The most common cardiac feature of
Kearns-Sayre syndrome (KSS) is
atrioventricular block (AVB), and pacemaker implantations (PMIs) are recommended for KSS patients with advanced AVB. However, some KSS patients develop fatal arrhythmias such as polymorphic
ventricular tachycardia (PMVT) and
ventricular fibrillation (VF) and die suddenly even after PMIs. We report a patient with KSS who developed PMVT, VF, and QT prolongation, and was treated with
mexiletine and successfully managed with an
implantable cardioverter defibrillator (ICD). We reviewed the literature on arrhythmias in KSS published from 1975 to 2018. There were 112 patients with
arrhythmia-associated KSS, 10 died, and 6 died suddenly after the PMI. The first manifestation of an
arrhythmia was
bundle branch block, then it progressed to AVB, and developed into complete AVB (CAVB) in about half the KSS patients. Ventricular arrhythmias were documented in 12 patients, and 8 were implanted with
defibrillators afterwards. One patient after the implantation of a
cardiac resynchronization therapy defibrillator (CRT-D) was treated for VF by an appropriate
shock. This fact suggested that VF occurred even under proper pacing, and that
defibrillators were effective. Pacemakers may suppress early afterdepolarizations (EADs) associated with a QT prolongation due to
bradycardia. Similarly,
mexiletine may suppress EADs by blocking the late
sodium and Ca currents. Ventricular arrhythmias observed under suppression of EADs may be caused by delayed afterdepolarization (DADs) via an increasing intracellular Ca concentration due to
mitochondrial dysfunction. Therefore, a PMI alone may not be sufficient to prevent
sudden death, and an ICD implantation should be necessary.