FETAL SUPRAVENTRICULAR TACHYCARDIA COMPLICATED BY HYDROPS-FETALIS - AROLE FOR DIRECT FETAL INTRAMUSCULAR THERAPY

Maternally administered digoxin for the treatment of fetal supraventri cular tachycardia (SVT) complicated by hydrops fetalis may be ineffect ive secondary to poor transplacental drug transfer. We present our exp erience with eight pregnancies treated with transplacental therapy or combined maternal and direct fetal intramuscular therapy. Response to treatment following maternal intravenous administration (MIV) of digox in or a combination of fetal intramuscular (FIM) digoxin and MIV is de scribed for eight hydropic fetuses during nine successful pharmacologi c conversions. The MlV digoxin was administered using standard loading and maintenance protocols. FIM was administered at a dose of 88 mu g/ kg q12-24 hours, to a maximum of three injections in the fetal buttock . Time to onset of the first two hours of sinus rhythm (TO2 degrees), time to onset > 90% sinus rhythm (TO > 90%), and time to resolution of hydrops fetalis (HF) were noted. The mean heart rate was 257 +/- 36 b eats/minute and the mean gestational age was 29 +/- 4.8 weeks. Fetal S VT was due to a reentrant mechanism in all cases. For the three fetuse s that underwent successful cardioversion following MIV digoxin (all r equired additional maternal antiarrhythmic drugs), TO2 degrees was 145 +/- 114 hours, TO > 90% was 176 +/- 55 hours, and HF resolved in 41 /- 37 days. Initial combined FIM and MIV therapy in four fetuses resul ted in a TO2 degrees of 5.5 +/- 4 hours, TO > 90% of 22 +/- 14 hours, and resolution of HF in 25 +/- 21 days. For the two failed cardioversi ons with transplacental treatment alone (one fetus had recurrent SVT w ith hydrops after initial successful cardioversion with MIV), TO2 degr ees was 203 +/- 180 hours and TO > 90% was 313 +/- 270 hours. Once FIM was begun in these two fetuses, TO2 degrees was 17 +/- 7 hours and TO > 90% was 60 +/- 13 hours; HF resolved in 45 days in one fetus, where as the other fetus never had resolution of hydrops despite 100 days of antiarrhythmic therapy. Direct fetal intramuscular injection of digox in combined with transplacental therapy appears to shorten the time to initial conversion of SVT and to sustain sinus rhythm in the fetus wi th SVT complicated by hydrops fetalis.