Which is responsible for cardiac autonomic dysfunction in non-diabetic patients with metabolic syndrome: Prediabetes or the syndrome itself?

AimsCardiac autonomic dysfunction (CAD) is associated with both prediabetes and metabolic syndrome (MS). Heart rate variability (HRV) and heart rate turbulence (HRT) are reliable 24-h Holter-ECG findings of cardiac autonomic function. This study aimed to investigate the relation between MS and its components and CAD using HRV and HRT.Materials and methodsThe study included 80 non-diabetic patients with MS and 70 control subjects. All study population and the patients with MS were further analyzed for each diagnostic component of MS to investigate which criteria impaired HRV and HRT.ResultsHRV and HRT parameters were disturbed in patients in the MS group. While impairment in HRV and HRT was significantly related to the presence of the fasting plasma glucose (FPG) criterion, there were no differences between groups in terms of the other 4 MS criteria. Moreover, FPG level was significantly correlated with SDNN (r = −0.352, p < 0.001), SDNN index (r = −0.423, p < 0.001), SDANN (r = −0.301, p < 0.001), RMSSD (r = −0.237, p < 0.001), pNN50 (r = −0.237, p < 0.001), turbulence onset (TO) (r = 0.365, p < 0.001) and turbulence slope (TS) (r = −0.365, p < 0.001). Among the MS diagnostic criteria, only FPG level was an independent determinant of all HRV and HRT parameters.ConclusionsThis study confirms the relation between MS and CAD. Increased FPG alone appears to be responsible for the mentioned findings among the 5 diagnostic criteria. Accordingly, CAD may be the result of prediabetes, not MS in patients with MS.