The beginnings of long QT syndrome

PURPOSE OF REVIEW: The purpose of this study is to update the perinatal cardiologist and obstetrical care provider on the presentation and management of the fetus with long QT syndrome (LQTS). RECENT FINDINGS: LQTS is a known cause of sudden death in childhood, adolescence and young adulthood that presents during fetal life, but is often not recognized. Torsades de pointes (TdP) ±2° atrioventricular block (AVB) are not always attributed to LQTS, although the most common LQTS rhythm, a fetal heart rate of less than third percentile for gestational age (GA), is not recognized as abnormal because it does not meet the standard obstetrical criteria for bradycardia. Early recognition and appropriate treatment can be life saving for the fetus and unsuspecting LQTS family members. Fetal rhythm phenotype and postnatal QTc can predict postnatal rhythm and suggest genotype: bradycardic fetuses usually have KCNQ1 mutation, while those with TdP and/or a postnatal QTc more than 500 ms have SCN5A, KCNH2 or uncharacterized mutations. SUMMARY: The fetus with repeated heart rates of less than third percentile of GA and those with TdP ±2° AVB are likely to manifest the same rhythm after birth and have an LQTS mutation.