Concealed Long-QT Syndrome with Rare KCNQ1 Gene Mutation in an Elderly Female: A Case Report

Long QT syndrome (LQTS) is a hereditary disorder that can lead to recurrent syncope, convulsive episodes, and sudden death due to ventricular arrhythmia. In most instances, LQTS remains concealed and primarily presents as unexplained syncope despite have a normal electrocardiogram (ECG) during periods of rest. This characteristic can be highly deceptive and may result in severe and potentially fatal consequences if treated incorrectly. In this report, we present a case of concealed LQTS in an elderly female patient who experienced an initial episode of syncope at the age of 76. Upon admission, the surface ECG showed no abnormalities. However, during the bedside ECG examination, typical manifestations of LQTS were detected, indicating an early stage of the ictal process. Subsequent treatment with βblockers provided symptomatic relief. Genetic testing identified a rare mutation, p. Arg366Trp (with a c.1096C>T variant), in the KCNQ1 gene, confirming the diagnosis of LQTS. Although congenital LQTS cases are more commonly found in young females, the potential for LQTS should not be overlooked in elderly patients who complain of unexplained syncope, even if their ECG normal. The use of an artificial intelligence (AI)-based diagnostic tool has the potential to offer a more precise means of identifying concealed LQTS in the future, but, until now, thorough examination and close observation during admission is necessary to avoid missed diagnoses of the concealed LQTS-syndrome.