title: Late potentials in a bradycardia-dependent long QT syndrome associated with sudden death during sleep.
abstract: The purpose of this study was to determine the incidence of late potentials and their relation to QT prolongation in a family with a high incidence of sudden death during sleep at a young age and bradycardia-dependent QT prolongation (n = 9) and to compare the findings with those in consanguineous family members without QT prolongation (n = 13). Six (67%) of the 9 family members with QT prolongation had late potentials on the signal-averaged electrocardiogram (ECG) compared with 1 of the 13 normal subjects (p less than 0.007). Positive predictive accuracy of the signal-averaged ECG for the detection of subjects with QT prolongation was 86%; negative predictive accuracy was 80%. During exercise testing, the QT interval normalized, whereas late potentials did not change significantly. Exercise testing did not reveal the presence of coronary artery disease as a possible cause of late potentials. It is concluded that 1) compared with family members with a normal QT interval, patients with this type of bradycardia-dependent QT prolongation have a high incidence of late potentials; 2) late potentials persist despite normalization of the QT interval at high heart rates, indicating that there is no direct relation between late potentials and QT prolongation; and 3) late potentials are not caused by coronary artery disease in these subjects. Therefore, the detection of late potentials might be a new aid in the detection and risk stratification of patients with the long QT syndrome. Late potentials possibly indicate a substrate for ventricular tachyarrhythmias in this type of bradycardia-dependent QT prolongation.
authors.affiliation: Department of Pharmacology/Clinical Pharmacology, University of Groningen, The Netherlands.
authors.forename: T J
authors.initials: TJ
authors.lastname: Tobé
authors.forename: C D
authors.initials: CD
authors.lastname: de Langen
authors.forename: M T
authors.initials: MT
authors.lastname: Bink-Boelkens
authors.forename: P H
authors.initials: PH
authors.lastname: Mook
authors.forename: J W
authors.initials: JW
authors.lastname: Viersma
authors.forename: K I
authors.initials: KI
authors.lastname: Lie
authors.forename: H
authors.initials: H
authors.lastname: Wesseling
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000175:diagnosis* / Q000209:etiology; D001919:Bradycardia / Q000150:complications* / Q000175:diagnosis; D002648:Child; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D004562:Electrocardiography / Q000379:methods; D005080:Exercise Test; D005190:Family; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012890:Sleep