Congenital long QT syndrome (LQTS) is characterized by prolongation of the QT interval and T wave abnormalities on electrocardiogram (ECG). The prolongation of QT interval (manifestation of prolongation of ventricular repolarization) predisposes to syncope, seizure and sudden cardiac death due to typical polymorphic ventricular tachycardia torsade de pointes or ventricular fibrillation. Long QT syndrome may associate with deafness as Jervell and Lange-Nielsen syndrome, described in 1957, which is very rare and later described Romano-Ward syndrome without deafness affecting 1 in 2500-5000 persons. LQTS is hereditary disorder, genetically heterogeneous, caused by mutations in specific cardiac ion channel genes. The most prevalent form of LQTS is LQT1 with mutation on KCNQ1 gene encoding cardiac potassium IKs channel protein. The result of the mutation is incorrect function of the channel. Genetic tests are important for identification of a mutation. Diagnosis of long QT syndrome may be difficult and sometimes we need several recorded electrocardiograms to find QT interval prolongation. The Schwartz and Moss clinical criteria may be steel useful for LQTS diagnosis. Beta-blockers are effective in patients with long QT syndrome and should be administered at diagnosis. Patients should avoid as physical and emotional stresses, as drugs prolonged corrected QT interval. It is necessary to examine the family members. We present a patient with genetically documented familiar LQT1 syndrome. Diagnostic problems, symptoms and therapy are discussed.

LQT1 syndrome, electrocardiographic diagnosis, molecular tests, familiar mutation, treatment