Relationship between QT interval and cardiovascular risk factors in healthy young subjects

The aim of this study was to evaluate the prevalence of a prolonged corrected QT interval (QTc) in a healthy young population and to investigate the association of QTc with cardiovascular risk factors. We examined 170 Caucasian subjects (aged 22–25, 84 males), evaluating height, weight, blood pressure, heart rate, fasting blood glucose and cholesterol, smoking habits and hypertensive familiarity. To determine QTc, a simultaneous 12-lead ECG was recorded by means of a 12-channel electrocardiograph (Mac 1200, Marquette Hellige Inc., Germany) at a paper speed of 50mm/s. QT interval (mean value of three calculated intervals) was corrected for the previous cardiac cycle length according to Bazett's formula. In both genders we evaluated the prevalence of a prolonged QTc (>440ms). Subjects were categorised in sex-specific tertiles of QTc; then we performed, separately in males and females, a multiple regression analysis to explain QTc (dependent variable, expressed in tertiles) as a function of the biological and environmental variables evaluated (body mass index, blood pressure, blood glucose and cholesterol, smoking habits, hypertensive familiarity). A prolonged QTc was observed in 10% of females and 5% of males (p for differences between sexes = 0.24). In a multiple regression analysis, QTc was positively associated with fasting blood glucose concentration in females (p=0.04) and systolic blood pressure in males (p=0.03). In conclusion, the significant positive relationship we found between QTc and blood glucose concentration (in females) or blood pressure (in males) suggests an association between potential cardiovascular risk factors and QTc duration, already present in young age and in subjects with QT interval, glycaemia and blood pressure values within the normal range.