Heart Rate and QT Interval in Streptozotocin-induced Diabetic Rat

Aim: Prolonged QT interval is a common finding in diabetic patients. The effects of streptozotocin (STZ) – induced diabetes on QT interval has been investigated by application of 4 standard QT correction algorithms. Methods: The electrocardiogram was recorded in STZ-treated (60 mg/kg bodyweight, ip) and agematched control rats with a biotelemetry system for the period of the study. Results: Heart rate (HR) was significantly (P<0.01) reduced and QT interval was signifycantly (P<0.05) prolonged in diabetic rats compared to controls at 8, 10 and 12 weeks after STZ treatment. At 8 weeks HR was 260±16 BPM (n=5) in diabetic rats compared to 333±25 BPM (n=5) in controls and QT interval was 70±7 ms (n=5) in diabetic rats compared to 59±6 ms (n=5) in controls. When QT interval was corrected for HR there was no longer any significant difference in QT interval between diabetic and control rats. The effects of different correction techniques have been compared and the consequences considered. Conclusion: The rapid and dramatic reductions in HR observed after administration of STZ are associated with a prolongation of the QT interval. However, the magnitude of the difference of the QT interval between the STZ and control groups was not significant after QT interval correction for the difference in HR.