Disorders of cardiac repolarization: long QT and short QT syndromes.

The long and short QT syndromes are heterogeneous diseases characterized by abnormal ventricular repolarization and episodes of syncope and/or life-threatening cardiac arrhythmias. Several disease-causing genes have been identified, including those encoding cardiac ion channel-composing proteins. The clinical determination of genotype offers a striking benefit: diagnosis, prediction of clinical phenotype, risk stratification, clinical and genetic counseling, and introduction of therapy. Genetic testing is of special importance for the genotyped patient's family members to prevent unexpected cardiac death. By means of recently advanced methodology in molecular genetics and electrophysiology it is expected that novel genes responsible for these disease entities will be identified.