Diagnosis of a Neonate With Long QT Syndrome and Severe Complications Delayed due to an Unrecognized Familial History

Long QT syndrome (LQTS) is a hereditary arrhythmic disorder associated with sudden cardiac death. We report a neonatal case of congenital LQTS that went undiagnosed in utero, leading to severe postnatal complications. A male preterm infant was delivered by emergency cesarean section due to fetal hydrops. Shortly after birth, he developed respiratory failure and metabolic acidosis, followed by ventricular tachycardia and torsades de pointes requiring prolonged resuscitation. During cardiopulmonary resuscitation, the father collapsed, and it was subsequently established that he had been receiving treatment for LQTS. The paternal grandmother also had the same diagnosis. Genetic testing performed for the infant identified a pathogenic KCNH2 variant (c.1714G > A, p.Gly572Ser), confirming Type 2 LQTS. Despite antiarrhythmic therapy and ventricular pacing, the patient developed severe intraventricular hemorrhage and hydrocephalus. This case serves to emphasize the importance of obtaining a detailed family history and the need for effective communication among obstetricians, neonatologists, and cardiologists. In this instance, a lack of awareness regarding familial LQTS contributed to a delay in diagnosis and intervention. Our findings highlight the essential roles played by early detection and prenatal risk assessment through family screening and genetic testing for preventing life‐threatening arrhythmia and improving outcomes in congenital LQTS.