The connection between QT dispersion and autonomic neuropathy in patients with type 2 diabetes

It is controversial whether an increase in the QT dispersion (QTd) on the electrocardiogram (ECG) reflects cardiac autonomic neuropathy in diabetic patients. In the current study, the QTd was compared in 60 type 2 diabetic patients and in 30 healthy subjects, and its association with autonomic neuropathy in diabetic patients was investigated. An increased QTd was found in diabetic patients, compared to healthy subjects. The QTd had significant negative associations with the log of the low and high frequency power (log LF and HF, respectively) of the power spectral analyses (PSA) of heart rate variations and the systolic blood response during standing (ABP). There was no significant difference in the QTd between patients with and without sympathetic skin response (SSR), reflecting peripheral sympathetic function. A significant positive correlation was also found between QTd and the systolic blood pressure (SBP). On the other hand, there was no correlation between QTd and serum total cholesterol (TC), triglycerides (TG), fasting plasma glucose (FPG), hemoglobin (Hb) A 1C concentrations or body mass index (BMI). By multiple regression analysis, the log HF, which reflects cardiac parasympathetic function, and the SBP alone were significantly associated with QTd as the dependent variable. The ΔBP and log LF, which partially reflect sympathetic nerve function, had no significant associations with QTd. These findings suggest that QTd reflects cardiac autonomic neuropathy (relative parasympathetic neuropathy) and that the QTd is also influenced by SBP, independent of autonomic neuro-function.