The maternal exposure of digoxin and flecainide in relation to the safety and effectiveness in the treatment of non-hydropic fetal tachycardia
Authors' conclusion
Digoxin monotherapy successfully treated fetal tachycardia in only 32% of cases. Adding flecainide improved response to 93%, although it increased side effects, which could be managed with dose reductions. Maternal digoxin levels were stable throughout pregnancy.
Study context
- Population
- Pregnant women treated for sustained non-hydropic fetal tachycardia, June 2007 to January 2023
- Participants
- 28 women
- Exposure
- Digoxin monotherapy, with added flecainide in non-responders
- Combinationn = 18
- Outcome
- Correlation between maternal drug exposure, effect and side effects
Main finding
As reported in the abstract
- Equal starting doses of digoxin gave similar maternal digoxin concentrations regardless of gestational age
- Maternal digoxin concentrations stable throughout pregnancy, little inter-patient variability
- Flecainide exposure varied within and between patients
- Responders vs Non-responders: P = 0.504
Observational data: associations, not effects.
Further findings
| Outcome | Monotherapy | Combination | P value |
|---|---|---|---|
| Conversion to sinus rhythm | 32% | — not stated in the abstract | |
| Fetus/mother digoxin ratio | median 0.51 (IQR 0.28–0.76) · n = 3 | median 0.45 (IQR 0.39–0.64) · n = 9 | P = 0.864 |
— not stated in the abstract
- Conversion to sinus rhythm — Total conversion rate with added flecainide
- 93% (26/28)
- Conversion to sinus rhythm: Monotherapy conversion after median 4.5 days (IQR 3-6.5)
Fetus/mother flecainide ratio
- Median fetus/mother flecainide ratio
- 0.82 (IQR 0.69-1.29)
Safety
- Side effects, primarily nausea, led to dose reductions; treatment remained effective
Original publication
The maternal exposure of digoxin and flecainide in relation to the safety and effectiveness in the treatment of non-hydropic fetal tachycardia. Heart Rhythm. Published 22 May 2025. doi:10.
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