Evolving therapies for fetal supraventricular tachycardia: Precision pharmacology, hydrops rescue, and emerging interventions – A systematic review and illustrative case series

Abstract: Fetal supraventricular tachycardia (SVT) remains one of the most challenging rhythm disturbances encountered in perinatal practice, particularly when sustained tachycardia progresses to hydrops fetalis. Despite decades of therapeutic experience, substantial variation persists in drug selection, escalation strategies, and the use of invasive fetal rescue techniques. To clarify contemporary evidence and delineate emerging therapeutic directions, we conducted a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, examining studies published across major databases and registers, with 33 studies meeting full eligibility criteria and 20 forming the core analytic evidence base. The literature reveals a steady shift from traditional digoxin-first approaches to precision-oriented pharmacology, supported by multicenter data demonstrating higher conversion rates with flecainide and sotalol, especially in hydropic or high-rate SVT. Hydrops remains the principal marker of treatment failure and is associated with longer time to conversion, prompting increased use of combination therapy and carefully monitored maternal dosing strategies. Although reserved for refractory disease, direct fetal interventions – such as umbilical venous administration of antiarrhythmics or drainage of large effusions – have re-emerged as lifesaving options in select cases. Recent work highlights the role of maternal–fetal pharmacokinetic monitoring, computational rhythm analysis, and genetic evaluation for channelopathies in refining clinical decision-making. Four illustrative clinical vignettes integrate these evolving concepts and demonstrate how tailored therapy can alter the trajectory of severe cases. Overall, the evidence indicates a transition toward individualized, physiology-guided care, while simultaneously underscoring persistent gaps in comparative effectiveness research, standardized monitoring strategies, and long-term developmental outcomes. Continued interdisciplinary collaboration will be essential to advance fetal SVT therapy into a more predictable and precise era.