Characteristics
CHB is usually permanent and the clinical manifestations depend on the ventricular rate. Depending on the degree of scarring, the severity of conduction disorder may change: most affected fetuses retain their normal sinus rhythm, whereas some others show subclinical first-degree block or advanced block. CHB is an injury unique to some phases of development, because it has never been reported in the maternal heart despite the presence of identical antibodies in the maternal circulation. Even though the congenital heart block is irreversible, there are a few isolated cases in which AV nodal rhythm turns to sinus rhythm spontaneously. Only in one case it was reported that the AV node responded to exercise with accelerated heart rate although the patient had CHB . Low heart rate may result in fetal hydrops or neonatal heart failure. Some newborns can compensate with low heart rate, although most of them need pacemaker implantation