Clinical Characteristics and Transplacental Treatment of Fetal Ventricular Tachycardia: A Nationwide Survey in Japan

BACKGROUND: Fetal ventricular tachycardia (VT) is an ultra-rare form of tachyarrhythmia, and no established management strategy currently exists. OBJECTIVES: This study aimed to clarify the current diagnostic and management approaches for fetal VT. METHODS: A nationwide survey of suspected fetal VT was conducted across 77 tertiary referral facilities in Japan between 2014 and 2023. RESULTS: In total, 24 fetal VT cases from 18 facilities were analyzed. Twenty cases were diagnosed based on atrioventricular dissociation. Four were initially diagnosed as supraventricular tachycardia. VT occurred by 32 6/7 weeks of gestation in all nine long QT syndrome (LQTS) cases (LQT 2 in six, LQT 3 in two, and other in one), whereas 8/15 non-LQTS cases occurred at term. Eight of 20 cases managed as fetal VT, and three of four cases managed as fetal supraventricular tachycardia received fetal treatment. Fetal treatments were effective in 9/11 cases overall and in 8/9 LQTS cases. Side effects were observed in 6/11 cases; however, no serious adverse events occurred, except one case of lidocaine toxicity. After birth, LQTS cases were more likely to be refractory to treatment than non-LQT cases (8/9 vs. 6/14), requiring multidisciplinary management. Neurodevelopmental delay was more frequent in LQTS cases than in non-LQTS cases (6/9 vs. 2/14). CONCLUSIONS: Transplacental treatment is highly recommended for preterm fetal VT. In particular, in cases of fetal VT diagnosed before 33 weeks of gestation, aggressive fetal treatment including magnesium sulfate and β-blockers should be considered with the possibility of LQT 2 or 3.