Incipient cardiovascular autonomic imbalance revealed by wavelet analysis of heart rate variability in Type 2 diabetic patients.

AIM: Incipient cardiovascular autonomic imbalance is not readily diagnosed by conventional methods. Spectral analysis of heart rate variability (HRV) by wavelet transform (WT) was used to measure cardiovascular autonomic function in patients with Type 2 diabetes. METHODS: Thirty-two diabetic patients without (D), 26 with cardiovascular autonomic neuropathy (DAN) and 72 control subjects (C) participated. A 30-min HRV time series was analysed by wavelet transformation and four characteristic frequency intervals were defined: I (0.0095-0.021 Hz), II (0.021-0.052 Hz), III (0.052-0.145 Hz) and IV (0.145-0.6 Hz). RESULTS: When compared with C, in both D and DAN the normalized power and amplitude of interval II were increased and of interval IV decreased, resulting in a significantly higher II/IV ratio. Furthermore, in DAN the normalized power and amplitude of interval I were increased and of interval III decreased when compared with the D and C groups. The diabetic patients were divided in two equal subgroups according to HbA(1c) < 8.0% and >or= 8.0%. In the subgroup with HbA(1c) >or= 8.0%, normalized power in interval II was significantly higher and in interval IV significantly lower than in the subgroup with HbA(1c) < 8.0%. In D, but not in DAN patients prescribed ACE inhibitors, the absolute amplitude and power of oscillations were significantly higher than in patients not taking ACE inhibitor therapy. CONCLUSIONS: Patients with diabetes have increased sympathetic and decreased parasympathetic cardiac activity regardless of the presence of autonomic neuropathy. Glycaemic control and treatment with ACE inhibitors may favourably influence HRV in diabetic patients without autonomic neuropathy.

Skin blood flow in the upper and lower extremities of diabetic patients with and without autonomic neuropathy.

BACKGROUND: Microvascular blood flow in the human skin is subject to rhythmic variations reflecting the influence of heartbeat, respiration, intrinsic myogenic activity, neurogenic factors and endothelial activity. The aim of our study was to test the hypothesis that basal skin blood flow (BSBF) and its dynamic components differ (1) among diabetic patients without autonomic neuropathy and with it and healthy control subjects, and (2) among the upper and lower extremities. PATIENTS AND METHODS: BSBF at four recording sites with predominantly nutritive capillary circulation (right and left caput ulnae, right and left medial malleolus) was measured by laser Doppler flowmetry in 25 diabetic patients without cardiovascular autonomic neuropathy (D), 18 neuropathic diabetic patients (DAN) and 36 healthy controls (C). Wavelet transform was applied to the laser Doppler signal. RESULTS: In absolute terms, mean flow, mean amplitude of the total spectrum and mean amplitudes at all frequency intervals were highest in C, followed by DAN and lowest in D. However, these differences were statistically significant only in the left arm. Within all three groups, mean flow and spectral amplitudes were significantly higher in the arms than in the legs, besides there was a significant difference between the two arms in D. CONCLUSION: We have confirmed the differences in BSBF among D, DAN and C, and demonstrated differences among the four recording sites which have not been previously described. The latter indicates an uneven progression of autonomic neuropathy and allows for speculation that the left arm is the latest to be affected.