Progressive involvement of cardiac conduction system in paediatric patients with Kearns–Sayre syndrome: how to predict occurrence of complete heart block and sudden cardiac death?

The aims of this study are to evaluate the progressive involvement of the cardiac conduction system in the Kearn–Sayre syndrome (KSS) and to establish criteria for the prevention of episodes of syncope or sudden cardiac death.

This is a prospective monocentric study including KSS patients, with diagnosis based on clinical manifestations, muscle biopsy, and genetic tests, before the age of 18. All patients underwent cardiac screening examination with 12-lead electrocardiogram (ECG), 24-h Holter monitoring, and pacemaker (PM) interrogation twice a year. Fifteen patients (nine males, mean age 16.6 ± 3.9 years) with a sporadic KSS were recruited. All subjects manifested at least one of the intraventricular conduction defects (IVDs): 1 right bundle branch block (RBBB), 2 left anterior fascicular block (LAFB), 11 a bi-fascicular block (RBBB + LAFB), and 1 left posterior fascicular block. Most children with bi-fascicular block developed LAFB before the RBBB (P = 0.0049). In six patients, IVD degenerated into atrioventricular block (AVB). Endocavitary PM was implanted in 11 patients (6 with AVB and 5 with a bi-fascicular block), while an implantable cardioverter-defibrillator only in one patient with a non-sustained ventricular tachycardia. Four died at mean age of 14.7 ± 2.6 years, but none of them suddenly.

Even a ‘simple’ ECG can predict the arrhythmic risk and the occurrence of catastrophic events in young patients with KSS. Left anterior fascicular block precedes RBBB in determining the bi-fascicular block and this can predict an inexorable progression of the conduction defects even in a short time. Pacemaker implantation may be indicated in these patients since the first bi-fascicular block manifestation.