and duration of diabetes with cardiac autonomic regulation assessed by HRV analysis. Resting electrocardiogram (ECG), recorded over 20 min in supine position, and clinical measurements of 189 healthy controls and 93 type 2 DM (T2DM) patients were analyzed. HRV was assessed using several time-domain, frequency-domain, and non-linear methods. HRV parameters showed a clear difference between healthy controls and T2DM patients. Hyperglycemia was associated with increase in mean heart rate and decrease in HRV, indicated by negative correlations of BGL and HbA1c with mean RR interval and most of the HRV parameters. Duration of diabetes was strongly associated with decrease in HRV, the most significant decrease in HRV was found within the first 5-10 years of the disease. In conclusion, elevated blood glucose levels have an unfavorable effect on cardiac autonomic function and this effect is pronounced in long-term T2DM patients. The most significant decrease in HRV related to diabetes and thus presence of autonomic neuropathy was observed within the first 5-10 years of disease progression.

Testing the autonomic nervous system

Autonomic testing is used to define the role of the autonomic nervous system in diverse clinical and research settings. Because most of the autonomic nervous system is inaccessible to direct physiological testing, in the clinical setting the most widely used techniques entail the assessment of an end-organ response to a physiological provocation. The noninvasive measures of cardiovascular parasympathetic function involve the assessment of heart rate variability while the measures of cardiovascular sympathetic function assess the blood pressure response to physiological stimuli. Tilt-table testing, with or without pharmacological provocation, has become an important tool in the assessment of a predisposition to neurally mediated (vasovagal) syncope, the postural tachycardia syndrome, and orthostatic hypotension. Distal, postganglionic, sympathetic cholinergic (sudomotor) function may be evaluated by provoking axon reflex mediated sweating, e.g., the quantitative sudomotor axon reflex (QSART) or the quantitative direct and indirect axon reflex (QDIRT). The thermoregulatory sweat test provides a nonlocalizing measure of global pre- and postganglionic sudomotor function. Frequency domain analyses of heart rate and blood pressure variability, microneurography, and baroreflex assessment are currently research tools but may find a place in the clinical assessment of autonomic function in the future.

Autonomic dysfunction in ischemic stroke with carotid stenosis

OBJECTIVES

Impaired autonomic function is common in acute ischemic stroke. Previous limited studies have suggested that atherosclerosis may affect the distensibility of the carotid sinus and then impair the cardiovascular autonomic function. This study sought to investigate cardiovascular autonomic function in patients with ischemic stroke with carotid stenosis.

METHODS

Eighty-five patients with ischemic stroke (58 ones without carotid stenosis and 27 ones with carotid stenosis, average 6 months after stroke onset) and 37 elderly controls were recruited. All performed Ewing's battery autonomic function tests.

RESULTS

From Ewing's battery of autonomic function tests, atypical, definite, or severe autonomic dysfunction was identified in 69.0% patients without carotid stenosis and 88.9% with carotid stenosis, with significant difference between the two groups, and the prevalence of autonomic dysfunction in both groups was higher than that in controls (21.6%). Patients with carotid stenosis showed impairment of all parasympathetic tests (all P < 0.05) and one of the sympathetic tests [Mean fall in systolic blood pressure (BP) on standing: P = 0.051], and those without carotid stenosis only showed impairment in two parasympathetic tests (Valsalva ratio: P = 0.014; heart rate response to deep breathing: P < 0.001) in comparison with controls. Patients with carotid stenosis had significantly more impairment than those without carotid stenosis in some autonomic parameters (Valsalva ratio: P < 0.05; mean fall in systolic BP on standing: P < 0.05).

CONCLUSIONS

Cardiovascular autonomic function is impaired in patients with ischemic stroke, but patients with carotid stenosis show more severely impaired parasympathetic and sympathetic functions.

Comprehensive assessment for autonomic dysfunction in different phases after ischemic stroke

BACKGROUND AND PURPOSE

Studies mostly use the analysis of heart rate variability to measure cardiovascular autonomic regulation in ischemic stroke. Besides power spectral analysis of heart rate variability, this study sought to determine whether autonomic function was impaired during different phases in ischemic stroke by Ewing's battery of autonomic function tests.

METHODS

Ninety-four patients with ischemic stroke (34 patients in acute phase and 60 patients in chronic phase, average six-months after stroke onset) and thirty-seven elderly controls were recruited. Ewing's battery autonomic function tests and power spectral analysis of heart rate variability were performed in all the subjects.

RESULTS

From power spectral analysis of heart rate variability, stroke patients of both acute and chronic phases had significantly lower low frequency power spectral density than controls. From Ewing's battery of autonomic function tests, patients in acute phase showed impairment in two parasympathetic tests (Valsalva ratio: P = 0·002; heart rate response to deep breathing: P < 0·001) and those in chronic phase showed impairment in all parasympathetic tests (all P < 0·05) in comparison with controls.

CONCLUSIONS

The comprehensive assessment indicates that autonomic dysfunction occurs in acute phase of ischemic stroke and may persist up to six-months after stroke. Parasympathetic dysfunction rather than sympathetic dysfunction is predominant after ischemic stroke.

Autonomic function following acute organophosphorus poisoning: a cohort study

Autonomic dysfunction after chronic low level exposure to organophosphorus (OP) pesticides has been consistently reported in the literature, but not following a single acute overdose. In order to study autonomic function after an acute OP overdose, sixty-six overdose patients were compared to 70 matched controls. Assessment of autonomic function was done by heart rate response to standing, deep breathing (HR-DB) and Valsalva manoeuvre; blood pressure (BP) response to standing and sustained hand grip; amplitude and latency of sympathetic skin response (SSR); pupil size and post-void urine volume. The patients were assessed one and six weeks after the exposure. The number of patients who showed abnormal autonomic function compared to standard cut-off values did not show statistically significantly difference from that of controls by Chi-Square test. When compared to the controls at one week the only significant differences consistent with autonomic dysfunction were change of diastolic BP 3 min after standing, HR-DB, SSR-Amplitude, SSR-Latency, post-void urine volume and size of the pupil. At 6 weeks significant recovery of autonomic function was observed and only HR-DB was decreased to a minor degree, −5 beats/min [95%CI 2–8]. This study provides good evidence for the lack of long term autonomic dysfunction following acute exposure to OP pesticides.

Preliminary findings of the effects of autonomic dysfunction on functional outcome after acute ischemic stroke

BACKGROUND AND PURPOSE

Impaired autonomic function is common in the acute poststroke phase but little is known about its effects on functional outcome after acute ischemic stroke. This study sought to investigate the impact of autonomic dysfunction by Ewing's classification on functional outcome 2 months after acute ischemic stroke.

METHODS

34 consecutive acute ischemic stroke patients within 7 days after onset were enrolled. On admission, autonomic function was assessed by Ewing's battery tests. Stroke severity was assessed by the National Institutes of Health Stroke Scale (NIHSS), autonomy in activities of daily living by the Barthel Index (BI), and global disability by the modified Rankin Scale (mRS). BI and mRS were also evaluated 2 months after ischemic stroke onset.

RESULTS

On admission, eight patients were diagnosed as minor autonomic dysfunction and 26 patients as relatively severe autonomic dysfunction. The prevalence of relatively severe autonomic dysfunction in ischemic stroke patients was 76.5%. There were no significant differences in baseline characteristics between the minor and severe autonomic dysfunction groups. 2 months after stroke onset, the mean BI score of patients with minor autonomic dysfunction and severe autonomic dysfunction increased from 76.3±15.3 on admission to 95.0±7.1, 66.5±15.2 on admission to 74.8±15.9 respectively. The mean BI score after 2-month stroke onset and the change in BI from admission to 2-month outcome (delta BI) in patients with severe autonomic dysfunction were lower than those in patients with minor autonomic dysfunction (all P<0.05).

CONCLUSIONS

Autonomic dysfunction occurs in acute stroke patients. Relatively severe autonomic dysfunction is related to an unfavorable functional outcome in patients with acute ischemic stroke.

Autonomic cardiovascular tests in children with obstructive sleep apnea syndrome

STUDY OBJECTIVES

The aim of our study was to investigate cardiovascular autonomic activity during wakefulness, using cardiovascular tests, in a population of children with OSAS.

DESIGN

Prospective study.

SETTING

Sleep unit of an academic center.

PARTICIPANTS

We included 25 children (mean age 10.2 +/- 2.3 years) undergoing a diagnostic assessment for OSAS, and 25 age-matched healthy control subjects. All subjects underwent an overnight polysomnography and autonomic cardiovascular tests using parts of the Ewing test battery, which is a physiological test used for the assessment of autonomic function (head-up tilt test, Valsalva maneuver, deep breathing test).

MEASUREMENTS AND RESULTS

Eighteen of 25 children with OSAS (11 males, mean age 9.4 +/- 1.7 years) concluded the study. OSAS patients had higher systolic blood pressure, diastolic blood pressure, baseline heart rate, the 30:15 index (which represents the RR interval at the 15th and 30th beats during the head up tilt test), and delta diastolic and systolic blood pressure during the head-up tilt test, while the heart rate variability during the deep breathing test was lower, compared with controls. A positive correlation between systolic and diastolic blood pressure and the apnea-hypopnea index (AHI), and negative between AHI and both the 30:15 index and Valsalva ratio, were found. Stepwise linear regression analysis detected a negative correlation between AHI and the 30:15 index and Valsalva ratio, a positive correlation between overnight mean oxygen saturation and delta heart rate, and between AHI and delta systolic blood pressure.

CONCLUSIONS

Our data point to an increase in basal sympathetic activity during wakefulness and to an impaired reaction to several physiological stimuli, which is dependent on the severity of OSAS.

[Cardiovascular impact of the autonomic neuropathy of diabetes mellitus]

The neuropathic complications related to Diabetes may affect the somatic, sympathetic and parasympathetic nervous system. As a result, there are several clinical manifestations of diabetic neuropathy. They can be related to nervous system lesions of the genital, urinary, gastro-intestinal, skin and cardiovascular tissues. The results of these alterations are loss in the quality of life as well as increase of mortality indexes related to sudden death with cardiac arrhythmias and other causes. The cardiovascular autonomic neuropathy probably contributes to the bad prognosis of the coronary heart disease and of the heart failure in type 1 and type 2 diabetic patients. For diabetologists, the nervous complications of diabetes are the result of an increase influx of glucose to the neuronal and endothelial cells. Evidences show that, with the aim of preventing these complications, the diabetic patients should receive a precocious diagnosis and be instructed for having a good metabolic and blood pressure control. Use of angiotensin converting enzyme inhibitors and beta adrenergic blockers are probably of impact in the prevention of the cardiac autonomic complications of diabetes.

Sex differences in cardiac vagal control in a depressed sample: implications for differential cardiovascular mortality

Previous studies suggest depression is a risk factor for all cause mortality, with depressed men at greater risk than depressed women. Diminished cardiac vagal control (CVC) in depressed patients has also been found to increase risk of cardiac mortality. Previous research found that depressed women have higher CVC than depressed men suggesting CVC might be related to the discrepancy in mortality rates between depressed men and women. This finding, however, was in the context of a study with several methodological weaknesses. The current study sought to replicate the sex difference in CVC in a sample of 137 medically healthy and clinically diagnosed depressed patients. Main effects of sex and age significantly predicted CVC such that depressed women had greater CVC and CVC decreased with age in the cross-sectional sample. The results suggest greater CVC in depressed women might confer cardioprotective functions, which may partially explain the sex difference in mortality rates in the depressed population.

Autonomic dysfunction in obstructive sleep apnea is associated with impaired glucose regulation

INTRODUCTION

Autonomic dysfunction has been theorized to be responsible for the increased risk of cardiovascular disease in obstructive sleep apnea (OSA). Previous studies did not control for the presence of impaired glucose regulation (IGR, comprising impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes) which is also associated with abnormalities in autonomic function.

METHODS

Thirty-two patients were recruited for the study. Patients underwent autonomic testing consisting of heart rate response to deep breathing, valsalva maneuver, tilt-up, and quantitative sudomotor axon reflex testing. Polysomnography (PSG) and a 2-h oral glucose tolerance test were performed. Results were analyzed with logistic regression, with age, race, body mass index (BMI), and gender as covariates.

RESULTS

Nineteen of 24 patients with OSA had abnormal glucose (79%, p=0.04) compared to two of nine patients without OSA. The correlation between IGR, OSA and total autonomic dysfunction was similar (p=.10 for IGR, p=0.06 for OSA). However, cardiac autonomic function was more strongly associated with IGR than OSA (p=.10 vs. 0.50). Age was a significant confounder, as glucose correlated with adrenergic autonomic dysfunction significantly when age was removed from the model (p=0.006).

CONCLUSIONS

The presence of IGR may be a confounding factor in studies of autonomic function in OSA. Larger studies are needed to delineate whether OSA is directly associated with autonomic dysfunction or whether the previously described association between dysautonomia and OSA may have been due to glucose dysregulation.

Diabetes mellitus and cardiovascular disease

Cardiovascular diseases include hypertension, coronary heart disease, acute myocardial infarction, heart failure, sudden death, peripheral vascular disease, and stroke. The high risk of cardiovascular disease in individuals with diabetes was recognized more than 30 years ago. Appreciation of the multiple risk factors and complex pathophysiologic process responsible for cardiovascular disease in individuals with both type 1 and 2 diabetes is critical for the prevention, early detection, and management of cardiovascular disease in this population. The focus of this article is on the acute and chronic manifestations of coronary heart disease.

The many metrics of cardiac chronotropy: a pragmatic primer and a brief comparison of metrics

This paper focuses on pragmatic issues in obtaining measures of cardiac vagal control, and overviews a set of freely available software tools for obtaining several widely used metrics that putatively reflect sympathetic and/or parasympathetic contributions to cardiac chronotropy. After an overview of those metrics, and a discussion of potential confounds and extraneous influences, an empirical examination of the relationships amongst these metrics is provided. This study examined 10 metrics in 96 unselected college students under conditions of resting baseline and serial paced arithmetic. Intercorrelations between metrics were very high. Factor analyses were conducted on the metrics reflecting variability in cardiac rate, once at baseline and again during mental arithmetic. Factor structure was highly stable across tasks, and included a factor that had high loadings of all variables except Toichi's "cardiac sympathetic index" (CSI), and a second factor that was defined predominantly by the CSI. Although generally highly correlated, the various metrics responded differently under challenge.

Aberrant parasympathetic and hemodynamic function distinguishes a subgroup of psychologically distressed individuals with asymptomatic type-I diabetes mellitus

In a previous study, a subgroup of asymptomatic insulin-dependent diabetic individuals (termed IDDM-2) were identified on the basis of diminished parasympathetic cardiac input and elevated heart rate at rest. When compared to another group of asymptomatic IDDM participants (termed IDDM-1), and a nondiabetic healthy control group, the IDDM-2 group displayed elevated blood pressure, supported by elevated total peripheral resistance. Measures of psychological regulation were also taken in this study, and form the basis of this article, which examined whether these IDDM-2 patients differed from the other two groups on these measures. The possible role of glycemic control, IDDM duration, and number of somatic complaints among group differences in psychological regulation was also examined. The IDDM-2 group reported increased psychological distress, as reflected by increased dysphoric or depressive symptoms, trait anxiety, perceived stress, and cynical hostility, as well as decreased optimism and interpersonal, but not family, social support. Glycemic control did not account for any of the group differences in psychological regulation. However, group differences in dysphoria and anxiety were accounted for by differences in somatic complaints, whereas differences in interpersonal social support were accounted for by IDDM duration. Moreover, none of the variables investigated accounted for the diminished optimism of the IDDM-2 group. Therefore, in individuals with IDDM, who would otherwise be considered, after medical examination, as no different from other asymptomatic IDDM individuals, the combination of diminished parasympathetic cardiac input and elevated heart rate was associated with aberrant alterations of both hemodynamic and psychological functioning; the increased psychological distress in these individuals may be influenced, in part, by increased diabetes duration and number of somatic symptoms.

Right-left correlation of the sympathetically induced fluctuations of photoplethysmographic signal in diabetic and non-diabetic subjects

Photoplethysmography (PPG) records the cardiac-induced changes in tissue blood volume by light-transmission measurements. The baseline and amplitude of the PPG signal show very low-frequency (VLF) spontaneous fluctuations, which are mediated by the sympathetic nervous system, and high correlation between right and left extremities of healthy subjects. As sympathetic neuropathy is one of the diabetic complications, the right-left correlation of the PPG fluctuations was examined in diabetic patients. The PPG signal was simultaneously measured in the two index fingers and the two second toes of 35 diabetic patients and 33 non-diabetic subjects. For each PPG pulse, the baseline and amplitude were determined, and the right-left correlation coefficients of the VLF fluctuations in the baseline and amplitude were derived. The VLF fluctuations in the baseline showed high right-left correlation, both for fingers (0.93 +/- 0.05) and toes (0.93 +/- 0.06), for the non-diabetic subjects, and significantly lower correlation (0.78 +/- 0.22 and 0.84 +/- 0.17, respectively) for the diabetic patients. Similar results were obtained for the amplitude VLF fluctuations. The right-left correlation coefficients for diabetic patients decreased with the disease duration for the toe baseline and toe amplitude fluctuations and correlated with heart rate response to deep breathing for the finger baseline and toe amplitude fluctuations. The right-left correlation coefficients of the PPG fluctuations provide a simple and convenient means for assessing the adequacy of the sympathetic nervous system function.

Diabetic Neuropathies

Diabetes mellitus is associated with a wide spectrum of neuropathy syndromes, ranging from a mild asymptomatic distal sensory neuropathy to a severe disabling radiculoplexus neuropathy. As the pathophysiology of these separate conditions is better understood, classification of the various phenotypes becomes important because of treatment implications. Here we provide a short summary of the history of the classification of diabetic neuropathies and try to describe the most common forms classified according to their presumed pathophysiology. We have tried to include epidemiological data where available, as well as histopathology of nerve in several diabetic neuropathies.

Erectile dysfunction as a sentinel symptom of cardiovascular autonomic neuropathy in heavy drinkers

Because autonomic neuropathy (AN) is not routinely assessed in chronic alcoholism, its features and relationship with other disease parameters remain undefined. The very existence of true alcohol-related autonomic dysfunction, in the absence of alcoholic hepatopathy, is even controversial. We aimed this study at evaluating the frequency and pattern of AN in a population of heavy drinkers without liver dysfunction. We also investigated the putative risk factors for AN as well as its relationship to peripheral neuropathy (PN). Autonomic function was evaluated in 70 detoxified alcoholics and 70 well-matched controls by heart-rate response to deep breathing, heart-rate response to standing from lying position, and blood pressure response to standing up. PN was assessed by electroneurography (ENG). Detailed information about sensorimotor and autonomic symptoms, nutritional status, and parameters reflecting alcohol intake were recorded. No patients showed signs of caloric/protein malnutrition. PN was found in 74% and AN (abnormal test results in two of three tests performed) in 26%; abnormalities in at least one autonomic test were found in 62%. All patients with PN were symptomatic, mainly due to sensory disturbances. In line with this, ENG abnormalities were more evident at sural nerves. AN was symptomatic in 10 of 18 patients, and its sole clinical expression was impotence: indeed, the pattern of autonomic involvement was mainly parasympathetic. AN did not correlate with PN, nor with any parameter reflecting the amount of alcohol intake; only performances on heart-rate response to standing from lying position were related to the duration of abuse. The lack of correlation between PN and AN may suggest a different pathophysiology for these two complications. Unlike PN, AN is often asymptomatic. Among symptomatic patients (55%), erectile dysfunction seems to be the sole symptom, in line with the higher degree of parasympathetic damage.

Differential index, a novel graphical method for measurements of heart rate variability

BACKGROUND

Commonly used methods to evaluate heart rate variability require extensive filtering of the registrations in order to exclude artefacts and ectopic beats. We developed and validated a novel graphical method for time-domain measurements of heart rate variability, the differential index, which does not require filtering and is simple to use.

METHODS

The 24-h ambulatory long-term electrocardiogram recordings from 120 patients with angina pectoris and 49 control subjects were computerised without any filtering process. Sample density histograms of differences in the RR interval for successive beats were constructed and the widths of the histograms were used to obtain the differential index. For comparison, the same registrations were analysed by conventional methods.

RESULTS

The differential index was most closely related (P<0.001) to conventional short-term time domain (e.g. percent of differences between adjacent normal RR intervals >50 ms, pNN50, r=0.81) and frequency-domain (e.g. high frequency power, r=0.84) components, but also to long-term time domain (e.g. standard deviation of all normal-to-normal RR intervals for all 5-min segments of the entire registration, SDNNIDX, r=0.72) and frequency-domain (e.g. low frequency power, r=0.64) components.

CONCLUSION

The differential index method shows good agreement with established indices of heart rate variability. The insensitivity to recording artefacts and short-lasting disturbances of sinus rhythm make the differential index method particularly suited when data quality is imperfect. The simplicity of the method is valuable when large numbers of registrations are to be evaluated.

QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ankle brachial pressure index and autonomic function tests

OBJECTIVES

To study serial measures of maximum QT interval corrected for heart rate (QTc) and QT dispersion (QTD) and their association with cardiac mortality patients with non-insulin dependent diabetes and to compare QT abnormalities with other mortality predictors (ankle brachial pressure index (ABPI) and autonomic function tests) in their ability to predict cardiac death.

SETTING

Teaching hospital.

METHODS AND PATIENTS

QT interval analysis, heart rate (RR) variation in response to deep breathing and standing, and ABPI were analysed in 192 patients with non-insulin dependent diabetes. Cardiac death was the primary end point.

RESULTS

Mean (SD) follow up was 12.7 (3.2) years (range 1.2-17.1 years). There were 48 deaths, of which 26 were cardiac. QTc and QTD were individually significant predictors of cardiac mortality throughout the follow up period (p < 0.001). The predictability of QT parameters was superior to the predictability of ABPI and RR interval analysis. Temporal changes in QT parameters showed that the mean absolute QT parameter was a significant predictor of cardiac death (p < 0.001), whereas an intraindividual change in QT parameter over time was not predictive.

CONCLUSION

QT abnormalities seem to exist at the point of diagnosis of diabetes and do not appear to change between then and the subsequent cardiac death. Furthermore, the analysis of QT interval is superior to ABPI and the RR interval in identifying diabetic patients at high risk of cardiac death.

Effectiveness of Semmes-Weinstein monofilament examination for diabetic peripheral neuropathy screening

OBJECTIVE

To evaluate the effectiveness of the Semmes-Weinstein monofilament examination (SWME) for diabetic peripheral neuropathy (DPN) screening at an outpatient clinic.

METHODS

Eighty-two type 2 diabetic outpatients were questioned about 13 subjective symptoms and tested for deep reflexes. They were examined using two types of quantitative sensory testing: SWME (using 4.31/2 g and 5.07/10 g monofilaments) and vibration testing (using the C-64 quantitative tuning fork). The patients were diagnosed with DPN when two of the following three criteria from both legs were met: (1) the presence of either pain, numbness, or paraesthesia; (2) a diminished or absent ankle reflex; or (3) a scale below 4 for their vibration perception thresholds (VPT).

RESULTS

The most common subjective symptoms were muscle cramps and numbness in the extremities. SWME 4.31/2 g at the great toe or the plantar aspect of the fifth metatarsal was the most useful diagnostic test for DPN, providing 60.0% sensitivity and 73.8% specificity. SWME 4.31/2 g was correlated with lower limb VPT (P=.029) and three subjective symptoms including fainting. SWME 5.07/10 g was correlated with lower limb VPT (P=.011), the ankle reflex (P=.013), the knee reflex (P=.031), and two subjective symptoms. However, the sensitivity to diagnose DPN was low (30.0%).

CONCLUSIONS

The abnormalities indicated by SWME correlated well with those identified by lower limb VPT. Moreover, SWME 4.31/2 g correlated with fainting, suggesting that it could detect abnormalities in the small fibers. Considering the minimal time for this examination, SWME 4.31/2 g is a useful examination in an outpatient setting along with lower limb VPT and ankle reflex testing.

Detection of silent myocardial ischemia in asymptomatic diabetic subjects: the DIAD study

OBJECTIVE

To assess the prevalence and clinical predictors of silent myocardial ischemia in asymptomatic patients with type 2 diabetes and to test the effectiveness of current American Diabetes Association screening guidelines.

RESEARCH DESIGN AND METHODS

In the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study, 1,123 patients with type 2 diabetes, aged 50-75 years, with no known or suspected coronary artery disease, were randomly assigned to either stress testing and 5-year clinical follow-up or to follow-up only. The prevalence of ischemia in 522 patients randomized to stress testing was assessed by adenosine technetium-99m sestamibi single-photon emission-computed tomography myocardial perfusion imaging.

RESULTS

A total of 113 patients (22%) had silent ischemia, including 83 with regional myocardial perfusion abnormalities and 30 with normal perfusion but other abnormalities (i.e., adenosine-induced ST-segment depression, ventricular dilation, or rest ventricular dysfunction). Moderate or large perfusion defects were present in 33 patients. The strongest predictors for abnormal tests were abnormal Valsalva (odds ratio [OR] 5.6), male sex (2.5), and diabetes duration (5.2). Other traditional cardiac risk factors or inflammatory and prothrombotic markers were not predictive. Ischemic adenosine-induced ST-segment depression with normal perfusion (n = 21) was associated with women (OR 3.4). Selecting only patients who met American Diabetes Association guidelines would have failed to identify 41% of patients with silent ischemia.

CONCLUSIONS

Silent myocardial ischemia occurs in greater than one in five asymptomatic patients with type 2 diabetes. Traditional and emerging cardiac risk factors were not associated with abnormal stress tests, although cardiac autonomic dysfunction was a strong predictor of ischemia.

Influence of sleep apnea on autonomic nervous activity and QT dispersion in patients with essential hypertension and old myocardial infarction

Sleep apnea syndrome (SAS) is an important cardiovascular risk factor in patients with hypertension or myocardial infarction (MI). We evaluated the influence of SAS on autonomic nervous activity and QT dispersion in patients with hypertension or coronary artery disease with old MI. A portable sleep polygraph was attached to 30 healthy volunteers (N group), 30 patients with essential hypertension (HT group), and 30 patients with old myocardial infarction (MI group) to serially record oronasal respiration, tracheal sound, thoracic respiratory movement, and percutaneous arterial oxygen saturation. In addition, a digital Holter ECG was used to examine heart rate variability during nighttime sleep. Heart rate variability was analyzed by obtaining low-frequency (LF) power, high-frequency (HF) power, the LF/HF ratio, and very low-frequency (VLF) power. Dispersion of QT intervals was obtained by CM5 and CM1 leads. VLF and LF powers were significantly higher in the HT-SAS group (hypertensive patients with SAS) than the N and HT-NSAS groups (hypertensive patients without SAS). The HF power was significantly lower in the HT-NSAS group than the N group, but the decrease in HF power in hypertension was not observed in the HT-SAS group. The LF/HF ratio was significantly higher in the HT-NSAS group than the N group, and this value was further increased in the HT-NSAS group. Percutaneous arterial oxygen saturation was decreased, and QT dispersion was significantly increased in the MI group during sleep apnea episodes. More severe autonomic nervous dysfunction and increased QTc dispersion were observed in hypertensive patients with SAS during episodes of apneas and hypopneas compared to those without SAS. These findings suggest that SAS may be associated with the future development of cardiac events.