Fetal tachyarrhythmias: current knowledge for clinical practice

Fetal arrhythmias account for 10-20% of all outpatient consultations in specialized fetal medicine centers. Furthermore, it is evident that tachyarrhythmias account for 8% of all such arrhythmias. Most arrhythmias are benign and easy to manage, but certain tachyarrhythmias require close monitoring due to the risk of decompensation, progression to heart failure with hydrops, and potential fetal death. The aim of this study was to describe the most common fetal tachycardias and their intrauterine management. Using fetal ultrasound/echocardiography, clinicians can assess the heart rate (HR), fetal heart rhythm, and determine rhythm patterns. Differentiating the type of fetal tachyarrhythmia is crucial, as certain antiarrhythmic drugs are more effective for specific arrhythmias. Despite advances in diagnosis and treatment, studies reveal limited numbers of patients, and a wide variety of treatments based on local experience and available resources. The potential of fetal treatment to improve prognosis in both fetal and postnatal life has been well demonstrated. There are several treatment options for fetal tachyarrhythmias, with the most effective medication selected based on the healthcare team's experience and practical treatment considerations. Transplacental therapy is the most widely used route for administering antiarrhythmic drugs in utero. In general, studies have been demonstrated the superior efficacy of flecainide and sotalol in comparison to digoxin in the treatment of fetal supraventricular tachycardia (SVT), with or without fetal edema. Flecainide can be used in combination with digoxin to treat SVT and hydrops in fetuses. For sustained ventricular tachycardia (VT), first-line treatment is maternal intravenous magnesium when fetal HR exceeds 200 bpm. In addition, it is important to keep in mind that frequency control is the treatment option for fetuses in which reversal to sinus rhythm has not been successful and pulmonary immaturity is present.