Objective: Cardiac autonomic nervous dysfunction (CAND), a severe complication of diabetes, has also been shown to affect prediabetic patients. The role of isolated impaired fasting plasma glucose (IFG), a subtype of prediabetes, is not clear in the pathogenesis of CAND. The aim of this study was to examine the relationship between isolated IFG and cardiac autonomic function using heart rate variability (HRV) and heart rate turbulence (HRT) indices derived from 24-h Holterelectrocardiogram recordings.
Methods: This observational, prospective, cross-sectional study examined 400 consecutive subjects divided into three groups according to oral glucose tolerance test results: the control group [Group I, fasting plasma glucose (FPG) <100 mg/dL and normal glucose tolerance, n=193], the isolated IFG group (Group II, FPG ≥100 and <126 mg/dL, n=134), and the isolated impaired glucose tolerance (IGT), both IFG and IGT, or newly diagnosed diabetes group (Group III, n=73). Patients with non-sinus rhythm, known diabetes mellitus, coronary artery disease, heart failure, severe valvular disease, or receiving medical therapy that may affect HRV and HRT indices were excluded. Time domain HRV parameters, turbulence onset (TO), turbulence slope (TS), and HRT category were examined. Chi-square, one-way analysis of variance, KruskalWallis H, and MannWhitney U tests were used to compare variables where appropriate. The correlation between Holter data and FPG levels was analyzed using the Spearmans test. Multiple linear regression analysis was performed to identify independent predictors of the HRV and HRT parameters.
Results: Median (interquartile range 2575) FPG levels in Groups I, II, and III were 89 (83/93) mg/dL, 109 (104/116) mg/dL, and 174 (150.5/197) mg/dL, respectively. There were significant differences in HRV and HRT parameters between and among all groups. While HRV parameters and TS decreased from Group I to Group III, TO and HRT category gradually increased. Additionally, FPG level was significantly correlated with SDNN, r=0.220; SDNN index, r=0.192; SDANN, r=0.207; RMSSD, r=0.228; pNN50, r=0.226; TO, r=0.354; and TS, r=0.331 (all p<0.001).
Conclusion: CAND, as detected by both HRV and HRT, appear to be present in the isolated IFG subtype of prediabetes. (Anatol J Cardiol 2016; 16: 762-9)