Fetal atrial flutter: diagnosis, clinical features, treatment, and outcome.

OBJECTIVES: To assess clinical features, treatment efficacy, and outcome of fetal atrial flutter. STUDY DESIGN: All atrial flutter cases seen in our unit between 1988 and 1995 were reviewed retrospectively and compared with the pooled data of 37 echocardiographically documented and published cases. RESULTS: Atrial flutter was found in 15 of 49 (30.6%) fetuses who had been referred because of clinically relevant tachyarrhythmia. Mean age at detection was 34+/-4 weeks' gestation. Atrial flutter was incessant in 11 and intermittent in 4, with a mean atrial rate of 442+/-65 beats/min and a mean ventricular rate of 216+/-28 beats/min. A predominance of 2:1 atrioventricular conduction was observed. In 5 of 15 cases another form of arrhythmia (supraventricular tachycardia, chaotic atrial rhythm, ventricular extrasystoles) coexisted with atrial flutter. Eleven fetuses were treated with maternal digoxin, and five subsequently converted to sinus rhythm. Four fetuses received no medication; of these four, two showed brief self-limited episodes of atrial flutter and two were delivered after detection of the arrhythmia. Only one fetus (6.7%), who did not respond to drug therapy, was delivered prematurely because of mild congestive heart failure. Seven neonates were in atrial flutter at birth; rhythm control could be easily achieved with sotalol or digoxin (n = 5), flecainide (n = 1), or electroconversion (n = 1) within the first 2 days of life without any relapse. CONCLUSION: Fetal atrial flutter accounts for approximately one third of all clinically relevant tachyarrhythmia. Although the suppression rate of incessant atrial flutter with digoxin is only 50%, this therapy may be useful for its positive inotropic and negative chronotropic properties. In our experience most fetuses with therapy-resistant atrial flutter and absence of 1:1 atrioventricular conduction do not experience congestive heart failure and do not need to be delivered prematurely. After birth, conversion to sinus rhythm was easily achieved in all neonates.