Changes in heart rate variability after modification of glucose lowering therapy in type 2 diabetic patients

Abstract

Background. The World Health Organization (WHO) has identified diabetes mellitus (DM) as a non-communicable epidemic of the XXI century. Cardiovascular pathology is a major cause of death for these patients. The purpose was to study the indicators of heart rate variability (HRV) in patients with type 2 DM, depending on the course of the disease, and HRV changes after the management of hyperglycemia. Materials and methods. We examined 53 type 2 DM patients and 10 healthy controls. Laboratory tests include determination of C-peptide, glycated hemoglobin (HbA1c), serum creatinine and urinary albumin concentration (UAC). All subjects underwent continuous glucose monitoring and 24-hour Holter monitoring at the same time. The patients were divided into 2 groups according to the НbА1с level: group 1 (n = 23) with НbА1с ≤ 7.0 % and group 2 (n = 30) with НbА1с > 7.0 %. The groups were divided into subgroups according to the absence (a) or presence (b) of hypoglycemia. The patients were re-examined after 6 months of glucose-lowering therapy modification. Results. HRV parameters did not differ significantly between the groups and subgroups of type 2 DM patients (p > 0.05). Both groups and subgroups, as well as the whole basic group of type 2 DM patient, had a significant decrease in SDNN daily, pNN50% daily, VLF daily, HF daily indicators compared with control subjects (р < 0.05). There were no statistically significant differences in daily TP between the control group and subgroup 1а only (р > 0.05). LF daily level was significantly lower compared to control only to all patients with type 2 DM. Daily LF/HF ratio was significantly higher in all subgroups of both groups than the control one (р < 0.05). Conclusions. Type 2 DM patients had significantly lower HRV, which mainly consists of SDNN, TP, VLF, HF LF/HF ratio. Six months after glucose-lowering therapy modification, we received a significant increase in most HRV indicators, except for LF. Main changes were observed in pNN50% daily (+50 %), pNN50% day (+50 %), RMSSD day (+43.5 %), RMSSD daily (+28.6 %), HF (+133.1 % – daily, +172.2 % — day, +57.5 % — at night) and a decrease in LF/HF ratio (–42.9 % — daily, –46.2 % — day, –32.7 % — at night) (p < 0.05). The results clearly demonstrate the restoration of the cardiac vagosympathetic balance due to compensation of carbohydrate metabolism.