ClinicalTrials.gg
Active, not recruitingNCT04474223Updated Aug 25, 2026

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

A Phase 3 interventional study of Dexamethasone and IVIG in AVB - Atrioventricular Block and Fetal AVB, sponsored by NYU Langone Health. Active, not recruiting at 24 sites in 2 countries. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-25.

Sponsored by NYU Langone Health · Phase 3, Interventional, and Treatment

Phase
Phase 3
Study type
Interventional
Enrollment
1,300
Allocation
Not applicable
Ages
18 Years and older
Sex
Female
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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.

Read the detailed description

Fetal complete (3°) atrioventricular block (AVB), identified in the 2nd trimester in an otherwise normally developing heart, is almost universally associated with maternal anti-Ro autoantibodies, which transcytose the placenta via the trophoblastic IgG receptor, FcγRn. The burden of 3° AVB is considerable: perinatal mortality of 18% exceeds that for all non-cardiac congenital anomalies combined, and almost all survivors require lifelong cardiac pacing with its associated complications. It has been speculated that full expression of conduction disease occurs by sequential fetal progression from normal rhythm (NR) to 1° AVB [prolonged AV interval assessed by echocardiogram (echo)], to 2° AVB (irregular cardiac rhythm or bradycardia), culminating in 3° AVB. Fetal heart rate and rhythm monitoring (FHRM) suggests a time interval of \~12 hours for the transition from NR to 3° AVB, albeit the culprit biologic processes (inflammation leading to fibrosis) likely initiate prior to clinical detection. Anecdotal evidence suggests this transition period, marked by an irregular rhythm and/or bradycardia, may be the only window of opportunity for anti-inflammatory treatment to restore NR.

A barrier to preventing progression to 3° AVB is the absence of a technique to accurately surveil for the precipitate transition from NR to 3° AVB. Surveillance limited to weekly echos (current standard of care) may be too infrequent to detect this transition period when treatment is most likely to be effective. We have now obviated this obstacle and shown that ambulatory FHRM by the mother at home with confirmation of abnormal findings by echo is not only feasible but may afford rapid treatment restoring NR. Combining results from studies comprising 275 anti-Ro+ pregnancies, 87% completed monitoring with a false positive rate of 5%. In 4 cases of 2° AVB identified by FHRM and treated \<12h, AVB reversed. Remarkably, no cases of 2° or 3° AVB were missed, suggesting mothers can recognize abnormal FHRM, reducing or precluding the need for weekly echos.

The proposed project combines the expertise of fetal cardiologist Bettina F. Cuneo, MD, initiator and PI of the FHRM program, and rheumatologist Jill P. Buyon, MD, founder/director of the largest extant registry of anti-Ro-mediated AVB, whose research on the pathogenesis supports a fetal inflammatory component associated with high-titer antibodies. Participants will be referred from 35 sites in 3 sequential Steps: 1) Screening for high titer anti-Ro60 or Ro52 centrally in Dr. Buyon's lab; 2) Surveillance by FHRM 3x daily and weekly echo; 3) Treatment of 2° AVB identified by FHRM confirmed by echo. Feasibility of FHRM supported by weekly echo of high-autoantibody-titer mothers will be leveraged to address the efficacy of expeditious (\<12 h after detection) treatment of 2° AVB as well as the incidence/outcome of AV interval prolongation and extra-nodal disease.

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Conditions studied

  • AVB - Atrioventricular Block
  • Fetal AVB
03

In context

Atrioventricular Block

117 studies on the registry are indexed under Atrioventricular Block; 43 are open to participants now.

This study's planned enrollment of 1,300 is above the median of 127 across 78 interventional studies indexed under Atrioventricular Block.

Browse Atrioventricular Block studies →

Lead sponsor

NYU Langone Health is the lead sponsor of 1,430 studies on the registry; 258 are open to participants now.

Of its 235 completed or terminated interventional studies of FDA-regulated products, 197 (84%) have results posted.

Counted across the registry records on this site, refreshed daily.

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Who can participate

Ages eligible
18 Years and older
Sexes eligible
Female
Accepts healthy volunteers
No

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  1. Provision of signed and dated form
  2. Stated willingness to comply with all study procedures and availability for the duration of the study
  3. Be \<18 weeks pregnant at the time of enrollment
  4. Titer of anti-Ro 52 or 60 antibodies ≥1,000 EU
  5. Any positive titer of anti-Ro if a history of a previously affected child
  6. Ability to take oral medication and be willing to adhere to the dexamethasone and IVIG protocols.
  7. Ability to perform Doppler fetal heart rate and rhythm monitoring in the ambulatory setting,
  8. Ability to send an audiotext message by cell phone therefore the participant will be informed that they need a phone with texting capabilities. Located within 6 hours drive of the participating pediatric cardiology site
  9. Be ≥18 years of age

Exclusion criteria

Exclusion Criteria:

  1. Multi-fetal pregnancy
  2. Known allergic reactions to components of IVIG, or dexamethasone or maternal IgA deficiency
  3. Fetal conduction system disease already present in the current pregnancy
  4. Any women who in the opinion of the investigator cannot understand the consent form or be able to perform thrice daily home monitoring or recognize an abnormal fetal heart rate or rhythm
  5. Women prisoners
  6. Treatment with >20 mg/prednisone q day or with any dose of fluorinated at enrollment
Terms in these criteria, in plain language(2)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Informed consent

Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.

You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.

Corticosteroids (steroids)

Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.

Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.

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Study design

Phase
Phase 3
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrollment
1,300 participants (estimated)

Study arms

  • Experimental
    Mothers with Fetuses Who Have 2° AVB or AV interval > 170ms

    Drug: Dexamethasone · Drug: IVIG

Interventions

  • 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

  • DrugIVIG

    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.

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What researchers measure

Primary outcomes

  1. Percentage of 2° AVB subjects with NR (1:1 AV conduction) at birth

    The presence of NR (normal rhythm) will be determined by electrocardiogram (ECG)

    Time frame: up to 25 weeks post-enrollment

Secondary outcomes

  1. Percentage of 2° AVB subjects who maintain NR at age 1 year.

    The presence of NR will be determined by ECG

    Time frame: 1 year post-birth

  2. Percentage of AV interval > 170 msec subjects with NR at birth

    AV intervals will be determined by EKG

    Time frame: At birth

  3. Incidences of isolated extra-nodal cardiac disease

    Extra-nodal cardiac disease includes: Endocardial fibroelastosis, dilated cardiomyopathy, and AV valve insufficiency. Isolated exta-nodal cardiac disease will be determined by echocardiogram.

    Time frame: up to 1 year post-birth

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Study locations

24 sites
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References and documents

Individual participant data

Plan to share: Yes — Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices) will be shared upon reasonable request.

Supporting information: Study protocol, Statistical analysis plan

Time frame: Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

Access criteria: The investigator who proposes to use the data will have access to the data upon reasonable request and when a stated purpose and approval by a committee is provided. Requests should be directed to Jill.Buyon@nyulangone.org. To gain access, data requestors will need to sign a data access agreement.

No publications or documents are linked to this record.

09

Timeline

Tracking since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reached

Started Aug 2020 (actual). Primary completion is estimated for Dec 2028, 100 months after the start.

How these figures are worked out, and which studies are left out of them.

Registered
Jul 14, 2020
First posted
Jul 16, 2020
StartActual
Aug 1, 2020
Primary completionEst.
Dec 31, 2028
CompletionEst.
Jun 30, 2029
Last update
Aug 25, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
No changes since tracking began. The registry record was last updated on Aug 25, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
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Registry details

Key details

Study ID
NCT04474223
Lead sponsor
NYU Langone Health
Responsible party
Sponsor
First posted
Jul 16, 2020
Start date
Aug 1, 2020
Primary completion
Dec 31, 2028 (estimated)
Completion
Jun 30, 2029 (estimated)
Last update
Aug 25, 2026

Study contacts

Jill Buyon, MD
principal investigator · NYU Langone Health
Bettina Cuneo, MD
principal investigator · University of Colorado, Denver

Oversight

Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is active, not recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.

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Studies of the drugs tested here: Dexamethasone · Immunoglobulins, Intravenous

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