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Observational study of fetal heart rhythm issues

FAST Trial Registry: Prospective Observational Cohort Study of Fetal Atrial Flutter & Supraventricular Tachycardia

The Hospital for Sick Children · NCT03376438

This study is trying to see how different treatments for heart rhythm problems in unborn babies affect their health and the health of their mothers.

Quick facts

Study typeObservational
Enrollment400 (estimated)
Ages16 Years to 50 Years
SexFemale
SponsorThe Hospital for Sick Children (other)
Locations42 sites (Phoenix, Arizona and 41 other locations)
Trial IDNCT03376438 on ClinicalTrials.gov

What this trial studies

This study is a prospective observational cohort examining fetuses diagnosed with atrial flutter or supraventricular tachycardia severe enough to consider prenatal treatment. It aims to create a large clinical database to evaluate the efficacy and safety of various prenatal treatment strategies, including observation, transplacental antiarrhythmic treatment, and direct fetal treatment. The study will track outcomes from the time of diagnosis until either neonatal hospital discharge or a maximum of 30 days after birth, focusing on the health of both the mother and the fetus.

Who should consider this trial

Good fit: Ideal candidates include pregnant women with a singleton pregnancy and a fetus diagnosed with significant atrial flutter or supraventricular tachycardia.

Not a fit: Patients who are not pregnant or have multiple gestations may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could improve prenatal care and treatment strategies for fetuses with abnormal heart rhythms, potentially leading to better outcomes for both mothers and babies.

How similar studies have performed: While there is limited evidence on best practices for fetal tachyarrhythmias, this study aims to fill a significant knowledge gap, suggesting that similar studies have not yet established definitive treatment protocols.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

1. Mother has provided written informed consent to participate
2. Fetal AF or SVT with or without hydrops
3. Tachyarrhythmia that is significant enough to justify immediate transplacental pharmacological treatment:

   * Tachycardia ≥ 180 bpm during at least 10% of observation time of 30 minutes or longer
   * Tachycardia ≥ 170 bpm during +100% of time (≤ 30 0/7 weeks of gestation)
   * Tachycardia ≥ 280 bpm (irrespective of SVA duration)
   * SVT with fetal hydrops (irrespective of duration)
4. Gestational age \<36 0/7 weeks at time of enrollment
5. Singleton Pregnancy
6. Healthy mother with ± normal pre-treatment cardiovascular findings:

   * ECG within normal range (sinus rhythm; QTc ≤ 0.47; PR ≤ 0.2 sec; QRS: ≤ 0.12 sec; insignificant anomalies; isolated premature beats; isolated complete right bundle
   * Maternal resting heart rate ≥ 50 bpm
   * Maternal systolic BP ≥ 85 mmHg

Exclusion Criteria:

1. Primary delivery for postnatal cardioversion
2. Antiarrhythmic fetal treatment for more than 2 days at time of enrollment
3. Any maternal-fetal conditions associated with high odds of premature delivery and/or death
4. History of significant maternal heart condition (open heart surgery; sick sinus syndrome; long QT, Brugada syndrome; ventricular tachycardia; WPW syndrome; high-degree heart block; cardiomyopathy)

Where this trial is running

Phoenix, Arizona and 41 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Atrial Flutter, Tachycardia, Supraventricular, Tachycardia, Atrial Ectopic, Tachycardia, Reciprocating, Tachycardia Atrial, Tachycardia, Atrioventricular Nodal Reentry, Tachycardia, Paroxysmal, Fetal Hydrops

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.