Longitudinal changes in QT interval variability and rate adaptation in pregnancies with normal and abnormal uterine perfusion.

The maternal heart significantly adapts to the circulatory needs of pregnancy, but the effect of pregnancy on ventricular repolarization is poorly understood. The aim of this study was to quantify longitudinal changes in ventricular repolarization during pregnancy. Monthly electrocardiographs (ECGs) were recorded in 32 pregnant women with normal uterine perfusion and 32 pregnant women with abnormal perfusion, starting from the 20th week of gestation until 3 days postpartum. Ventricular repolarization was assessed through various QT interval variability and heart rate adaptation measures. The pregnancy outcomes of all women with normal perfusion were normal. Among pregnancies with abnormal uterine perfusion, 15 pregnancy outcomes were normal, but 17 pregnancies developed preeclampsia and/or small-for-gestational-age infants. In pregnancies with normal perfusion, the QT(c) interval was unaltered, but the QT interval-heart rate hysteresis lag was shorter and the QT interval-heart rate regression residual was higher compared with those of a control group of 10 healthy non-pregnant women. Pregnancies with abnormal uterine perfusion that developed pathological outcomes showed significantly smaller QT interval-heart rate regression residuals and a trend towards shorter QT(c) intervals compared with pregnant women with normal perfusion. In conclusion, pregnancy has a significant effect on ventricular repolarization. Pregnancies with abnormal uterine perfusion and subsequent pathological outcomes are paralleled by changes in ventricular repolarization that precede clinical symptoms.