Characteristics and clinical interrelation of heart rate variability in patients with diabetic foot ulcers

Abstract

Objective Heart rate variability(HRV) was examined in hospitalized patients with diabetic foot ulcers(DFU) to investigate the characteristics and clinical interrelation of cardiovascular autonomic neuropathy(CAN). Methods A total of 115 patients with DFU treated in our hospital from January 2011 to December 2013 were included, and there were 59 males and 56 females with an average age of (68 ± 13) years. Another 109 individuals with high risk of DFU(Wagner 0 stage) were selected as the control group, and there were 74 males and 35 females with an average age of (65±14) years. HRV changes were analyzed in two groups, while subgroup analysis was done in DFU group according to Wagner classification. Furthermore, the patients with DFU were divided into two groups according to standard deviation of normal number of intervals(SDNN): patients with SDNN less than 70 ms were considered as HRV abnormal ones. Clinical indexes were compared among HRV abnormal and normal groups. The HRV parameters were tested in patients died in hospital and multi-regression model was used to analyze the association between clinical indexes and HRV parameters. The independence sample t test was implied in data comparison between two groups and variance analysis was used in data comparison among groups. Results The CAN of various degree existed in patients with DFU. Patients with abnormal HRV accounted for 51.3% of all the patients. Compared with those in controls, the incidence of peripheral neuropathy and peripheral vascular disease were significantly higher in the HRV abnormal group, which increased from 42.9% to 62.7% and 30.4% to 61.0%, respectively(χ2=4.547, 10.869, both P<0.05). Meanwhile, left ventricle ejection fraction was obviously decreased in the HRV abnormal group(61.9±6.5 vs 64.8±7.2,t= 2. 21,P<0.05). As the stage of Wagner elevated, the average heart rate increased in the DFU group(F=2.750, P<0.05), while SDNN, very low frequency (VLF) and low frequency to high frequency (LF/HF) ratio decreased significantly(F=2.275, 4.349, 3.084, all P<0.05). The VLF index, which reflects the tension of sympathetic nerve, largely decreased in dead patients when compared with that in the survivors(t=1.973,P< 0.05). Multiple regression analysis suggested that SDNN was negatively correlated with glycated hemoglobin A1c(HbA1c), 24-hour urine trace albumin (β=- 0.208, -0.214, both P<0.05), and the VLF index was also negatively correlated with HbA1c (β=-0.213,P<0. 05). Conclusion Patients with DFU are always complicated with CAN, and poor glycemic control is a significant cause of CAN. Thus, maintain the reasonable level of blood glucose along with combined therapy, is helpful to prevent the development of CAN in the long-term management of diabetic patients. Key words: Diabetic foot ulcers; Cardiovascular autonomic neuropathy; Heart rate variability