Low penetrance, subclinical congenital LQTS: Concealed LQTS or silent LQTS?

Abstract

See article by Boulet et al. [1] (pages 466–474) in this issue . The paper by Boulet et al. in this issue [1] describes the electrophysiological basis of an ion channel malfunction reported in ‘a silent LQTS’ patient. This patient, a 40-year-old woman, had a documented syncopal event, palpitations, recurrent chest discomfort, tachycardia, and since diagnosis has been asymptomatic on β-blocker therapy [2]. Genetic analysis revealed a loss-of-function mutation in the KCNQ1 gene underlying the α subunit of the IKs potassium channel. It is important and interesting that this patient had a QTc interval of 430 ms, which is well within the normal range in women. Although there is no strict rule, QT prolongation is generally considered when the QTc interval is longer than 440 ms in men and 460 ms in women [3]. Therefore, the results of Boulet et al. demonstrated and discussed that a loss of function mutation in an important major potassium current (IKs) can result in torsades de pointes arrhythmia and syncope with normal QTc. The authors concluded that this mutation could be considered as a silent LQT1 syndrome, confirming the view regarding the important role of the IKs channel known to contribute to the repolarization reserve. This case and the underlying mechanism resemble well the previously described so-called subclinical congenital LQTS, concealed LQTS, and incomplete or low penetrance [4]. The … * Corresponding author. Email address: a.varro{at}phcol.szote.u-szeged.hu