Power spectral analysis of heart rate variation in diabetic patients with neuropathic foot ulceration

Cardiac electrophysiology, structure and diastolic function in patients with diabetic foot versus those without diabetic foot

AIMS/INTRODUCTION

To evaluate the differences in cardiac autonomic function, cardiac structure and diastolic function between individuals with diabetic foot (DF) and those with diabetes but without DF.

MATERIALS AND METHODS

A total of 413 individuals with DF and 437 without DF who underwent a 24-h electrocardiogram Holter and a Doppler echocardiogram were included. The heart rate variability parameters to evaluate cardiac autonomic function, and the indices for the assessment of cardiac structure and left ventricular (LV) diastolic function, including left atrium, LV posterior wall thickness, interventricular septum and E/e' ratio, were measured or calculated. Propensity score matching was used for the sensitivity analysis to minimize potential imbalance.

RESULTS

In both the crude and propensity score matching analyses, significant differences were observed in heart rate variability between individuals with and without DF, as evidenced by lower standard deviation of the normal sinus interval, lower low-frequency power/high-frequency power ratio, lower standard deviation of the 5-min average RR intervals, lower low-frequency power, lower percentage of normal adjacent RR interval difference >50 ms, lower root mean square of successive RR interval differences and lower high-frequency power (all P < 0.05). In multivariate analysis, DF showed an independent negative correlation with the aforementioned indices of heart rate variability (all P < 0.05). Individuals with DF showed higher left atrium, LV posterior wall thickness, interventricular septum and a higher E/e' ratio than those without DF in the crude analysis (all P < 0.05), whereas these indices were no longer associated with DF in the multivariate analysis and the propensity score matching analyses.

CONCLUSIONS

Cardiac autonomic modulation was more severely impaired in individuals with DF than in their counterparts without DF. There has been insufficient evidence to demonstrate the independent association of DF and LV diastolic dysfunction.

Association between corrected QT interval and long-term cardiovascular outcomes in elderly patients who had undergone endovascular therapy for lower extremity arterial disease

Background

Population-based studies have reported the association between prolonged corrected QT (QTc) intervals and an increased risk of adverse cardiovascular events. Data regarding the association between longer QTc intervals and incident cardiovascular outcomes in patients with lower extremity arterial disease (LEAD) are scarce.

Objective

To examine the impact of QTc interval on long-term cardiovascular outcomes in elderly patients with symptomatic LEAD.

Methods

This cohort study extracted data from the Tzu-chi Registry of ENDovascular Intervention for Peripheral Artery Disease (TRENDPAD) and enrolled 504 patients aged ≥ 70 treated with endovascular therapy for atherosclerotic LEAD from July 1, 2005, to December 31, 2019. The main outcomes of interest were all-cause mortality and major adverse cardiovascular events (MACE). Multivariate analysis was conducted using the Cox proportional hazard model to determine independent variables. We performed interaction analysis between corrected QT and other covariates and Kaplan-Meier analysis to compare the outcome of interest among the groups stratified by the tercile of QTc intervals.

Results

A total of 504 patients [235 men (46.6%); mean age, 79.9 ± 6.2 years; mean QTc interval, 459 ± 33 msec] entered the final data analysis. We categorized the baseline patient characteristics according to terciles of QTc intervals. During the median follow-up time of 3.15 (interquartile ranges, 1.65-5.42) years, we noted 264 deaths and 145 MACEs. The 5-year rates of freedom from all-cause mortality (71% vs. 57% vs. 31%, P < 0.001) and MACEs (83% vs. 67% vs. 46%, P < 0.001) were significantly different among the tercile groups. Multivariate analysis showed that a 1-SD increase in the QTc interval increased the risk of all-cause mortality [hazard ratio (HR) 1.49, P < 0.001] and MACEs (HR 1.59, P < 0.001) after adjusting for other covariates. The interaction analysis showed that QTc interval and C-reactive protein levels were most strongly associated with death (HR = 4.88, 95% CI 3.09-7.73, interaction P < 0.001) and MACEs (HR = 7.83, 95% CI 4.14-14.79, interaction P < 0.001).

Conclusions

In elderly patients with symptomatic atherosclerotic LEAD, a prolonged QTc interval is associated with advanced limb ischemia, multiple medical comorbidities, increased risk of MACEs, and all-cause mortality.

Correlation between Palpitations below the Heart in Traditional Chinese Medicine and Autonomic Nerve Function Based on Heart Rate Variability: A Case-Control Study

Objective

To explore the autonomic nerve rhythm and the correlation between palpitations below the heart (PBTH) and autonomic nerve function in patients with PBTH based on heart rate variability (HRV).

Methods

The outpatients or ward patients of Wenzhou Hospital of Traditional Chinese Medicine were collected and divided into two groups: the PBTH group and the normal group. The HRV of each group was detected. Single-factor statistical methods, Spearman correlation analysis, and logistic regression were used to describe and analyze the rhythm and characteristics of autonomic nerves in patients with PBTH and the correlation between PBTH and autonomic nerve function.

Results

(1) In the comparison of HRV in different time periods in the same group, the SDNN, RMSSD, pNN50, TP, and HF in the PBTH group at night were significantly higher than those in the daytime (P < 0.01), while the LF/HF ratio was significantly lower than that in the daytime (P < 0.01). (2) In the comparison of HRV between the two groups in the same time period, the RMSSD and pNN50 of the PBTH group during the daytime period were significantly higher than those of the normal control group (P < 0.05), and the LF/HF was significantly lower than that of the normal group (P < 0.05). (3) In the Spearman correlation analysis, PBTH was significantly correlated with RMSSD, pNN50, and LF/HF ratio in the daytime period, with correlation coefficients of 0.424, 0.462, and -0.524, respectively (P < 0.05). (4) Logistic regression analysis showed that the decrease of LF/HF ratio during the daytime period was an independent risk factor for PBTH in TCM (OR = 0.474, 95% CI: 0.230-0.977, P < 0.05).

Conclusions

The changes in parasympathetic nerve function in patients with PBTH have a circadian rhythm, which is characterized by increased activity during the nighttime. At the same time, the autonomic nerve activity of people with PBTH during the daytime is unbalanced, and the decrease of LF/HF ratio during the day is an independent high risk factor for PBTH.

Assessment of heart rate variability (HRV) in subjects with type 2 diabetes mellitus with and without diabetic foot: correlations with endothelial dysfunction indices and markers of adipo-inflammatory dysfunction

Background

Some studies have suggested that patients with diabetes and foot complications have worse cardiovascular and cerebrovascular risk profiles, higher degrees of endothelial dysfunction and arterial stiffness and a higher inflammatory background than patients with diabetes without diabetic foot complications. Patients with diabetes mellitus have an alteration in the sympathovagal balance as assessed by means of heart rate variability (HRV) analysis, which is also related to the presence of endothelial dysfunction. Other studies suggest a possible role of inflammation coexisting with the alteration in the sympathovagal balance in favor of the atherosclerotic process in a mixed population of healthy subjects of middle and advanced age.

Aims

The aim of this study was to evaluate the degree of alteration of sympathovagal balance, assessed by HRV analysis, in a cohort of patients with diabetes mellitus with diabetic foot and in control subjects without diabetic foot compared with a population of healthy subjects and the possible correlation of HRV parameters with inflammatory markers and endothelial dysfunction indices.

Methods

We enrolled all patients with diabetic ulcerative lesions of the lower limb in the Internal Medicine with Stroke Care ward and of the diabetic foot outpatient clinic of P. Giaccone University Hospital of Palermo between September 2019 and July 2020. 4-h ECG Holter was performed. The following time domain HRV measures were analyzed: average heart rate, square root of the mean of successive differences of NN (RMSSD), standard deviation or square root of the variance (SD), and standard deviation of the means of the NN intervals calculated over a five-minute period (SDANN/5 min). The LF/HF ratio was calculated, reactive hyperemia was evaluated by endo-PAT, and serum levels of vaspine and omentin-1 were assessed by blood sample collection.

Results

63 patients with diabetic foot, 30 patients with diabetes and without ulcerative complications and 30 patients without diabetes were enrolled. Patients with diabetic ulcers showed lower mean diastolic blood pressure values than healthy controls, lower MMSE scores corrected for age, lower serum levels of omentin-1, lower RHI values, higher body weight values and comparable body height values, HF% and LF/HF ratio values. We also reported a negative correlation between the RHI value and HRV indices and the expression of increased parasympathetic activity (RMSDD and HF%) in subjects with diabetic foot and a statistically significant positive correlation with the LF/HF ratio and the expression of the sympathovagal balance.

Discussion

Patients with diabetic foot show a higher degree of activation of the parasympathetic system, expressed by the increase in HF values, and a lower LF/HF ratio. Our findings may corroborate the issue that a parasympathetic dysfunction may have a possible additive role in the pathogenesis of other vascular complications in subjects with diabetic foot.

Association between QTc interval prolongation and outcomes of diabetic foot ulcers: Data from a 4-year follow-up study in China

OBJECTIVES

To examine whether QTc interval prolongation is an independent risk factor of outcomes in patients with diabetic foot ulcers (DFU).

RESEARCH DESIGN AND METHODS

331 patients with type 2 diabetes and DFU hospitalized in a Chinese tertiary hospital were recruited. ECG was done at baseline and QTc interval was calculated through Bazett's formula. Participants were classified into 2 groups according to the QTc interval as prolonged (≥440 ms) or not (<440 ms). These patients were followed-up for an average of 48 months to observe the outcomes, including ulcer healing, ulcer recurrence, nonfatal cerebral or cardiovascular events (NCCVE), cerebral cardiovascular death, cardiac death and all-cause death. The associations between the risk of outcomes and QTc interval prolongation, as well as per 1-SD increase in QTc interval were analyzed by Cox proportional-hazards models.

RESULTS

In terms of the univariate Cox proportional hazard models, patients with QTc interval prolongation had a higher all-cause mortality (HR = 1.621, 95%CI: 1.040-2.526, P = .013), higher cardiac mortality (HR = 2.011 95%CI: 1.106-3.657, P = .019), higher cerebral cardiovascular mortality (HR = 1.525, 95%CI: 0.8151-2.852, P = .045). The multivariate analysis showed that QTc prolongation was an independent risk factor for cardiac death (HR = 5.465, 95%CI: 2.818-8.112, P = .039). Similar results were obtained when QTc interval was used as a continue variable, a 1-SD increase in QTc interval was associated with an 5.883 times risk for cardiac mortality (HR = 6.883, 95%CI: 4.153-9.613, P = .012). The association between QTc interval prolongation with ulcer healing, recurrence and NCCVE were not observed either in univariate or multivariate analysis (P > .05).

CONCLUSION

QTc interval prolongation was a plausible predictor for cardiac death in DFU patients, but it cannot accurately predict ulcer healing or recurrence.

Hyperuricemia is associated with decreased changes in heart rate variability after hemodialysis in non-diabetic patients

Hyperuricemia has been associated with low heart rate variability (HRV), however whether there is an association between uric acid (UA) and HRV changes after hemodialysis (HD) is unknown. The aim of this study was to investigate the role of UA in HRV changes before and after HD in non-diabetic patients. Ninety-six non-diabetic patients under maintenance HD were enrolled. HRV was examined to assess changes before and after HD. A change in HRV (ΔHRV) was calculated as post-HD HRV minus pre-HD HRV. Compared to the patients with a UA level ≦ 7 mg/dL, those with a UA level > 7 mg/dL had lower ∆high frequency (HF)% (p = 0.027). UA was negatively associated with ∆HF% (r = -0.247, p = 0.015) and ∆low frequency (LF)/HF (r = -0.236, p = 0.021) in the non-diabetic patients undergoing HD. Furthermore, in multivariate analysis after adjustments for demographic, clinical, and biochemical characteristics and medications, UA was independently associated with ∆HF% (per 1 mg/dL, unstandardized coefficient β = -2.892; 95% CI, -5.066 to -0.717; p = 0.010) and ∆LF/HF (per 1 mg/dL, unstandardized coefficient β = -0.165; 95% CI, -0.291 to -0.038; p = 0.011). Hyperuricemia contributed to lesser HF% and LF/HF increase after HD in the non-diabetic patients, reflecting a state of impaired sympatho-vagal equilibrium in non-diabetic HD patients with hyperuricemia. Lowering UA levels may have the potential to improve increased HRV in non-diabetic HD patients.

Cardiovascular Autonomic Dysfunction Predicts Diabetic Foot Ulcers in Patients With Type 2 Diabetes Without Diabetic Polyneuropathy

We investigated the factors that might influence the development of diabetic foot ulcers (DFUs) in type 2 diabetes patients without diabetic polyneuropathy (DPN).From January 2000 to December 2005, a total of 595 patients who had type 2 diabetes without DPN between the ages of 25 and 75 years, and had no prior history of DFUs were consecutively enrolled in the study. A cardiovascular autonomic function test was performed to diagnose cardiovascular autonomic neuropathy (CAN) using heart rate variability parameters.The median follow-up time was 13.3 years. Among the 449 (75.4%) patients who completed the follow-up evaluation, 22 (4.9%) patients developed new ulcers, and 6 (1.3%) patients underwent the procedure for lower extremity amputations. The patients in the DFUs group had a longer duration of diabetes, higher baseline HbA1c levels, higher rates of nephropathy, and CAN. A Cox hazard regression analysis results revealed that the development of DFUs was significantly associated with the presence of CAN (normal vs definite CAN; HR, 4.45; 95% confidence interval, 1.29-15.33) after adjusting for possible confounding factors.The development of DFUs was independently associated with CAN in patients with type 2 diabetes without DPN. We suggested the importance of CAN as a predictor of DFUs even in the patients without DPN, and the need to pay attention to patients with definite CAN and type 2 diabetes.

Link between Peripheral Artery Disease and Heart Rate Variability in Hemodialysis Patients

Peripheral artery disease (PAD) and low heart rate variability (HRV) are highly prevalent in hemodialysis patients, and both are associated with increased cardiovascular morbidity and mortality. This study aims to examine the suggested relationship between PAD and HRV, and the relationship of parameters before and after hemodialysis. This study enrolled 161 maintenance hemodialysis patients. PAD was defined as ABI < 0.9 in either leg. HRV was performed to assess changes before and after hemodialysis. The change in HRV (△HRV) was defined as post-hemodialysis HRV minus pre-hemodialysis HRV. Patients’ clinical parameters were collected from the dialysis records. All HRV parameters except high frequency (HF) % were lower in patients with PAD than patients without PAD, though not achieving significant level. In patients without PAD, HF (P = 0.013), low frequency (LF) % (P = 0.028) and LF/HF (P = 0.034) were significantly elevated after hemodialysis, whereas no significant HRV parameters change was noted in patients with PAD. Serum intact parathyroid hormone was independently associated with △HF (β = -0.970, P = 0.032) and △LF% (β = -12.609, P = 0.049). Uric acid level (β = -0.154, P = 0.027) was negatively associated with △LF/HF in patients without PAD. Our results demonstrated that some of the HRV parameters were significantly increased after hemodialysis in patients without PAD, but not in patients with PAD, reflecting a state of impaired sympatho-vagal equilibrium. Severity of secondary hyperparathyroidism and hyperuricemia contributed to lesser HRV parameters increase after hemodialysis in patients without PAD.

Cardiovascular autonomic neuropathy in type 2 diabetes mellitus patients with peripheral artery disease

OBJECTIVE

To evaluate possible associations between cardiovascular autonomic dysfunction and peripheral artery disease (PAD) in patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

In this cross-sectional study, 67 patients with type 2 diabetes were included. PAD was identified by Doppler ultrasonography: systolic ankle-brachial pressure index <0.9. Cardiovascular autonomic function, besides five conventional cardiovascular autonomic function tests, was assessed by heart rate variability (HRV; 24-h ambulatory ECG recording) in time and frequency domains (spectral analyses) and three dimensional return maps. Power spectral analyses (PSA) were quantified in low frequency (LF), high frequency (HF), and very low frequency.

RESULTS

Patients with PAD (n = 30) had longer diabetes duration, higher systolic blood pressure (BP), waist-to-hip ratio, HbA1C test, and urinary albumin excretion (UAE) than patients without PAD. Most HRV indices in time domain were lower in patients with than without PAD. These patients also had lower PSA indices (LF=0.19±0.07 vs. 0.29±0.11 n.u.; LF/HF ratio=1.98±0.9 vs. 3.35±1.83; P< 0.001) and indices of sympathetic (three-dimensional return map: P1-night 61.7±9.4 vs. 66.8±9.7; P=0.04) and vagal (24-h P2 54.5±15.2 vs. 62.7±2.9; P< 0.02) activities (arbitrary units) than patients without PAD. Multivariate logistic regression analyses, adjusted for systolic BP, DM duration, HbA1C test, and UAE, confirmed the associations between impaired autonomic modulation and PAD, except for P1 index.

CONCLUSION

In conclusion, patients with type 2 diabetes with PAD had lower HRV indices than patients without PAD, reflecting a dysfunction of cardiovascular autonomic modulation.

Power spectral analyses of index finger skin blood perfusion in carpal tunnel syndrome and diabetic polyneuropathy

The main purpose of this study was to investigate the applicability of frequency domain analysis on laser Doppler flowmetry (LDF) data recorded from the index fingers of patients with carpal tunnel syndrome (CTS) and diabetic polyneuropathy (DPN). Patients with numbness of the palm were recruited and grouped according to the results of electrophysiological examinations into 2×2 groups by the existence or nonexistence of CTS and/or DPN. Skin blood perfusion was recorded by LDF in both the neutral position and the maximally flexed position (the Phalen test). S-transformation was utilized to decompose the recorded data into frequency bands, and the relative band power and power dispersion were calculated. Analysis of variance was used to test the effects of DPN, CTS, and the Phalen test results. The results showed that (1) DPN decreased the absolute power and the relative power in some frequency bands in both positions and CTS increased the power dispersion of some frequency bands only during the Phalen test and (2) there was no difference in the LDF results between patients with positive or negative Phalen test results.

Fast and low-cost analysis of heart rate variability reveals vegetative alterations in noncomplicated diabetic patients

The aim of the present preliminary study was to describe a simple protocol for the analysis of the heart rate variability (HRV) that can reveal the different autonomic control between noncomplicated diabetic patients and normal subjects within 15 min. The power spectrum of the HRV was evaluated on 5-min-long electrocardiographic recordings in both the supine and the seated positions in 30 noncomplicated non-insulin-dependent diabetic (NIDDM) patients and in 30 healthy volunteers. In healthy subjects the low-frequency (LF) value was higher in seated position than in supine position, while in diabetic patients the LF value in seated position did not differ from that in supine position and did not differ from that in healthy subjects in supine position. The present work demonstrates that the protocol described reveals a different autonomic regulation of the heart rate in healthy subjects and in NIDDM patients even if there is no clinically evident autonomic neuropathy.

Long-term prognostic value of heart-rate recovery after treadmill testing in patients with diabetes mellitus

BACKGROUND

Heart-rate recovery (HRR) is considered to be an independent predictor of cardiac and all-cause mortality. We examined the long-term prognostic value of HRR in patients suffering from diabetes mellitus.

METHODS

In this study, we included 258 consecutive patients. Patients whose HRR value or myocardial perfusion imaging could have been influenced by factors other than myocardial ischaemia, were excluded. The value of HRR was defined as the decrease in the heart-rate from peak exercise to 1 min after the termination of the exercise. All patients underwent SPECT myocardial perfusion imaging combined with exercise testing. Cardiovascular death and non-fatal myocardial infarction were considered as hard cardiac events, while late revascularization procedures as soft events. Cox proportional-hazard models were applied to evaluate the association between HRR and the investigated outcome.

RESULTS

During the follow-up period (30.8+/-6.9 months), hard cardiac events occurred in 21 (8%) patients (15 with abnormal HRR value, p<0.001), while 35 (14%) patients underwent revascularization (31 with abnormal HRR value, p<0.001). Considering it as a continuous variable, HRR was a strong predictor for both hard cardiac (coefficient=-0.41, SE=0.052, p<0.001) and soft cardiac events (coefficient=-0.63, SE=0.058, p<0.001). After adjustments were made for potential confounders, including scintigraphic variables, abnormal HRR remained an independent predictor for hard and soft cardiac events (p<0.001).

CONCLUSION

Our results suggest that among patients with diabetes, a decreased HRR is a significant independent predictor of hard and soft cardiac events.

Análise de fatores associados à ulceração de extremidades em indivíduos diabéticos com neuropatia periférica

A neuropatia periférica é o principal fator de risco para ulceração em pé de indivíduos diabéticos. Este estudo testou a associação de doença arterial periférica (DAP) à ulceração do pé em amostra de pacientes com neuropatia sensório-motora simétrica distal e se marcadores inflamatórios subclínicos também se associariam a esse evento. Foram avaliados 32 indivíduos diabéticos tipo 2 com exame do monofilamento de 10 g alterado, estratificados em 2 grupos segundo a história ou presença de úlcera nas extremidades inferiores. O grupo "com úlcera" (n = 18) incluiu aqueles que apresentavam úlcera ativa ou cicatrizada, ou que tiveram alguma amputação em membro inferior decorrente de complicações da úlcera. Além do exame neurológico e monofilamento, foram submetidos a bioestesiometria, avaliação vascular com Doppler e exames laboratoriais. Os grupos foram semelhantes quanto à distribuição dos sexos, média de idade e tempo de diabetes. O grupo com úlcera apresentou valores médios de altura (1,70 ± 0,06 vs. 1,63 ± 0,11 m; p = 0,044) e limiar de percepção vibratória no maléolo medial (40,9 ± 13,0 vs. 30,6 ± 12,3 V; p = 0,040) mais elevados que o sem a úlcera. Os grupos não diferiram entre si quanto à média dos marcadores inflamatórios. A resposta do reflexo patelar foi também pior no grupo com úlcera (p = 0,047), no qual se observou maior proporção de indivíduos com o índice hálux-braquial alterado (p = 0,030) quando comparado ao sem úlcera. Conclui-se que a DAP está associada à presença de úlcera (atual ou pregressa) em membros inferiores de indivíduos diabéticos neuropatas. A pesquisa de alteração de fluxo de artérias digitais de membro inferior (no hálux) contribuiu para detectar tal associação. Associação de neuropatia ulcerada a marcadores inflamatórios não foi observada, não sendo possível excluí-la devido às limitações do tamanho da amostra. Estudos prospectivos deverão examinar a sensibilidade do índice hálux-braquial para identificar DAP em indivíduos diabéticos sob risco de ulceração.

Evaluation of abnormal heart-rate recovery after exercise testing in patients with diabetes mellitus: correlation with myocardial SPECT and chronotropic parameters

OBJECTIVE

Diabetes is associated with abnormal function of the autonomic nervous system, while autonomic dysfunction is related to attenuated heart-rate recovery (HRR) after exercise testing. The purpose of this study was to test whether HRR could be a useful index of myocardial ischaemia in patients suffering from diabetes mellitus.

METHODS

We included 206 consecutive patients in this study and excluded patients whose HRR value or the myocardial perfusion imaging could have been influenced by factors other than myocardial ischaemia. The value of HRR was defined as the decrease in the heart rate from peak exercise to 1 min after the termination of the exercise. All patients underwent SPECT myocardial perfusion imaging, combined with exercise testing and we calculated the summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) indexes.

RESULTS

Sixty patients had abnormal HRR value. A significant correlation was found between HRR 1 min after exercise and SSS (r=-0.64, P<0.001), SDS (r=0.56, P<0.001) and chronotropic variables. Patients with abnormal HRR value, had a higher frequency of other risk factors (besides diabetes) for CAD, were mostly taking cardioactive medications, had lower efficiency during treadmill testing, and presented more pathologic findings on the scintigram.

CONCLUSIONS

Our results suggest that myocardial ischaemia, as it is mainly assessed by myocardial perfusion imaging, has an important correlation with HRR in diabetic patients. HRR value 1 min after exercise may be considered as a useful index of the severity of myocardial ischaemia, in this cohort of patients.

High serum high-sensitivity C-reactive protein concentrations are associated with relative cardiac sympathetic overactivity during the early morning period in type 2 diabetic patients with metabolic syndrome

Sympathetic activation is associated with metabolic syndrome (MS) and increased risk of cardiovascular disease. The aim of this study was to investigate whether cardiac autonomic activity or sympathovagal balance, as estimated by a 24-hour power spectral analysis of heart rate variation, is associated with serum concentrations of high-sensitivity C-reactive protein (hs-CRP), a sensitive predictor for cardiovascular events, in type 2 diabetic patients with and without MS. We studied 104 type 2 diabetic patients (50 female and 54 male). The diagnosis of MS was based on the National Cholesterol Education Program Adult Treatment Panel III criteria. Based on the serum hs-CRP, diabetic patients were also divided into 3 groups: low risk (CRP < 1.0 mg/L), moderate risk (1.0 < or = CRP < or = 3.0), and high risk (CRP > 3.0). Heart rate variation was determined automatically every 5 minutes over 24 hours using an ambulatory Holter electrocardiographic recording. Power spectral analysis of the R-R intervals was performed by fast Fourier transformation. Low frequency (LF, both sympathetic and parasympathetic activities), high frequency (HF, pure parasympathetic activity), and the ratio of LF to HF, an index of sympathovagal balance, were used as indices of cardiac autonomic activity. Blood concentrations of hs-CRP, interleukin 6, and plasminogen activator inhibitor 1 were higher in diabetic patients with than in those without MS (P < .0001, P = .0056, and P < .0001, respectively). Both the 24-hour mean LF and the LF-to-HF ratio were also significantly higher in diabetic patients with than in those without MS (P = .0397 and P = .0483, respectively). The LF-to-HF ratio at 6:00 am was significantly higher in diabetic patients with a high CRP concentration than in those with a low or moderate CRP concentration (P < .001 and P < .01, respectively). Only urinary albumin and hs-CRP were independent factors predicting the LF-to-HF ratio at 6:00 am in diabetic patients. In conclusion, type 2 diabetic patients with MS have elevated markers of inflammation and evidence of cardiac sympathetic predominance. High serum concentrations of hs-CRP are associated with relative cardiac sympathetic overactivity during the early morning in type 2 diabetic patients.

Melatonin levels decrease in type 2 diabetic patients with cardiac autonomic neuropathy

The present study has been designed to determine melatonin levels in type 2 diabetic patients and test the relationship between the autonomic nervous system and melatonin dynamics. Thirty-six type 2 diabetic patients and 13 age-matched healthy subjects were recruited for the study. Circadian rhythm of melatonin secretion was assessed by measuring serum melatonin concentrations between 02:00-04:00 and 16:00-18:00 hr. Melatonin dynamics were re-evaluated with respect to autonomic nervous system in diabetic patients with autonomic neuropathy who were diagnosed by the cardiovascular reflex tests, heart rate variability (HRV), and 24-hr blood pressure monitoring. Nocturnal melatonin levels and the nocturnal melatonin surge were low in the diabetic group (P = 0.027 and 0.008 respectively). Patients with autonomic neuropathy revealed decreased melatonin levels both at night and during day when compared with healthy controls (P < 0.001 and 0.004 respectively) while the melatonin dynamics were similar to controls in patients without autonomic neuropathy. Nocturnal melatonin level was positively correlated with nocturnal high and low frequency components of HRV (P = 0.005 and 0.011 respectively) and systolic and diastolic blood pressures at night (P = 0.002 and 0.004 respectively) in patients with autonomic neuropathy. We found a negative correlation between nocturnal melatonin levels and the degree of systolic blood pressure decrease at night (r = -0.478, P = 0.045). As a conclusion this study has shown that circadian rhythm of melatonin secretion is blunted in type 2 diabetic patients and there is a complex relationship between various components of autonomic nervous system and melatonin secretion at night. Among the patients with autonomic neuropathy those with more preserved HRV and the systolic nondippers (<10% reduction in blood pressure during the night relative to daytime values) have more pronounced melatonin surge at night.

Heart rate variability in young patients with diabetes mellitus and healthy subjects explored by Poincaré and sequence plots

Autonomic neuropathy is a common complication of the diabetes mellitus (DM). The significance of its early diagnosis is very high because the mortality of the patients with this complication is elevated. Considering the effort to apply new mathematical methods to cardiac dysregulation diagnosis, the major aim of the study was to ascertain which of the new heart rate variability (HRV) parameters are different in young patients with DM type 1 compared with control group. The next aim was to assess the HRV changes during prolonged (40 min) supine rest. The heart rate was continuously recorded during supine rest in 17 young patients with DM type 1 (10 women, 7 men) aged 22.4 +/- 1.0 years (mean +/- SEM). The control group consisted of 17 healthy matched probands. The HRV (time/frequency domains, Poincare and sequence plots, sample entropy) was analysed in two intervals - T1 starting at fifth minute and T2 starting at 30th minute of supine rest. The major results of our study are: the reduced Poincare plot pattern measures in the young DM group; the lower percentage of points in the third quadrant of sequence plot (this parameter was not correlated with the mean heart rate) and significant changes in HRV during supine rest in DM group (in contrast to control subjects). In conclusion, HRV parameters based on nonlinear dynamics were able to distinguish cardiac dysregulation in young patients with DM from the control group. The percentage of points in the third quadrant of sequence plot provides information that is not dependent on mean heart rate. Poincare and sequence plots, together with the rate of HRV changes during supine rest, can provide clinically relevant information usable in diagnosis of the cardiac dysregulation.

Disparity of autonomic control in type 2 diabetes mellitus

AIMS/HYPOTHESIS

Acute insulinaemia activates the sympathetic drive in a nonuniform manner. The extent and nature of such activation in type 2 diabetic patients who do not have neuropathy have not yet been addressed despite evidence relating sympathetic activation to cardiovascular risk. We planned to determine the magnitude and extent of the sympathetic drive and its reflex responses in patients with type 2 diabetes and fasting hyperinsulinaemia.

METHODS

We measured resting muscle sympathetic nerve activity (MSNA) as the mean frequency of multi-unit bursts and single unit muscle sympathetic nerve activity (s-MSNA) in 17 overweight patients with type 2 diabetes and two matched normal control groups comprising 17 overweight and 16 normal-weight subjects. We also tested the MSNA and s-MSNA responses to cold pressor and isometric hand-grip tests, along with the effect of sympatho-vagal balance on heart period variability.

RESULTS

Both MSNA and s-MSNA in the group with type 2 diabetes (66+/-3.5 bursts/100 beats and 78+/-4.5 impulses/100 beats) were greater (at least p<0.0001) than in the overweight control group (42+/-2.6 bursts/100 beats and 48+/-3.4 impulses/100 beats) and normal-weight control group (43+/-6.2 bursts/100 beats and 51+/-7.1 impulses/100 beats), though the three groups had similar reflex responses, baroreflex sensitivity and sympatho-vagal balance controlling the heart period.

CONCLUSIONS/INTERPRETATION

The patients with type 2 diabetes had no evidence of impaired reflex or autonomic control of heart period variability at a time when there was central sympathetic activation to the periphery. Furthermore, being overweight itself was not associated with sympathetic activation.

Adiponectin concentrations in sera from patients with type 2 diabetes are negatively associated with sympathovagal balance as evaluated by power spectral analysis of heart rate variation

OBJECTIVE

To investigate whether cardiac autonomic activity, particularly sympathovagal balance as estimated by power spectral analysis (PSA) of heart rate variation (HRV), is associated with serum adiponectin concentrations in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied 105 patients with type 2 diabetes (51 women and 54 men). Serum adiponectin concentrations were measured by sandwich enzyme-linked immunosorbent assay. HRV was determined automatically every 5 min over 24 h using Holter electrocardiographic recording. PSA of R-R intervals was performed using fast Fourier transformation. Low-frequency (both sympathetic and parasympathetic activities), high- frequency (pure parasympathetic activity), and the ratio of low-frequency-to-high-frequency power (LF-to-HF ratio), an index of sympathovagal balance, were used as indexes of cardiac autonomic activity.

RESULTS

We found no significant correlation between serum adiponectin and low-frequency or high-frequency power in patients with diabetes. Serum adiponectin concentration correlated negatively with the 24-h LF-to-HF ratio (r = -0.343, P = 0.0009) and creatinine clearance (r = -0.411, P < 0.0001). Serum adiponectin concentrations were significantly higher in patients with overt albuminuria than in those with normoalbuminuria or microalbuminuria. In multivariate analysis controlling for sex, BMI, glycemic control, lipid profile, and renal function, serum adiponectin concentration showed an independent negative association with 24-h LF-to-HF ratio (beta = -0.332, P = 0.020). Furthermore, sex, HDL cholesterol, and renal function retained significant influence on the serum adiponectin concentration in patients with diabetes.

CONCLUSIONS

Sympathovagal balance favoring relative sympathetic activation was associated with low serum concentrations of adiponectin in patients with type 2 diabetes.

Relationship between sympathetic skin response and power spectral analysis of heart rate variation in patients with type 2 diabetes

We measured sympathetic skin response (SSR), a measure of sympathetic sudomotor function, and compared SSR with other quantitative neurological tests including power spectral analysis (PSA) of heart rate variations in 60 type 2 diabetic subjects. SSR was detected in all 20 age-matched healthy subjects but was absent in 17 patients with type 2 diabetes (28%) (P<.01). Even after exclusion of diabetic patients with absent SSR, the SSR amplitude in diabetic patients was significantly lower than in healthy subjects (P<.05). Both the low frequency power of R-R intervals, which reflects both cardiac sympathetic and parasympathetic function, and the postural fall in systolic blood pressure were significantly lower in the diabetic patients with absent SSR than in those with present SSR (P<.05 and.001, respectively). However, we found no significant difference in the high frequency power of R-R intervals, which reflects accurately cardiac parasympathetic function, between the diabetic patients with absent SSR and those with present SSR. In the diabetic patients with present SSR, SSR amplitude was also positively correlated with the postural fall in systolic blood pressure, low-frequency (LF) power, and high-frequency (HF) power. These results suggest that SSR is a useful and sensitive method for evaluating diabetic autonomic neuropathy, and that sympathetic sudomotor neuropathy may be preceded by cardiac parasympathetic neuropathy in patients with type 2 diabetes.

Clinical diagnosis of diabetic polyneuropathy with the diabetic neuropathy symptom and diabetic neuropathy examination scores

OBJECTIVE

To evaluate the discriminative power of the Diabetic Neuropathy Symptom (DNS) and Diabetic Neuropathy Examination (DNE) scores for diagnosing diabetic polyneuropathy (PNP), as well as their relation with cardiovascular autonomic function testing (cAFT) and electro-diagnostic studies (EDS).

RESEARCH DESIGN AND METHODS

Three groups (matched for age and sex) were selected: 24 diabetic patients with neuropathic foot ulcers (DU), 24 diabetic patients without clinical neuropathy or ulcers (DC), and 21 control subjects without diabetes (C). In all participants, the DNS and DNE scores were assessed and cAFT (heart rate variability [HRV], baroreflex sensitivity [BRS]), and EDS were performed (Nerve Conduction Sum [NCS] score; muscle fiber conduction velocity: fastest/slowest ratio [F/S ratio]).

RESULTS

Both the DNS and the DNE scores discriminated between the DU and DC groups significantly (P < 0.001). The DNE score even discriminated between DC and C (P < 0.05). Spearman's correlation coefficients between both DNS and DNE scores and cAFT (HRV -0.42 and -0.44; BRS -0.30 and -0.29, respectively) and EDS (NCS 0.51 and 0.62; F/S ratio 0.44 and 0.62, respectively) were high. Odds ratios were calculated for both DNS and DNE scores with cAFT (HRV 4.4 and 5.7; BRS 20.7 and 14.2, respectively) and EDS (NCS 5.6 and 16.8; F/S ratio 7.2 and 18.8, respectively).

CONCLUSIONS

The DNS and DNE scores are able to discriminate between patients with and without PNP and are strongly related to cAFT and EDS. This further confirms the strength of the DNS and DNE scores in diagnosing diabetic PNP in daily clinical practice.

Cardiac autonomic nervous dysfunction in diabetic patients with a mitochondrial DNA mutation: assessment by heart rate variability

OBJECTIVE

To elucidate the degree and characteristics of cardiac autonomic nervous dysfunction in diabetic patients associated with a mitochondrial DNA mutation at base pair 3243.

RESEARCH DESIGN AND METHODS

We investigated heart rate variability using 24-h Holter monitoring in 10 diabetic patients with the mutation compared with 55 ordinary diabetic patients and 45 nondiabetic control subjects.

RESULTS

Age and sex were similar in the three groups. Between patients with the mutation and ordinary diabetic patients, the duration of diabetes and blood glycemic levels were not different. In the time domain analysis of heart rate variability, patients with the mutation and ordinary diabetic patients had significantly smaller SDNN index and pNN50 than control subjects. Compared with ordinary diabetic patients, patients with the mutation had smaller SDNN index (P < 0.02), but rMSSD and pNN50 were not different. In the frequency domain analysis, total, low frequency (LF), and high frequency (HF) spectra were significantly smaller in patients with the mutation and ordinary diabetic patients than in control subjects. Compared with ordinary diabetic patients, patients with the mutation had smaller total and LF spectra (P < 0.02). However, HF spectra were not significantly different. Notably, the LF/HF spectra ratio was lower in patients with the mutation than in ordinary diabetic patients and control subjects (P < 0.05), but this ratio was similar in ordinary diabetic patients and control subjects.

CONCLUSIONS

Our results suggest that diabetic patients with the mitochondrial DNA mutation have more severely impaired cardiac autonomic nervous function with sympathovagal imbalance, as compared with ordinary diabetic patients.

Relationship of medial arterial calcinosis to autonomic neuropathy and adverse outcomes in a diabetic veteran population

STATEMENT OF THE PROBLEM

Medial arterial calcinosis (MAC) is associated with neuropathy, amputation, and mortality through an unknown mechanism. We hypothesized that MAC was a marker of autonomic neuropathy rather than a risk factor and that the outcomes were due to autonomic neuropathy.

METHODS

All subjects in an ongoing prospective study of diabetic foot conditions in a diabetic veteran cohort who received a foot radiograph between 11/7/90 and 11/5/93 were included. Autonomic neuropathy measured as either heart rate variability with timed respiration or postural hypotension. A logistic model predicted the presence of MAC at baseline and Cox proportional models assessed the relative contribution of autonomic neuropathy and traditional risk factors for the outcomes of ulceration, amputation, and death.

RESULTS

MAC was identified in 181 subjects, no MAC in 253 subjects, and 39 were excluded due to disagreement between observers. Both measures of autonomic neuropathy were independent predictors of MAC at baseline, even after adjustment for vibration sensation loss in a logistic model. MAC was associated with an increased risk for ulceration (hazards ratio, HR: 2.1, 95% confidence intervals, CI, 1.4-3.1), amputation (HR 3.3, 95% CI 1.5-7.4), and mortality (HR 1.6, 95% CI 1.1-2.2). The addition of either autonomic measure of neuropathy did not change the MAC HR or significantly improved the fit of the model.

CONCLUSIONS

Our hypothesis that the excess mortality, amputation, and ulceration in persons with MAC could be explained by autonomic neuropathy measured as postural hypotension or heart rate variability with measured respiration was not supported.

Association of fasting plasma glucose with heart rate recovery in healthy adults: a population-based study

Diabetes is associated with abnormal autonomic function and increased mortality. Abnormal heart rate recovery after exercise, a measure of autonomic dysfunction, is also associated with increased mortality. The objective of this study was to determine the association of fasting plasma glucose with abnormal heart rate recovery and its prognostic importance in healthy adults. We studied 5,190 healthy adults who did not have medically treated diabetes (mean age 45 years, 39% women), were enrolled in the Lipid Research Clinics' Prevalence Study, and underwent exercise testing. Heart rate recovery was defined as the change from peak heart rate to that after 2 min of recovery; an abnormal value was < or = 42 bpm. All-cause mortality was assessed over 12 years. A total of 504 participants (10%) had impaired fasting glucose, and 131 (3%) had untreated diabetes. An abnormal heart rate recovery was found in 1,699 (33%). Compared with participants who had normal fasting plasma glucose, abnormal heart rate recovery was more common among those with impaired fasting glucose (42 vs. 31%; relative risk, 1.34; 95% confidence interval [CI], 1.20--1.50; P < 0.0001) and those with diabetes (50 vs. 31%; relative risk, 1.61; 95% CI, 1.35--1.92; P < 0.0001). Fasting plasma glucose remained an independent predictor of abnormal heart rate recovery even after adjustment for age, sex, and other confounders (P = 0.0003). An abnormal heart rate recovery added to impaired fasting plasma glucose for the prediction of death. Fasting plasma glucose is strongly and independently associated with abnormal heart rate recovery, even at nondiabetic levels.

Elevation of von Willebrand factor in plasma in diabetic patients with neuropathic foot ulceration

AIMS

The present study examines the relationship between markers of endothelial dysfunction and diabetic neuropathy or consequent neuropathic foot ulceration in patients with Type 2 diabetes mellitus.

METHODS

We studied 65 Type 2 diabetic patients including 25 diabetic patients without neuropathy, 27 with neuropathy but no history of foot ulceration, and 13 with neuropathic ulceration. Plasma concentrations of von Willebrand factor (vWF) and soluble thrombomodulin (TM), measures of endothelial dysfunction, were determined by enzyme immunoassays. We performed various tests quantifying aspects of diabetic neuropathy including vibration perception threshold (VPT; for sensory neuropathy), coefficient of variation of R-R intervals (CVR-R; for cardiac autonomic neuropathy), and cold-induced vasodilation in the great toe for peripheral sympathetic neuropathy.

RESULTS

CVR-R and cold-induced vasodilation were significantly diminished in patients with neuropathic foot ulceration compared with patients with neuropathy but no history of foot ulceration. Plasma vWF concentrations were positively correlated with VPT and cold-induced vasodilation test, and were inversely correlated with CVR-R. Multivariate analysis disclosed that VPT and percentage vasodilation were independent factors for plasma vWF. Plasma vWF was significantly elevated in patients with foot ulceration compared with patients without neuropathy or those with neuropathy but not foot ulceration. However, plasma TM concentrations did not differ between the three groups.

CONCLUSIONS

Diabetic patients with neuropathic foot ulceration had severe impairment of cardiac autonomic and peripheral sympathetic nerves. Elevation of vWF in plasma was associated with neuropathic foot ulceration, linking endothelial dysfunction to foot ulceration.

Neurophysiological studies of thin myelinated (A delta) and unmyelinated (C) fibers: application to peripheral neuropathies

Dysfunction of small fibers may appear in isolation or associated with large fiber lesions. In some acute neuropathies, such as pandysautonomia, small-fiber impairment is relatively pure but it may also appear in disorders with prominent somatic damage, such as Guillain-Barré syndrome, in which autonomic failure worsens the prognosis. At the present time, chronic idiopathic distal small-fiber neuropathy is diagnosed more frequently, and in some prevalent disorders, such as diabetic or amyloidotic polyneuropathies, small-fiber dysfunction is very noticeable. In pure autonomic failure, a peripheral autonomic failure exists, distinguishing it from multiple-system atrophy. Complex regional pain syndrome is a severe condition in which small fibers are responsible for disabling signs and symptoms, and only instrumental recordings lead to the proper treatment. Standard neurophysiological techniques evaluate large myelinated fibers exclusively. Small-fiber polyneuropathy has been considered as a type of somatic neuropathy, but thin myelinated and unmyelinated fibers are responsible not only for temperature and pain perception but also autonomic function. For instance, full autonomic evaluation is needed in some clinical situations such as autonomic failure in the elderly or orthostatic intolerance syndrome. To evaluate small-fiber impairment we need a battery of sensitive, reproducible, specific and noninvasive tests covering somatic and autonomic systems. In this review, we describe and analyze a number of neurophysiological techniques used to diagnose and characterize small-fiber dysfunction in humans. These include cardiovascular monitoring, sudomotor testing, pupillary responses and quantitative sensory tests, and also to some extent thermography and laser evoked potentials. The use of such techniques has proven useful not only for diagnosis, but also to guide adequate therapy and optimize follow-up.