Parasympathetic versus sympathetic control of the cardiovascular system in young patients with type 1 diabetes mellitus

Autonomic neuropathy and cardiovascular dysregulation are common complications of the diabetes mellitus (DM). The aim of the study was to test the hypothesis that cardiovascular regulation is abnormal in young patients with type 1 DM. Patients with type 1 DM (17, 10 females, 7 males) aged 12.9-31.5 years (mean+/-SEM: 22.4+/-1.0 years) were investigated. The mean duration of DM was 12.4+/-1.2 years. The control group consisted of 17 healthy probands matched for sex and age. The length of R-R intervals was measured using telemetric system (VariaCardio TF4; Sima Media) where ECG signal (sampling frequency 1000 Hz) from thoracic belt was transferred into PC for further analysis. Systolic blood pressure (SBP) was monitored beat-to-beat using volume-clamp method by Finapres 2300 (Ohmeda). Spectral power in HF band of HRV (HRV-HF) was taken as an index of parasympathetic control and spectral power in LF band of systolic BPV (BPV-LF) as an index of sympathetic control. In young patients with type 1 DM significant reduction of spectral power in HF band of the heart rate variability was found, whereas no significant difference between DM group and control group was observed in spectral power in LF band of blood pressure variability. In conclusion, we found impaired parasympathetic control of heart rate in young patients with type 1 DM. No differences in blood vessels sympathetic control were detected using spectral analysis of BPV. We suggest that abnormalities in cardiac parasympathetic regulation precede impairment of blood vessels sympathetic control in young diabetics.