Abstract 2257: KCNJ2 Mutations in Patients Referred for Catecholaminergic Polymorphic Ventricular Tachycardia Gene Screening
Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease characterized by adrenergically mediated polymorphic or bidirectional ventricular tachycardia (BVT). Andersen-Tawil syndrome (ATS1), which are mainly caused by KCNJ2 mutations, phenocopies CPVT and may manifest the typical adrenergically mediated BVT. The purpose of this study was assess whether patients (pts) lacking periodic paralysis typical of ATS1 and diagnosed as CPVT because of BVT carry KCNJ2 mutations.
Methods and Results: Mutational analysis of KCNJ2 was performed in 23 RyR2 and CASQ2 genotype-negative CPVT pts with normal QT interval. Two novel missense mutations (S220I and T305I) were identified. Mutations were absent in >400 reference alleles. Both of the pts present exercise or isoproterenol induced BVT, baseline ECG with prominent U wave and mild facial abnormalities. In vitro characterization showed that no current is detectable when S220I and T305I mutants clones are expressed; on the contrary co-expression of WT and mutant KCNJ2 to mimic heterozygosis present in patients, caused significant dominant negative effect (see figure⇓). Confocal laser microscopy revealed normal sarcolemmal localization of the mutant channels and of the heterozygous channels.
KCNJ2 mutation with loss of function are present in a minority of pts with clinical diagnosis of CPVT.
Given the limited number of CPVT pts with KCNJ2 mutations it is impossible to determine whether their prognosis is identical to that of RyR2 and CASQ2 related CPVT.
Screening of KCNJ2 should be considered in CPVT pts without mutations in RyR2 and CASQ2 genes.