Surveillance and Treatment to Prevent Fetal Atrioventricular Block Likely to Occur Quickly (STOP BLOQ)
Status:
Recruiting
Trial end date:
2026-01-01
Target enrollment:
Participant gender:
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.