A Missense Mutation in a Highly Conserved Region of CASQ2 Is Associated with Autosomal Recessive Catecholamine-induced Polymorphic Ventricular Tachycardia in Bedouin Families from Israel

Sudden death due to cardiac arrhythmia is a devastating event, especially when it occurs in children. In the absence of structural heart defects, five major arrhythmogenic disorders manifesting as polymorphic ventriculartachycardia (PVT) and/or ventricular fibrillation havebeen described: the long QT syndrome, right bundlebranch block and persistent ST elevations (Brugada syndrome), the "short coupled variant of torsade de pointes,"idiopathic ventricular fibrillation with normal electrocardiogram, and PVT induced by catecholamines (Viskinand Belhassen 1998). The last entity was initially described as a case report in 1975 (Reid et al. 1975) and asa distinct clinical entity in 1995 (Leenhardt et al. 1995).Catecholamine-induced PVT is a rare disease that occursin subjects without obvious organic heart disease, characterized by episodes of syncope, seizures, or sudden deathin response to physiological or emotional stress (Viskinand Belhassen 1998). Leenhardt et al. described 21 children (mean ± S.D. age, 9.9 ± 4 years) with no organic heartdisease and normal baseline ECG (except for sinus bradycardia), who suffered from episodes of syncope andseizures usually related to physiological or emotionalstress. The mean age at which the first syncope occurredwas 7.8 ± 4 years. They had no structural heart diseaseand a normal QT interval. In 30% of the patients therewas a family history of syncope or sudden death. Interestingly, the ventricular tachycardia (VT) could be reproduced in these patients either by a treadmill exercise testor by infusing small amounts of isoproterenol at a ratesufficient to accelerate the cardiac rate to 150–160 beatsper minute. Following treatment with beta-blockers, thepatients' symptoms underwent almost complete resolution, and no episodes of VT could be found on 24-hourholter monitoring. PVT affects mainly children, but infants (Shaw 1981) as well as adults (Eisenberg et al.1995) have also been reported as affected...