Unusual electrocardiogram findings in a preterm infant after fetal tachycardia with hydrops fetalis treated with flecainide.

Fetal tachycardia and signs of hydrops fetalis were diagnosed at 29 weeks of gestation. The heart rate normalized by combined treatment with digoxin and flecainide and was followed by improvement of the hydrops. Premature labor led to delivery at 33 weeks of gestation. The newborn infant showed mild respiratory distress and was in a hemodynamically stable condition. Marked QT segment anomalies on the electrocardiogram during the first postnatal days resolved completely within 3 weeks. They were unlikely to be attributable to myocarditis or myocardial infarction. We speculate that these anomalies were caused by the maternal flecainide therapy.