Alteration in QT‐RR Relationship in Diabetic Patients with Autonomic Dysfunction

Background Impaired autonomic nervous activity and changes in ventricular repolarization might be related to catastrophic events in diabetic patients. Methods We analyzed the QT‐RR relationship and autonomic activity with Holter monitoring in 20 diabetic patients and 10 controls. The diabetic group was divided into two groups: 9 patients with normal coefficient of variance of RR interval (CV RR > 2.5%, DMN group) and 11 with low CV RR (CV RR ≤; 2.5%, DML group). Mean hourly QT and RR intervals were determined using the first 10 sinus beats of every hour. Spectral power of heart rate variability was determined with the fast Fourier transform technique. Results The DML group had shorter RR and QT intervals during sleep compared with the DMN group and control group. There was no difference in corrected QT interval among the three groups. The DML group showed decreased circadian variation of high‐frequency (HF) power, and steeper regression line and smaller correlation coefficient of QT‐RR relationship compared with other groups. There was an inverse correlation between InHF and the slope of the regression line of the QT‐RR relationship. Conclusions These results indicate that modulation of QT interval with heart rate is impaired along with impairment of cardiac parasympathetic activity in the DML group. Altered modulation of ventricular repolarization might contribute to the pathogenesis of catastrophic cardiac events in diabetic patients with neuropathy.