Natural history of hydrops resolution in fetuses with tachyarrhythmias diagnosed and treated in utero.

Fetal tachyarrhythmias are life-threatening conditions for the fetus. Long-standing tachyarrhythmias often lead to fetal cardiac failure, hydrops and death. Normalization of the fetal cardiac rhythm leads to resolution of fetal hydrops. This report describes the sequence and timing of fetal hydrops resolution after successful therapy. Fetuses with a persistent heart rate over 180 beats/min with a 1:1 atrioventricular conduction (on M mode) were defined as having supraventricular tachycardia. Fetal hydrops was diagnosed if the following signs were seen: pleural and/or pericardial effusion and/or ascites or/and skin edema. Five fetuses with sustained fetal tachycardia and hydrops who converted to normal rhythm with antiarrhythmic agents treated at Stony Brook University Hospital and North Shore University Hospital between 1988 and 1995 are included. Resolution of hydrops required from 4 to 6 weeks and occurred in the following sequence: diminution of ascites; pleural and pericardial effusions, and disappearance of skin and scalp edema. Minimal signs of fluid retention (small ascites, mild hydrocele) remained in studied fetuses until term. Understanding the natural history of hydrops in cases of fetal tachyarrythmias will allow for accurate patient counseling pertaining to the expected timing of hydrops resolution after successful therapy.