Diagnosis and follow-up of fetal cardiac rhythm disturbances

Abnormal fetal heart rate patterns are detected in 0.2-2% of pregnancies and significant arrhythmias are present in the 10% of these cases. Fetal cardiac rhythm disturbances are classified in bradyarrhythmias, tachyarrhythmias and ectopic beats (or extrasystoles). The aim of this work is to describe the characteristics and the outcome of fetal cardiac rhythm disturbances. We considered 29 pregnancies complicated by fetal cardiac rhythm disturbances. Ectopic beats, the most frequent abnormalities, were detected in 65.5% of cases; not rarely extrasystoles were noted during echocardiographic evaluations until the end of pregnancy, however without any negative effect on fetal prognosis. In some cases fetal cardiac rhythm disturbances occurred also in postnatal life, usually with rhythm normalization during first months of life. Tachyarrhythmias were found in 24.1% of cases; in utero antiarrhythmic therapy was necessary in most cases, allowing fetal survival and the reaching of a gestational age adequate to avoid important consequences of prematurity. Antiarrhythmic therapy, administered to the mother with transplacental passage to the fetus, was effective in most cases. Sometimes, despite the control of arrhythmia in utero, the management of these cardiac rhythm disturbances was difficult because of postnatal relapses. The evolution of bradyarrhythmias, diagnosed in 10.4% of cases, has been similar to what usually described: in particular sinus bradycardia and bradycardia due to blocked atrial extrasystoles showed in utero resolution, whereas the complete atrioventricular block associated with left atrial isomerism had a poor prognosis.