The clinical significance of the irregular fetal heart rhythm

OBJECTIVE: Irregular fetal heart rhythms are common in clinical practice, but there is little information available on their significance or appropriate management. STUDY DESIGN: This was a retrospective review of fetuses seen during 10 years that either were referred for fetal echocardiography because of a fetal arrhythmia or were found incidentally to have an arrhythmia during fetal echocardiography for other indications. RESULTS: From 1988 through 1997 we performed 5566 fetal echocardiograms on 4838 different fetuses. There were 614 fetuses with irregular fetal heart rhythms. Among 595 referred for arrhythmias, extrasystoles were found in 255 (42.9%), normal rhythms were seen in 330 (55.4%), and hemodynamically significant arrhythmias were seen in 10. There were 2 fetuses with arrhythmias and structural heart disease. Nine of 10 fetuses with hemodynamically significant arrhythmias survived. An additional five neonates were found to have hemodynamically significant arrhythmias only postnatally. A total of 15 fetuses (2.4%) among those referred for irregular rhythms had significant arrhythmias. CONCLUSIONS: Irregular fetal heart rhythms signify hemodynamically significant arrhythmias in a small but important proportion of fetuses. Those without persistent irregularities on evaluation can be followed up with routine prenatal care.