Vincenza Spallone

Diabetic neuropathies: Update on definitions, diagnostic criteria, estimation of severity, and treatments

Preceding the joint meeting of the 19th annual Diabetic Neuropathy Study Group of the European Association for the Study of Diabetes (NEURODIAB) and the 8th International Symposium on Diabetic Neuropathy in Toronto, Canada, 13–18 October 2009, expert panels were convened to provide updates on classification, definitions, diagnostic criteria, and treatments of diabetic peripheral neuropathies (DPNs), autonomic neuropathy, painful DPNs, and structural alterations in DPNs.

Cardiovascular autonomic neuropathy in diabetes: clinical impact, assessment, diagnosis, and management

The Cardiovascular Autonomic Neuropathy (CAN) Subcommittee of the Toronto Consensus Panel on Diabetic Neuropathy worked to update CAN guidelines, with regard to epidemiology, clinical impact, diagnosis, usefulness of CAN testing, and management. CAN is the impairment of cardiovascular autonomic control in the setting of diabetes after exclusion of other causes. The prevalence of confirmed CAN is around 20%, and increases up to 65% with age and diabetes duration. Established risk factors for CAN are glycaemic control in type 1 and a combination of hypertension, dyslipidaemia, obesity, and glycaemic control in type 2 diabetes. CAN is a risk marker of mortality and cardiovascular morbidity, and possibly a progression promoter of diabetic nephropathy. Criteria for CAN diagnosis and staging are: (1) one abnormal cardiovagal test result identifies possible or early CAN; (2) at least two abnormal cardiovagal test results are required for definite or confirmed CAN; and (3) the presence of orthostatic hypotension in addition to abnormal heart rate test results identifies severe or advanced CAN. Progressive stages of CAN are associated with increasingly worse prognosis. CAN assessment is relevant in clinical practice for (1) diagnosis of CAN clinical forms, (2) detection and tailored treatment of CAN clinical correlates (e.g. tachycardia, orthostatic hypotension, non‐dipping, QT interval prolongation), (3) risk stratification for diabetic complications and cardiovascular morbidity and mortality, and (4) modulation of targets of diabetes therapy. Evidence on the cost‐effectiveness of CAN testing is lacking. Apart from the preventive role of intensive glycaemic control in type 1 diabetes, recommendations cannot be made for most therapeutic approaches to CAN. Copyright

Relationship Between the Circadian Rhythms of Blood Pressure and Sympathovagal Balance in Diabetic Autonomic Neuropathy

In diabetic autonomic neuropathy, abnormal circadian patterns of blood pressure and sympathovagal balance with reduced fall of blood pressure and prevalence of sympathetic activity during the night have been described. To correlate the abnormalities of blood pressure to those of sympathovagal balance, we simultaneously performed 24-h noninvasive monitoring of blood pressure and ECG in 25 diabetic patients (45.6 ± 13.6 yr of age with a 17.6 ± 9.1 yr duration of diabetes) with various degrees of cardiovascular reflex impairment. Autoregressive power spectrum analysis of RR interval variability was applied to 24-h ECG recordings to obtain for day and night periods the mean power of low- (0.03–0.15 Hz) and high-frequency (0.18–0.40 Hz) components, which are relative markers of sympathetic and vagal activity, respectively, and their ratio (low frequency/high frequency), assumed as index of sympathovagal balance. Diabetic patients showed a lower percentage of day-night change in systolic blood pressure (9 ± 5.48 vs. 11.6 ± 4.78%, P < 0.037), a lower day low frequency (5.9 ± 0.81 vs. 6.62 ± 0.73 In-ms2 P < 0.001), a lower night high frequency (6.06 ± 0.71 vs. 6.52 ± 0.85 In-ms2 P < 0.05), a lower day low frequency:high frequency ratio (1.82 ± 1.77 vs. 3.05 ± 1.82, P < 0.01), and a lower percentage of day-night change in low-frequency:high frequency ratio (– 13.4 ± 109.9 vs. 28.7 ± 29.7%, P < 0.05), when compared with control subjects. Day-night change in low frequency:high frequency ratio correlated to day-night change in systolic blood pressure (r = 0.52, P < 0.01) and diastolic blood pressure (r = 0.48, P < 0.015). In conclusion, in diabetic patients the degree of loss in day-night rhythm of blood pressure is associated with a proportional nocturnal sympathetic predominance. Decreased blood pressure fall combined with relative sympathetic prevalence during the night might represent a risk factor for cardiovascular accidents and could modify the circadian pattern of cardiovascular events in the diabetic population.

Relationship between autonomic neuropathy, 24-h blood pressure profile, and nephropathy in normotensive IDDM patients.

OBJECTIVE To evaluate the relationship between autonomic neuropathy, nephropathy, and 24-h blood pressure (BP) pattern in insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS We studied 30 normotensive IDDM patients without overt nephropathy, divided into two groups and matched for age, duration of diabetes, and HbA1 according to the presence of cardiovascular autonomic neuropathy. We simultaneously measured 24-h BP and urinary albumin excretion rate (UAE) on urine collections timed overnight and at 2-h intervals during the day. RESULTS Mean day and night systolic and diastolic BP values did not significantly differ between the groups. Mean night albuminuria was significantly higher in patients with autonomic neuropathy than in those without (61.4 ± 104.6 [mean ± SD] vs. 16 ± 25.2 μg/min, P < 0.04). The percentages day-night changes in systolic BP, diastolic BP, and UAE were significantly lower in neuropathic patients (systolic BP: 2.4 ± 7.7 vs. 9.6 ± 4.2%, P < 0.001; diastolic BP: 8.4 ± 6.9 vs. 15.5 ± 5.4%, P < 0.002; UAE: – 8 ± 99.4 vs. 49.3 ± 29.4%, P < 0.02) and were inversely related to autonomic score, index of autonomic neuropathy degree (r = –0.54, P < 0.002; r = –0.58, P < 0.001; and r = –0.53, P < 0.005, respectively). In patients with autonomic neuropathy, 2-h day periods and day and night UAE were more strongly related, respectively, to mean 2-h day periods (r = 0.58, P < 0.0001), day systolic BP (r = 0.67, P < 0.04), and night systolic BP (r = 0.69, P < 0.04) than in patients without autonomic neuropathy (2-h day periods: r = 0.32, P < 0.001; day: r = 0.37, NS; night: r = 0.35, NS). CONCLUSIONS Autonomic neuropathy in IDDM patients is associated with reduced nocturnal falls in BP and UAE and with a stronger relationship of UAE to systolic BP. We suggest a pathogenetic role of autonomic neuropathy in the development of diabetic nephropathy through changes in nocturnal glomerular function and by enhanced kidney vulnerability to hemodynamic effects of BP.

Diagnosis of Cardiovascular Autonomic Neuropathy in Diabetes

The utility of standard cardiovascular tests for diagnosis of cardiac autonomie neuropathy in diabetes has been well documented. Attention must be paid to standardizing the procedure with regard to time of day, metabolic status, distance from meal and insulin, coffee and smoking avoidance, and patients collaboration. In the presence of cardiovascular disease or drugs affecting the cardiovascular or autonomic nervous system, some caution is needed in interpreting the results. More recent reflex tests, which evaluate mainly sympathetic or baroreflex activity, despite their ability to detect early autonomic involvement, lack sufficient standardization and still need to be proved as valid alternatives. Of the different methods of measuring heart rate variability, spectral analysis has a greater ability to differentiate vagal and sympathetic modulation of heart rate than do time-domain methods. However, since these latter methods are easier and more widely available, they can be used as a screening approach. Twenty-four-hour evaluation of heart rate variability provides data on the circadian rhythm of sympathovagal activity, which can be affected earlier than and differently from cardiovascular reflex tests. Information obtained could have prognostic implications in terms of cardiovascular morbidity and mortality and offer therapeutic opportunities. However, a wide consensus on many technical aspects of both time-domain and frequency-domain methods is needed. Furthermore, large prospective studies in the diabetic population to assess the prognostic value of 24-h heart rate variability parameters on cardiovascular morbidity and mortality are lacking. Recently, I123 meta-iodobenzylguanidine (MIBG) scintigraphy has documented abnormalities of sympathetic myocardial innervation also in newly diagnosed IDDM. The meaning of this finding, whether it is an expression of functional or structural defects, needs to be clarified. Preliminary data point to a possible pathogenetic meaning of the known association between autonomic neuropathy and other diabetic complications. This area of investigation could provide useful insights into the complex and multifactorial pathogenesis of diabetic complications.

Long-Term Outcomes of Diabetic Patients With Critical Limb Ischemia Followed in a Tertiary Referral Diabetic Foot Clinic

OBJECTIVE We describe the long-term outcomes of 510 diabetic patients with critical limb ischemia (CLI) and an active foot ulcer or gangrene, seen at the University Hospital of Rome Tor Vergata, a tertiary care clinic. RESEARCH DESIGN AND METHODS These patients were seen between November 2002 and November 2007 (mean follow-up 20 ± 13 months [range 1–66 months]). The Texas Wound Classification was used to grade these wounds that were either class C (ischemia) and D (ischemia+infection) and grade 2–3 (deep–very deep). This comprehensive treatment protocol includes rapid and extensive initial debridement, aggressive use of peripheral percutaneous angioplasty, empirical intravenous antibiotic therapy, and strict follow-up. RESULTS The protocol was totally applied (with percutaneous angioplasty [PA+]) in 456 (89.4%) patients and partially (without percutaneous angioplasty [PA−]) in 54 (10.6%) patients. Outcomes for the whole group and PA+ and PA− patients are, respectively: healing, n = 310 (60.8%), n = 284 (62.3%), and n = 26 (48.1%); major amputation, n = 80 (15.7%), n = 67 (14.7%), and n = 13 (24.1%); death, n = 83 (16.25%), n = 68 (14.9%), and n = 15 (27.8%); and nonhealing, n = 37 (7.25%), n = 37 (8.1%), and n = 0 (0%) (χ2 <0.0009). Predicting variables at multivariate analysis were the following: for healing, ulcer dimension, infection, and ischemic heart disease; and for major amputation, ulcer dimension, number of minor amputations, and age. Additional predicting variables for PA+ patients were the following: for healing, transcutaneous oxygen tension [ΔTcPo2]; and for major amputation, basal TcPo2, basal A1C, ΔTcPo2, and percutaneous angioplasty technical failure. CONCLUSIONS Early diagnosis of CLI, aggressive treatment of infection, and extensive use of percutaneous angioplasty in ischemic affected ulcers offers improved outcome for many previously at-risk limbs. Ulcer size >5 cm2 indicates a reduced chance of healing and increased risk of major amputation. It was thought that all ulcers warrant aggressive treatment including percutaneous angioplasty and that treatment should be considered even for small ischemic ulcers.

Methods of investigation for cardiac autonomic dysfunction in human research studies

This consensus document provides evidence‐based guidelines regarding the evaluation of diabetic cardiovascular autonomic neuropathy (CAN) for human research studies; the guidelines are the result of the work of the CAN Subcommittee of the Toronto Diabetic Neuropathy Expert Group. The subcommittee critically reviewed the limitations and strengths of the available diagnostic approaches for CAN and the need for developing new tests for autonomic function.

Validation of DN4 as a screening tool for neuropathic pain in painful diabetic polyneuropathy.

Diabet. Med. 29, 578–585 (2012)

Autonomic neuropathy and cardiovascular risk factors in insulin-dependent and non insulin-dependent diabetes

In 97 IDDM and 64 NIDDM patients aged under 65 years, we evaluated the relationship between autonomic neuropathy (AN) and retinopathy, nephropathy, glycemic control and cardiovascular risk factors. Diabetes duration and HbA1 were significantly higher and body mass index was significantly lower in IDDM patients with AN compared to those without. In NIDDM only age was significantly higher in neuropathic patients. AN was associated with retinopathy in both IDDM (chi2 = 10, P < 0.03) and NIDDM patients (chi2 = 14, P < 0.007), while only in IDDM albumin excretion was significantly higher in patients with AN. Blood pressure (BP) was significantly higher in both IDDM and NIDDM patients with AN compared to those without. There were no differences in smoking and serum lipids between patients with and those without AN. We performed a multiple regression analysis using autonomic score, index of cardiovascular tests impairment, as the dependent variable and age, diabetes duration, body mass index, HbA1, albumin excretion, cholesterolemia, triglyceridemia, systolic BP, and retinopathy as independent variables. With this model in IDDM autonomic score was only related to body mass index (r = -0.29, P < 0.05), to HbA1 (r = 0.46, P < 0.001), and to systolic BP (r = 0.24, P < 0.05), while in NIDDM it was only related to systolic BP (r = 0.54, P < 0.001). In conclusion, AN was related to age in NIDDM, and to diabetes duration and glycemic control in IDDM. AN was associated with retinopathy, with nephropathy (only in IDDM), and with BP levels, but not with dyslipidemia, smoking, or obesity. Excess mortality rate observed in diabetic AN cannot be referred to an association with cardiovascular risk factors.

A simple new non‐invasive sweat indicator test for the diagnosis of diabetic neuropathy

A simple non‐invasive indicator test (Neuropad®) has been developed for the assessment of sweating and, hence, cholinergic innervation in the diabetic foot. The present review summarizes current knowledge on this diagnostic test. The diagnostic ability of this test is based on a colour change from blue to pink at 10 min, with excellent reproducibility, which lends itself to patient self‐examination. It has a high sensitivity (65.1–100%) and negative predictive value (63–100%), with moderate specificity (32–78.5%) and positive predictive value (23.3–93.2%) for the diagnosis of diabetic peripheral neuropathy. It also has moderate to high sensitivity (59.1–89%) and negative predictive value (64.7–91%), but low to moderate specificity (27–78%) and positive predictive value (24–48.6%) for the diagnosis of diabetic cardiac autonomic neuropathy. There are some data to suggest that Neuropad can detect early diabetic neuropathy, but this needs further evaluation. It remains to be established whether this test can predict foot ulceration and amputation, thereby contributing to the identification of high‐risk patients.