A baby was born through emergency C-sec delivery at 28+3 weeks of gestation, with a birth weight of 1.3 kg, due to fetal ventricular tachycardia, severe ventricular dysfunction, and fetal hydrops (Figure 1, Supplementary Videos 1 and 2).1) Electrocardiogram and Holter monitoring showed intermittent 2:1 atrioventricular blocks (AVB) and prolonged QT interval with a circulatory collapse during bradycardia (Figure 2). Inotropes including isoproterenol were started, but bradycardia episodes persisted despite decrease in frequency. After a week of unstable clinical conditions, ventricular functions began to improve and the patient began to tolerate bradycardia episodes due to 2:1 AVB. At a month of age, a non-sustained polymorphic ventricular tachycardia (Torsades de Pointes; TdP) developed, 2–3 times a day (Figure 3). A beta-blocker was applied without an effect, then oral mexiletine was added, resulting in a gradual decrease of QT interval and the AVB episodes, and eventually TdP disappeared (Figure 4). The patient was discharged home at 87 days after birth, taking propranolol and mexiletine. Currently, the patient is 16 months old and in normal growth without any cardiovascular event. The last electrocardiogram showed 1:1 AV conduction with much decreased QTc (470 ms) (Figures 4 and 5). Next-generation sequencing revealed a KCNH2 gene mutation and long QT syndrome (LQTS) type 2 was confirmed.
Ventricular arrhythmia and/or 2:1 AVB associated with LQTS may cause fetal hydrops and intrauterine fetal demise, have been reported to have high mortality rate during infancy, and frequently need device therapy.2)3) Mexiletine may be a good alternative choice for these patients.4)5)
The Institutional Review Board of Seoul St. Mary's Hospital approved this study and the informed consent was waived (IRB number: KC21ZISI0437).
Notes
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
Presentation: The case has been presented at the 64th Annual Scientific Meeting of the Korean Society of Cardiology in 2020.
References
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