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Correlation of QT interval and heart rate variability in type 2 diabetic patients: Possible evidence for autonomic regulation of QT interval

Takeshi Arita, Taku Yokoyama, Shohei Moriyama, Mitsuhiro Fukata, Kei Irie, Toru Maruyama*, Takehiko Fujino & Koichi Akashi

Objective: QT interval length in Electrocardiogram (ECG) has prognostic impact on the patients with diabetes. This interval is influenced by autonomic nervous function, which is, however, impaired in diabetic patients. Since exact mechanisms of autonomic regulation of QT interval in diabetics remains unclear, this study aimed to investigate the relationship between heartrate- corrected QT interval (QTc interval) and Heart Rate Variability (HRV) in diabetic patients. Methods: Coefficient of variance of R-R intervals (CVRR:%) in digital ECG, as a representative time-domain measure of HRV, was estimated immediately after recording 12-lead ECG in type 2 diabetic (n=60) and nondiabetic control (n=62) groups. QTc interval was obtained by Bazett’s formula where QTc=QT/RR1/2. Demographic and laboratory data were extracted from medical records. Significant contributors of multiple clinical factors to the QTc interval length were analyzed by multivariate analysis. Results: Body mass index (p<0.001) and CVRR (p=0.015) contributed significantly to the QTc interval regulation in diabetic group, whereas CVRR (p=0.037) alone contributed significantly to this interval in controls. However, CVRR was correlated with the QTc interval negatively in diabetic group (standardized ÃŽ²=-0.306), whereas the opposite was found in the case of control group (standardized ÃŽ²=0.266). Conclusion: Although this allows a cross-sectional case-control study design, positive correlation of BMI and QTc interval in diabetic patients indicates cardiometabolic linkage (r=0.339, p=0.008). CVRR was considered to regulate QTc intervals. However, the details of this autonomic regulation in diabetics differed from those in controls. The mechanisms of autonomic QTc regulation in diabetics require future investigation.