Fetal presentation of long QT syndrome--evaluation of prenatal risk factors: a systematic review.

OBJECTIVE This systematic review evaluated the existence of risk factors for the fetal manifestation of long QT syndrome (LQTS). METHODS Prenatal cardiac findings suggestive of fetal LQTS were studied using 30 English literature reports extracted from the Pubmed database (1979 to December 2011) using the search terms 'long QT syndrome', 'fetal arrhythmia' and 'congenital heart disease'. RESULTS LQTS accounted for 15-17% of fetal bradycardias <110 bpm among fetuses with a normally structured heart. Of the patients with significant prenatal findings of LQTS, 17-35% exhibited a reduced baseline fetal heart rate (FHR) of 110-120 bpm on electronic cardiotocography. Other prenatal signs were sinus or intermittent bradycardia <110 bpm arising from atrioventricular block, tachyarrhythmias, pleural effusion and hydrops. More than 30% of Japanese infants with LQTS born at or after the mid-1980s exhibited the above-mentioned in utero signs. CONCLUSIONS Fetal factors including a slightly reduced baseline FHR of 110-120 bpm, bradycardia <110 bpm, tachyarrhythmias or clinical signs of heart failure, such as pleural effusion and hydrops, were associated with a higher frequency of LQTS. The use of these signs may help to increase the perinatal diagnosis of LQTS.