Clinical usefulness of corrected QT intervals in diabetic autonomic neuropathy in patients with type 2 diabetes

BACKGROUND: It is recognized that QTc intervals reflect autonomic nerve function. To investigate the clinical usefulness of corrected QT intervals (QTc) in assessing autonomic nerve function in type 2 diabetes, we measured QTc intervals using Bazett's formula in 58 type 2 diabetic patients and 20 age-matched healthy subjects. METHODS: We examined relationships between QTc intervals and the coefficient of variation of RR intervals (CV(RR)), systolic blood pressure response to standing, and sympathetic skin response (SSR) whose tests reflect autonomic nerve function. We also studied the correlation between QTc and blood pressure or serum lipid concentrations. RESULTS: QTc intervals in diabetic patients were significantly longer than those in healthy subjects and showed a significant but weak negative correlation with CV(RR), as well as systolic blood pressure response to standing. No significant difference in QTc intervals was observed between patients with and without a detectable SSR. QTc intervals showed a significant positive correlation with systolic and diastolic blood pressure although it did not correlate with serum lipid concentrations. QTc also tended to be long in obese diabetic subjects (body mass index > 25). CONCLUSION: QTc intervals might also be affected by other factors such as arteriosclerotic macroangiopathy and obesity, and not only autonomic nerve function. Therefore it might be considered as an overall index for complications, and not for pure autonomic impairment.