Prediction of postnatal arrhythmia in fetuses with cardiac rhabdomyoma.

Fetal cardiac rhabdomyomas are rare but well-known to be associated with arrhythmia or conduction abnormalities. However, since in utero electrophysiological information is quite limited, it remains unclear which type of rhabdomyoma will develop arrhythmia after birth. The aim of this study is to identify factors that predict postnatal arrhythmia requiring therapy in fetuses with cardiac rhabdomyoma. A retrospective review of infants prenatally diagnosed with cardiac rhabdomyoma was performed at our tertiary pediatric cardiac center between 1990 and 2016. Fetal arrhythmia was diagnosed using fetal echocardiography and magnetocardiography. We compared the characteristics of cases with and without antiarrhythmic therapy after birth. Cases without antiarrhythmic therapy after birth consisted of those who had postnatal arrhythmia but did not require antiarrhythmic therapy and those who had no postnatal arrhythmia. A total of 20 fetuses with cardiac rhabdomyoma were included in this study. Ten cases (50%) were confirmed as having tuberous sclerosis after birth. The mean gestational week at diagnosis and delivery were 32.1 ± 2.7 and 37.6 ± 2.8 weeks, respectively. Mean cardiac tumor size in utero was 21 ± 11 mm (range, 7-54 mm) in diameter. Fetal arrhythmia was found in six cases; three resolved in utero with transplacental antiarrhythmic therapy. Postnatal arrhythmia or conduction abnormalities were found in 12 cases; 7 required antiarrhythmic therapy. Cases with antiarrhythmic therapy after birth had larger cardiac tumor in utero than those without therapy (29.6 ± 12.8 mm versus 16.3 ± 5.8 mm, p < .01). Cardiac tumor size >30 mm in diameter predicted postnatal arrhythmia requiring therapy with sensitivity of 57.1% and specificity of 100%. Location and number of cardiac tumor and presence of arrhythmia or conduction abnormalities in utero were similar between the two groups. Cardiac rhabdomyomas >30 mm in diameter are associated with postnatal arrhythmia requiring therapy regardless of number and location.