Prospective Identification of Long QT Syndrome in Fetal Life

Ascertainment of LQTS, an inherited arrhythmia disorder in a group of conditions known as the channelopathies, is challenging before birth. Recently, in a retrospective study it was reported that a gestational age dependent bradycardia allows a much higher recognition of genotype positive LQTS than the standard obstetrical gestational age independent definition of bradycardia (Mitchell 2012). However, the fetal heart rate in pregnancies with maternal or paternal LQTS diagnosed prior to the pregnancy has not been evaluated prospectively from the first trimester to birth. Nor is it known if the fetal heart rate /gestational age profile might be mutation specific. In addition, the use of fetal heart rate to successfully distinguish between LQTS and normal fetuses of pregnancies in which a parent has a known mutation has not been tested. The investigators believe that fetuses with an LQTS mutation born to families in which the mother or father has an LQTS mutation will have slower heart compared to fetuses, shown after birth not to have the family mutation. If the investigators hypothesis is correct, these findings could be applied to the general population of pregnant women to prospectively identify fetuses with LQTS and without a known family history. Since a fetal proband has been led to the identification of unsuspecting family members, prospectively identifying affected fetuses would increase ascertainment of life-threatening mutations in all ages (Cuneo 2013).