Abstract
Prolongation of the heart-rate-adjusted QT interval (QTc) is prognostic of coronary heart disease, which is known to be associated with insulin resistance. Therefore, we studied the association of insulin resistance with QTc in 198 young healthy men (aged 18-20 years). QTc was positively associated with insulin (r=0.15, p=0.02) leptin (r=0.16, p=0.02), and both systolic and diastolic blood pressure (r= 0.18, p=0.009 and r=0.21, p=0.002, respectively). As compared with men in a median leptin tertile (1.5±0.2 [SD] ng/ml), those in a high tertile (4.2±4.2 ng/ml) had an increase in BMI (24.8±4.5 vs 20.7±1.6kg/m2), percent body fat (24.0±6.6 vs 17.1±2.9%) and QTc (391±23 vs 380±21 ms). In addition, mean QTc increased in a step-wise fashion from the lowest to the highest tertile of fasting insulin (378±22, 386±27, and 390±19 ms, respectively), a hallmark of insulin resistance, whereas mean QTc decreased in a step-wise fashion from the lowest to the top tertile of the ratio of fasting glucose to insulin (390±20, 386±25, and 379±23 ms), an estimate of insulin sensitivity in the nondiabetic population. In addition, mean QTc also decreased from the lowest to the top tertile of the insulin resistance index calculated using the homeostasis model assessment (381±22, 385±26, and 390±18 ms, p=0.06) These results suggest that QTc prolongation may be associated with insulin resistance.
