A Slower Heart Rate and Therapeutic Hypothermia Unmasked Early Repolarization Syndrome in a Ventricular Fibrillation Survivor

Efficacy of a Subcutaneous Implantable Cardioverter Defibrillator in a Child with Early Repolarization Syndrome

An early repolarization (ER) pattern or J waves are considered to be a benign finding observed in the healthy population, however, it has been pointed out that the ER pattern seen in the inferolateral leads could be an independent risk factor for fatal arrhythmias. We present a pediatric case in which early repolarization syndrome (ERS) was suspected due to the presence of ER or J waves in the inferior leads, which eventually disappeared after the administration of pilsicainide. During the follow-up period, several fatal ventricular arrhythmias were recorded after implantation of a subcutaneous implantable cardiac defibrillator (S-ICD). This report describes the efficacy of S-ICDs in a child with an ER pattern after aborted sudden cardiac death.

Novel Cardiocerebral Channelopathy Associated with a KCND3 V392I Mutation

While a KCND3 V392I mutation uniquely displays a mixed electrophysiological phenotype of Kv4.3, only limited clinical information on the mutation carriers is available. We report two teenage siblings exhibiting both cardiac (early repolarization syndrome and paroxysmal atrial fibrillation) and cerebral phenotypes (epilepsy and intellectual disability), in whom we identified the KCND3 V392I mutation. We propose a link between the KCND3 mutation with a mixed electrophysiological phenotype and cardiocerebral phenotypes, which may be defined as a novel cardiocerebral channelopathy.

Therapy-Resistant Ventricular Arrhythmias Developed More Often in Advanced Than in Therapeutic Mild Hypothermic Condition

Therapy-resistant ventricular arrhythmias can occur during accidental advanced hypothermic conditions. On the other hand, hypothermic therapy using mild cooling has been successfully accomplished with infrequent ventricular arrhythmia events.To further clarify the therapeutic-resistant arrhythmogenic substrate which develops in hypothermic conditions, an experimental study was performed using a perfusion wedge preparation model of porcine ventricle, and electrophysiological characteristics, inducibility of ventricular arrhythmias, and effects of therapeutic interventions were assessed at 3 target temperatures (37, 32 and 28°C).As the myocardial temperature decreased, myocardial contractions and the number of spontaneous beats deceased. Depolarization (QRS width, stimulus-QRS interval) and repolarization (QT interval, ERP) parameters progressively increased, and dispersion of the ventricular repolarization increased. At 28°C, VF tended to be inducible more frequently (1/11 at 37°C, 1/11 at 32°C, and 5/11 hearts at 28°C), and some VFs at 28°C required greater defibrillation energy to resume basic rhythm.An advanced but not a mild hypothermic condition had an enhanced arrhythmogenic potential in our model. In the advanced hypothermic condition, VF with relatively prolonged F-F intervals and a greater defibrillation energy were occasionally inducible based on the arrhythmogenic substrate characterized as slowed conduction and prolonged repolarization of the ventricle.