Abstract
Background: Increased aerobic capacity can reduce the incidence of cardiovascular disease and the mortality rate. On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of arrhythmias, cardiac sudden death and coronary artery disease.
Aims: The association of the aerobic capacity and coronary risk factors with QTc interval was investigated in postmenopausal overweight women.
Subjects and Methods: The subjects included 84 postmenopausal overweight women [age: 58.7±6.4 years, body mass index (BMI): 27.9±3.3] with coronary risk factors. Electrocardiogram (ECG) was recorded with a standard resting 12-lead ECG after more than 5 minutes of rest. The QTc interval was automatically calculated according to Bazett's formula. A multistage graded submaximal exercise test was performed on an electric bicycle ergometer to determine the estimated maximal oxygen uptake (VO2max).
Results: Single correlation analysis showed the QTc interval to be positively associated with hemoglobin A1c (HbA1c), fasting glucose, fasting insulin, BMI, waist circumference, serum potassium and the number of coronary risk factors, while negatively correlated with VO2max. Stepwise multiple regression analysis demonstrated the strong association of the QTc interval with HbA1c and VO2max (r2=0.244, p<0.0001). In both patients with and without metabolic syndrome (n=15, n=69, respectively), the QTc interval was independently associated with the HbA1c (r2=0.318, p<0.05, r2= 0.115, p<0.05, respectively).
Conclusions: These results suggest that decreased aerobic capacity and glucose intolerance may be independent risk factors for a prolonged QTc interval, while demonstrating no relationship with metabolic syndrome.
