Drug treatment of fetal tachycardias.

The pharmacological treatment of fetal tachycardia (FT) has been described in various publications. We present a study reviewing the necessity for treatment of FT, the regimens of drugs used in the last two decades and their mode of administration. The absence of reliable predictors of fetal hydrops (FH) has led most centers to initiate treatment as soon as the diagnosis of FT has been established, although a small minority advocate nonintervention. As the primary form of pharmacological intervention, oral maternal transplacental therapy is generally preferred. Digoxin is the most common drug used to treat FT; however, effectiveness remains a point of discussion. After digoxin, sotalol seems to be the most promising agent, specifically in atrial flutter and nonhydropic supraventricular tachycardia (SVT). Flecainide is a very effective drug in the treatment of fetal SVT, although concerns about possible pro-arrhythmic effects have limited its use. Amiodarone has been described favorably, but is frequently excluded due to its poor tolerability. Verapamil is contraindicated as it may increase mortality. Conclusions on other less frequently used drugs cannot be drawn. In severely hydropic fetuses and/or therapy-resistant FT, direct fetal therapy is sometimes initiated. To minimize the number of invasive procedures, fetal intramuscular or intraperitoneal injections that provide a more sustained release are preferred. Based on these data we propose a drug protocol of sotalol 160 mg twice daily orally, increased to a maximum of 480 mg daily. Whenever sinus rhythm is not achieved, the addition of digoxin 0.25 mg three times daily is recommended, increased to a maximum of 0.5 mg three times daily. Only in SVT complicated by FH, either maternal digoxin 1 to 2mg IV in 24 hours, and subsequently 0.5 to 1 mg/day IV, or flecainide 200 to 400 mg/day orally is proposed. Initiating direct fetal therapy may follow failure of transplacental therapy.