Anti-Ro52/SSA antibody-exposed fetuses with prolonged atrioventricular time intervals show signs of decreased cardiac performance.

OBJECTIVE: To investigate if anti-Ro/SSA antibody-exposed fetuses with prolonged atrioventricular (AV) time intervals also have prolongation of the isovolumetric contraction time (ICT).

METHODS: Seventy-eight anti-Ro/SSA (including 70 anti-Ro52) antibody-exposed fetuses at risk for congenital heart block (CHB) were followed weekly, between 18 and 24 weeks of gestation, with two Doppler echocardiographic methods designed to detect signs of first-degree AV block. One of these AV time measurements, using hemodynamic events from the mitral valve and aortic outflow as indirect markers of atrial and ventricular depolarization (MV-Ao), was also used to calculate a time interval representing an early phase of systolic cardiac performance, i.e. the ICT. Two hundred and eighty-four women with normal pregnancies served as controls for AV time intervals and another 106 were used to establish an ICT reference range.

RESULTS: Strong positive relationships were found between ICT and MV-Ao time intervals (r = 0.91, P < 0.001), as well as between ICT and time intervals obtained from the superior vena cava and aorta (r = 0.85, P < 0.001). The ICT was estimated to contribute more than 50% of the total AV time prolongation. Abnormal AV time and ICT intervals were only seen in anti-Ro52 positive pregnancies.

CONCLUSIONS: The ICT is an important contributor to prolongation of AV time intervals. This observation suggests that anti-Ro52/SSA antibody-exposed fetal hearts have not only disturbed electrical conduction but also decreased mechanical performance. Moreover, our findings have implications for the interpretation of AV time intervals used for surveillance of fetuses at risk for developing CHB.