Impact of Age and Gender on Mean QT and QTc Intervals Measured with Ambulatory Electrocardiogram Monitoring

Although the impact of age and gender on QT and QTc intervals on conventional electrocardiogram (ECG) has been well studied, the impact of these factors on mean QT and QTc intervals measured with ambulatory ECG monitoring has not been studied. The aim of this study was to assess the impact of age and gender on mean QT and QTc intervals measured with ambulatory ECG monitoring. Recordings of ambulatory ECG monitoring from 380 patients without significant cardiac abnormalities were analysed. The mean QT interval was longer in women (390.5 [373.0-405.0] ms) than in men (380.0 [366.0-397.5] ms) (p<0.001). The mean QTc interval was also longer in women (439.0 [429.0-447.5] ms) than in men (428.5 [417.0-441.0] ms) (p<0.001). The normal (2.5-97.5 percentiles) mean QTc interval measured with ambulatory ECG monitoring ranged from 393 to 466 ms in men and from 411 to 471 ms in women. QT and QTc intervals increased with age (p<0.001). There was a positive correlation between age and QT interval (r=0.474, p<0.001) as well as between age and QTc interval (r=0.263, p<0.001). Thus, female gender is associated with longer mean QT and QTc intervals measured with ambulatory ECG monitoring. QT and QTc intervals become longer with age.