Surveillance and Treatment to Prevent Fetal Atrioventricular Block Likely to Occur Quickly (STOP BLOQ)

Condition(s) studied

Investigational drug(s) / intervention(s)

Dexamethasone: In mother in whom 2° AVB or AV interval \>170 ms has been diagnosed in the fetus: Dexamethasone 8 mg po/day for 10 days. Then dexamethasone 4 mg po/ day through 28 weeks 6 days gestational age (GA); then 3 mg/day from 29 wks 0 days to 29 wks 6 days GA; then 2 mg/day until delivery

IVIG: In a mother in whom 2° AVB has been diagnosed in the fetus: One dose of IVIG \[1g/kg of maternal weight (max dose 70 g)\] at diagnosis of 2° AVB (within 12 hours of detection by mother via home monitoring and within 6 hours of confirmation by echocardiogram). A fetal AV interval \> 170 ms will not be treated with maternal IVIG, only dexamethasone.

Study summary

Fetal complete (i.e., third degree, 3°) atrioventricular block (AVB), identified in the 2nd trimester of pregnancy in an otherwise normally developing heart, is almost universally associated with maternal anti-Ro autoantibodies and results in death in a fifth of cases. To date treatment of 3° AVB has been ineffective in restoring normal rhythm (NR) which may be because current surveillance is limited to once- weekly fetal echocardiograms. It is hypothesized that there may be a vital transition period of several hours in which incomplete block (2° AVB) may be successfully treated avoiding fully advanced irreversible 3° AVB. To optimize the likelihood of timely detection of the transition period this study comprises three steps: 1) to risk stratify for high titer anti-Ro antibodies, which are necessary but not sufficient to develop fetal AVB; 2) to empower mothers to identify 2° AVB by using fetal heart rate and rhythm monitoring (FHRM) at home, and 3) to rapidly treat mothers who detect an abnormality by monitoring with an urgent echocardiogram that confirms 2° AVB with the hope of reversing 2° AVB before it becomes permanent (3° AVB). In addition, it will be determined if FHRM reduces the need for weekly echoes. Although mothers with low titer anti-Ro will not be continued in Step 2 and therefore not followed by FHRM, birth ECGs will be collected to confirm that low titer antibodies do not confer risk. It is anticipated that this study will provide an evidenced based surveillance strategy for those mothers at high risk of having a child with 3° AVB.

Eligibility

Primary outcome measure(s)

• Percentage of 2° AVB subjects with NR (1:1 AV conduction) at birth — up to 25 weeks post-enrollment
  The presence of NR (normal rhythm) will be determined by electrocardiogram (ECG)

Trial sites (24)

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