Correlation of maternal flecainide concentrations and therapeutic effect in fetal supraventricular tachycardia.

BACKGROUND: Transplacental flecainide is an established therapy for fetal supraventricular tachycardia (SVT), but there is a paucity of data regarding the dose-response relationship. OBJECTIVE: The purpose of this study was to investigate the relationship between maternal flecainide concentrations, arrhythmia control, and adverse fetal effects in fetal SVT. METHODS: Fetuses with SVT treated with transplacental flecainide at our tertiary fetal cardiology unit between 1997 and 2012 were retrospectively studied. The maternal trough flecainide concentrations throughout treatment were collated, and clinical notes were reviewed to ascertain the response to therapy and fetal outcome. RESULTS: Thirty-three fetuses were treated at a median (range) gestation of 28 weeks (20-38 weeks). Median fetal heart rate was 250/min (range 207-316/min). One patient was lost to follow-up, and this fetus was excluded from further analysis. In total, 25 of 32 fetuses (78%) converted to sinus rhythm. Median time to conversion to sinus rhythm was 3 days (range 2-12 days). Median flecainide concentration was 460 µg/L (range 250-866 µg/L) at conversion to sinus rhythm. Flecainide concentrations were not significantly different between responders and nonresponders (P = .849). Twelve of 14 hydropic and 13 of 18 nonhydropic fetuses converted to sinus rhythm with similar flecainide concentrations (P = .316). No fetus achieved cardioversion with a maternal serum flecainide concentration <250 µg/L. No fetus died while being treated with flecainide. CONCLUSION: The clinical response to flecainide appears good, even in hydropic fetuses. Trough maternal flecainide concentrations, once therapeutic, do not predict cardioversion in the fetus with SVT. Flecainide therapy appears both safe and effective for the fetus when monitored appropriately.

Right aortic arch diagnosed antenatally: associations and outcome in 98 fetuses.

OBJECTIVE: To analyse the main characteristics, associated conditions and outcome of right aortic arch (RAA) detected in fetal life, and to assess if further investigation is required in cases of isolated RAA. METHODS: Retrospective observational study of all fetuses diagnosed with a RAA between 2004 and 2012 at a tertiary centre for fetal cardiology. RESULTS: A RAA was identified in 98 fetuses: 27 had normal intracardiac anatomy and 71 were associated with other congenital heart disease (CHD); conotruncal anomalies being the most common. An aberrant left subclavian artery was diagnosed in 18.4% of cases, a double aortic arch in 6.1%, and 12.2% had a vascular ring confirmed after birth. Overall, an extracardiac anomaly was present in 31.6% of the patients and a chromosomal anomaly in 15.3%, with half of the latter cases being 22q11.2 microdeletion. Extracardiac and chromosomal anomalies were more commonly associated with RAA with structural CHD (39.4% and 19.7%, respectively), compared to cases of RAA with normal intracardiac anatomy (11.1% and 3.7%, respectively) (p<0.05). First year mortality was 10.3%, with all deaths being in cases with associated structural CHD. CONCLUSIONS: Detailed fetal extracardiac examination should be undertaken in all cases of RAA. Isolated RAA has a good prognosis, and in the majority of the patients it is an asymptomatic vascular variant with a relatively low risk for chromosomal anomaly. The prognosis of RAA with CHD depends on the complexity of the CHD and/or the associated extracardiac anomalies. In these cases, there is a higher risk for chromosomal anomaly, particularly 22q11.2 microdeletion.