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Abstract：
Background: Early diagnosis of long QT type 3 (LQT3) syndrome during the neonatal period is of paramount clinical importance. LQT3 syndrome results in increased mortality and a mutation-specific response to treatment compared to other more common types of LQT syndrome. Mexiletine, a sodium channel blocker, demonstrates a mutation-specific QTc shortening effect in LQT3 syndrome patients. Case Presentation: A neonate manifested marked QTc prolongation after birth. An electrocardiogram (ECG) recording was performed due to positive family history of genetically confirmed LQT3 syndrome (SCN5A gene missense mutation Tyr1795Cys), and an association with sudden cardiac death was found in family members. The mexiletine QTc normalizing effect (QTc shortening from 537 to 443 ms), practical issues related to oral mexiletine treatment of our young patient, along with a literature review regarding identification and mexiletine treatment in infants with LQT3 syndrome are presented. Conclusions: Mexiletine could be considered in the treatment of high-risk LQT3 patients already in the neonatal period in addition to b-blocker therapy. Availability of standardized commercial mexiletine pediatric formulas, serum mexiletine level analyses, and future prospective studies are needed to evaluate the potential beneficial effect of early mexiletine treatment on the incidence of future acute cardiac events in these high-risk LQT syndrome patients.
摘要：
背景：在新生儿期早期诊断长QT3型（LQT3）综合征至关重要。与其他更常见类型的LQT综合征相比，LQT3综合征导致死亡率增加和对治疗的突变特异性反应。美西律,钠通道阻滞剂,证明了LQT3综合征患者的突变特异性QTc缩短效应。病例介绍：一名新生儿出生后表现出明显的QTc延长。由于基因证实的LQT3综合征（SCN5A基因错义突变Tyr1795Cys）的阳性家族史，进行了心电图（ECG）记录，在家庭成员中发现与心源性猝死有关。美西律QTc正常化效应（QTc从537缩短至443ms），与我们年轻患者口服美西律治疗有关的实际问题，本文还介绍了有关LQT3综合征婴儿的识别和美西律治疗的文献综述。结论：除了b受体阻滞剂治疗外，美西律可用于治疗新生儿期的高危LQT3患者。标准化商业美西律儿科配方的可用性，血清美西律水平分析，未来的前瞻性研究需要评估早期美西律治疗对这些高危LQT综合征患者未来急性心脏事件发生率的潜在有益作用.
