Newborn With Abnormal ECG and Family History of Sudden Cardiac Arrest.

Congenital long QT syndrome (LQTS) is a cardiac channelopathy caused by mutations in cardiac ion channel genes, leading to delayed ventricular repolarization, QT interval prolongation, and risk of malignant arrhythmias and sudden cardiac death. The condition often presents during childhood or adolescence but can be identified in neonates, particularly when there is a positive family history. Early recognition is critical, as timely intervention with beta-blockers and avoidance of QT-prolonging medications can prevent life-threatening events. We report the case of a full-term neonate born via cesarean section to a mother with congenital long QT syndrome (LQT2) and a strong family history of arrhythmic events. On day 1 of life, screening electrocardiogram (ECG) revealed a markedly prolonged corrected QT (QTc) prompting neonatal intensive care unit admission for further monitoring and evaluation. Propranolol was initiated, resulting in gradual QTc improvement over the first week of life. Genetic testing confirmed LQT2, with a pathogenic KCNH2 variant identified. The infant remained clinically stable and asymptomatic throughout hospitalization. The diagnosis of LQTS relies on a combination of ECG findings, clinical history, and genetic testing. Beta-blockers are the first-line therapy, and avoiding QT-prolonging medications is critical. In neonates, early recognition and treatment are vital to prevent arrhythmias. This case highlights the importance of early neonatal ECG screening in the setting of a family history of LQTS and emphasizes the need for multidisciplinary approach to optimize diagnosis, treatment, and counseling.