Do components of metabolic syndrome contribute to cardiac autonomic neuropathy in non-diabetic patients?

OBJECTIVE: To evaluate whether autonomic dysfunction exist in patients with metabolic syndrome (MetS) to establish any association with components of MetS.

METHODS: From July 2008 to January 2009, 32 outpatients attending the University Clinical Center, Zemun, Belgrade, Serbia, 15 with MetS, 17 with type 2 diabetes mellitus (T2DM), and 15 control subjects were recruited for cross-sectional study among adults. The study was completed at the University Clinical Center, Bezanijska Kosa, and University Clinical Center, Dragisa Misovic, Belgrade, Serbia. Inclusion criteria were the presence of MetS without T2DM, T2DM and healthy controls, matched for age and gender. Exclusion criteria were uncontrolled diabetes (glycosylated hemoglobin [HbA1c] higher than 9%), advanced complications of diabetes (retinopathy, nephropathy, coronary heart disease, or peripheral angiopathy). Besides anthropometric and metabolic parameters cardiovascular autonomic reflex tests, ambulatory ECG monitoring, and blood pressure monitoring for 24 hours was obtained. Power spectral analysis of heart rate variability (HRV) was carried out by Fourier transformation.

RESULTS: Mean total power (TP) log-transformed (ln), very low frequency (VLF)ln power, and high frequency (HF)ln power were significantly lower in T2DM patients, when compared with controls, and only HFln power was significantly lower in the MetS group. The average value of low frequency (LF)/HFln ratio was significantly higher in T2DM and MetS, and significantly correlated with glucose level of the last one.

CONCLUSION: Disturbed HRV indices were present in patients with MetS before the development of T2DM. With this in mind, improvement of glucose metabolism, as well as early detection of cardiac autonomic dysfunction should be important.