Amiodarone and fetal supraventricular tachycardia. Apropos of a case with neonatal hypothyroidism]

BACKGROUND. Fetal tachycardia can be a cause of in utero death. Its detection is not always easy and its treatment is still controversial. CASE REPORT. Paroxysms of supraventricular tachycardia were detected on echocardiography at the 25th week of a second pregnancy. The mother was given sotalol, but the supraventricular tachycardia became permanent. At the 27th week of gestation, sotalol was stopped and the mother was given digoxin and the foetus received 2 injections of digoxin, 10 micrograms/kg, via the umbilical cord. As this treatment was only partially effective, the mother was also given amiodarone 800 mg/day at week 28, then the dose was reduced to 400 mg/day. However, at the 31st week, the mother showed signs of digoxin intolerance, and it was replaced by sotalol. Fetal blood tests at week 34 showed a high placental transfer of digoxin and sotalol and a low fetal level of amiodarone. The newborn, a girl, was born at the 36th week having a sinus rhythm. She developed signs of hypothyroidism (T4: 4 micrograms/ml; TSH:325 microliters U/ml at 5 days of life). CONCLUSION. The placental transfers of sotalol, digoxin and amiodarone are in the range of values known to be effective. The amiodarone responsible for hypothyroidism was given to the mother because she was intolerant to digoxin. Its use must be limited to arrhythmias that are resistant to other drugs or complicated by hydrops fetalis. When used, amiodarone should not be given for more than 6 weeks, and at the lowest possible dose.