Perinatal outcome of fetal complete atrioventricular block: A multicenter experience

The clinical course and outcome of 55 fetuses with complete atrioventricular (AV) block detected prenatally were studied to identify factors that affect the natural history of this lesion. In 29 fetuses (53%) complete AV block was associated with complex structural heart defects, usually left atrial isomerism (n = 17) or discordant AV connection (n = 7). The other 26 fetuses had normal cardiac anatomy; in 19 cases the mother had connective tissue disease or tested positive for antinuclear antibodies. Six fetuses showed progression from sinus rhythm or second degree block to complete AV block. Of the 55 pregnancies, 5 were terminated and 24 fetuses or neonates died; at the end of the neonatal period 26 fetuses were still alive. Fetal or neonatal death correlated significantly with the presence of structural heart defects (4 of 29 surviving, p < 0.001), hydrops (0 of 22 surviving, p < 0.001), an atrial rate ≤120 beats/min (1 of 12 surviving, p < 0.005) or a ventricular rate ≤55 beats/min (3 of 21 surviving, p < 0.001). Mean atrial and ventricular rates were higher in surviving than in nonsurviving fetuses (142 ± 8 vs. 127 ± 21 beats/min, p < 0.002; 64 ± 8 vs. 52 ± 8 beats/min, p < 0.001, respectively). A slow atrial rate, however, was frequently associated with left atrial isomerism. In fetuses without left isomerism, mean atrial rate was not significantly different in surviving and nonsurviving fetuses (142 ± 8 vs. 144 ± 15 beats/min, p = 0.66), whereas ventricular rate remained different (64 ± 8 vs. 53 ± 8 beats/min, p < 0.001). In four cases, transplacental treatment by administering sympathomimetic drugs to the mother was attempted. Although ventricular rate increased variably, only one of these four fetuses, which had no additional structural defect, survived. Effective forms of fetal therapy are not established. A postnatal permanent pacemaker was implanted in 13 neonates; 9 survived the neonatal period.