Correlation of retinal neurodegeneration with measures of peripheral autonomic neuropathy in type 1 diabetes.

PURPOSE: To evaluate the relationship of neuroretinal layer thickness with sensitive measures of cardiovascular autonomic neuropathy in diabetic patients with non-proliferative diabetic retinopathy (NPDR). METHODS: Twenty-seven eyes of 27 patients with type 1 diabetes presenting with mild-to-moderate NPDR were compared to 27 healthy control (HC) eyes matched for age and gender. The total macular volume (TMV) and the volumes of individual neurosensory layers in the macula were analysed from spectral domain optical coherence tomography using automated layer segmentation. Cardiovascular autonomic regulation was assessed by short-term power spectrum analysis of heart rate variability (HRV) before, during and after an orthostatic challenge. RESULTS: The patients had an age of 46 ± 12 years and diabetes since 28 ± 9 years. Diastolic and mean arterial pressure was lower in the patients compared to HCs. TMV (r = 0.58, p = 0.002), inner plexiform layer volume (IPLV; r = 0.39, p = 0.047) and inner nuclear layer volume (INLV; r = 0.60, p = 0.001) were associated with reduced recovery of low-frequency (LF) spectral power of HRV after orthostatic load in diabetic patients but not in HCs. The response of LF spectral power during the orthostatic manoeuvre was blunted in patients compared to HCs (p = 0.02). Diabetes duration was negatively associated with TMV and INLV, whereas IPLV was significantly reduced in eyes with moderate NPDR compared to HCs. CONCLUSION: The results indicate a correlation between inner retinal tissue loss and diminished autonomic regulation in type 1 diabetic patients with mild-to-moderate NPDR. The observed changes can be interpreted as congruent early signs of retinal and systemic neuropathy in diabetes.

Non-contact radiofrequency-induced reduction of subcutaneous abdominal fat correlates with initial cardiovascular autonomic balance and fat tissue hormones: safety analysis.

BACKGROUND AND OBJECTIVE: The non-invasive reduction of subcutaneous abdominal fat became popular in the last decade. Radiofrequency (RF), non-contact, selective-field device Vanquish® has been developed to selectively induce deep fat tissue heating to reduce waist circumference. Our analysis evaluates immediate and sustained effects of this treatment on cardiovascular autonomic function and on selected metabolic parameters. Study design/ patients and methods: A retrospective proof-of-concept analysis of RF treatment effects was conducted in 20 individuals with metabolic syndrome, to reduce the subcutaneous abdominal fat. Four 30-minutes treatment sessions (manufacturer´s standard protocol) were performed in 1-week intervals. Vital signs, ECG, lab screening, body composition, subcutaneous fat thickness and spectral analysis of heart rate variability (HRV) have been examined before, after the 1 (st) and 4 (th) treatment, and at follow-up visits 1 month and 3 months after the treatment. RESULTS: The RF treatment led to a significant reduction of abdominal circumference after the 4 (th) session (p<0.001), and during follow-up after 1 and 3 months (p<0.001 and p<0.02, resp.). There was a significant correlation (r=-0.58, p=0.007) between reduction of abdominal circumference and initial very-low frequency (VLF) spectral power at 1 month follow-up. A significant increase of cumulative spectral power in low frequency (p=0.02) and reduction in high frequency (p=0.05) band have been observed immediately (20 +14 minutes) after the treatment. On the contrary, no sustained impact on autonomic balance has been recorded 39 +18 days after the treatment. A significant correlation between the initial adiponectin values and immediate autonomic response to one treatment was observed in VLF and total spectral bands (r>0.59, p<0.04). CONCLUSIONS: Our analysis shows that the selective-field RF treatment is safe and efficient for reduction of subcutaneous abdominal fat. While the treatment increases the immediate sympathetic response of the body to deep tissue heating, no sustained change in autonomic function could be recorded at 1 month follow-up. The observed correlation between initial VLF spectral power and waist circumference reduction at follow-up, as well as the association of initial adiponectin values and immediate autonomic response to the treatment might be instrumental for decisions on body contouring strategies.

Effects of guided breathing on blood pressure and heart rate variability in hypertensive diabetic patients.

OBJECTIVE: Our aim was to investigate medium-term effects of device-guided breathing on blood pressure (BP) and its capacity to improve the cardiovascular autonomic balance in hypertensive diabetic patients. This feasibility study was conceived as a proof-of-concept trial under real life conditions for justification of further investigations. METHODS: A randomized, controlled study (RCT) of the effects of device-guided slow breathing on top of usual care against usual care alone (including non-pharmacological and pharmacological treatment). The intervention included 12-min sessions of guided breathing performed daily for 8 weeks. Treatment effects were assessed with ambulatory blood pressure monitoring (24h ABPM) and with spectral analysis of short-term heart rate variability (HRV) obtained during standardized modified orthostatic load. Thirty-two subjects with diabetes and antihypertensive therapy were randomly assigned to both study groups. RESULTS: After 8 weeks of guided breathing, significant reductions were demonstrated in 24 h systolic BP (x±SEM: 126.1±3.0 vs 123.2±2.7 mmHg, p=0.01), and in 24 h pulse pressure (PP, 53.6±2.6 vs. 51.3±2.5 mmHg, p=0.01), whereas no significant impact in the control group was shown. The differences in treatment effects (delta mmHg, RESPeRATE® vs control) were significant only for PP (-2.3±0.8 vs +0.2±1.2 mmHg, p<0.05). Strong baseline dependence of treatment effects (delta systolic BP) was observed (p<0.01). Guided breathing showed a stronger treatment effect in terms of an increase in HRV, predominantly in low frequency band (p<0.03 vs. usual care). CONCLUSION: Even in well controlled hypertensive diabetic patients, guided breathing induced relevant effects on BP and HRV, finding which should be investigated further.

Modified orthostatic load for spectral analysis of short-term heart rate variability improves the sensitivity of autonomic dysfunction assessment.

AIM: To evaluate the impact of orthostatic load for sensitivity of short-term spectral analysis of heart rate variability (HRV) assessment of potential early autonomic dysfunction in diabetes mellitus. METHODS: Comparison of results of short-term time- and frequency-domain analysis of HRV during single positions and during modified orthostatic load (supine 1-standing-supine 2, each position 300 s) in diabetic subjects with good glycemic control (n=80, age 38+/-14, diabetes duration 16+/-10 years) and without autonomic neuropathy as assessed by a standard bedside reflex test battery, and in nondiabetic controls (n=150, age 40+/-13 years). RESULTS: None of the short-term frequency-domain parameters [absolute and logarithmic (LN) values of spectral powers in total- (TF), low- (LF), and high-frequency (HF) bands and its centroid frequencies] as obtained in single positions "supine" or "standing" revealed a significant difference between well-controlled patients and healthy controls (P>.3). However, during modified orthostatic load, significant differences in DeltaLN TF((supine 1-supine 2)) and in DeltaLN LF((supine 1-supine 2)) as well as in DeltaLN LF((standing-supine 2)) values between diabetic and healthy subjects were recorded [-0.2+/-0.5 vs. -0.1+/-0.4 LN (ms(2)), P=.05; -0.3+/-0.8 vs. 0.1+/-0.7 LN (ms(2)), P=.001 and 0.2+/-1.0 vs. 0.4+/-0.9 LN (ms(2)), P=.05, respectively] with insignificant intergroup differences in related centroid frequencies. This finding suggests a delayed recovery of LF spectral power in diabetic subjects after orthostatic challenge. CONCLUSIONS: When compared with single position measurements, the modified orthostatic load protocol improves the sensitivity of short-term HRV examination. In well-controlled diabetic subjects without cardiovascular autonomic neuropathy (as excluded by standard cardiovascular reflex testing), the delayed recovery of LF band spectral power after orthostatic load with standing up indicates diminished parasympathetic activation.

Functional assessment of heart rate variability: physiological basis and practical applications.

The autonomic nervous system dynamically controls the response of the body to a range of external and internal stimuli, providing physiological stability in the individual. With the progress of information technology, it is now possible to explore the functioning of this system reliably and non-invasively using comprehensive and functional analysis of heart rate variability. This method is already an established tool in cardiology research, and is increasingly being used for a range of clinical applications. This review describes the theoretical basis and practical applications for this emerging technique.