Abstract 2254: Prolongation of the Atrio-Ventricular Conduction in Fetuses Exposed to Maternal Anti-Ro/La Antibodies Does Not Predict Progressive Heart Block
Background: It has been suggested that congenital complete AV block (CAVB) related to maternal anti-Ro/La antibodies is preventable if detected and treated at an early stage of low-grade block. Consequently, steroids have been used to treat prolonged fetal AV conduction (AVC) ≥2 z-scores, consistent with 1st degree block (Friedman et al, Circulation 2008; Rein et al, Circulation 2009). We examined the prevalence and outcome of untreated 1st degree AV block.
Methods: Between 2003 and 2008, 132 fetuses of 114 anti-Ro/La antibody-positive women were enrolled in this prospective, single center study. Antibody-levels were confirmed by ELISA. Our protocol included serial evaluation of fetal AVC by ≥2 pulse-wave (PD) and tissue (TVI) Doppler modalities during the period at highest risk of progressive heart block and postnatal electrocardiograms. AV times were compared to institutional normal data.
Results: The 132 fetuses underwent 566 (2–12 exams/fetus) echocardiograms between 19 (17–23) and 24 (23–35) weeks. Of 120 cases with AVC <2 z-scores throughout the observation period, one was diagnosed with CAVB at 28 weeks, after the serial evaluation had ended. Of 10 fetuses with at least one AV interval measurement between 2–3 z-scores, none had postnatal AV block. Of 2 cases with persistent prenatal AV prolongation between 3.5–5.7 z-scores, only one had 1st degree block at birth. Thus, a fetal AV-duration between 2 and 6 z-scores was associated with a low positive predictive value (8%) to detect 1st degree block after birth and a 0% post test probability of CAVB. No other cardiac complications were detected.
Conclusion: Our results question the rationale of a management strategy that relies on the identification and treatment of AV prolongation to prevent CAVB. When it occurred, CAVB was not predicted and untreated 1st degree block did not progress.