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Long QT syndrome is a rare disorder of cardiac ion channels, characterised by a prolonged QT interval and T-wave abnormalities on electrocardiogram (ECG) and the occurrence of the ventricular tachycardia torsade de pointes. Sodium, potassium or calcium channels present in heart muscle may be affected, altering the regulation of electrical current in the cells [1-3]. Individuals with this condition will be predisposed to cardiac events such as arrhythmias and polymorphic ventricular tachycardia, which may lead, if untreated, to sudden cardiac death [2,3]. Thirteen genes are associated with the condition, and hundreds of mutations have been identified [3-5]. Currently, more than 95% of the pathogenic mutations listed in disease databases (Gene Connection For the Heart, http://www.fsm.it/cardmoc/; online Hu‐ man Gene Mutation Database, www.hgmd.cf.ac.uk/) are sequence variants (including point mutations and small insertions or deletions), but the importance of whole or multi-exon de‐ letions and duplications has more recently been recognised [6] and it is now recommended to use both sequence and dosage techniques in order to provide comprehensive analysis [3]. |
