The Department of Pediatric Cardiology, Medical University of Silesia in 
Katowice-Ligota, studied 24 patients with clinically diagnosed (using ECG) 
long-QT syndrome (LQTS) in 18 cases. Nine patients were diagnosed with LQT1 and 
nine with LQT2. The other six individuals were healthy, with no symptoms 
characteristic for prolonged QT syndrome, but came from families with confirmed 
disease occurrence. The study was conducted on members of four families. In 
order to search for mutations (using mSSCP and sequencing), genomic DNA was 
obtained from patients to determine the expression levels of the genes KCNQ1 and 
KCNH2 (HERG), involved in the occurrence of clinical signs of disease. Total RNA 
was extracted from peripheral blood. Consent to the use of blood samples of 
patients had been given by the Bioethics Commission of the Medical University of 
Silesia. mSSCP analysis and sequencing did not confirm the occurrence of 
mutations in KCNQ1 and HERG associated with the occurrence of LQTS. Analysis of 
gene expression profile of KCNQ1 and HERG confirmed the presence of disease in 
people with a known clinical diagnosis. Overexpression, as well as reduced 
expression, was observed for the examined genes. KCNQ1 was inhibited in two 
families, whereas HERG was reduced in one and overexpressed in the other. Gene 
expression profile analysis showed abnormal expressions of KCNQ1 and HERG in 
healthy subjects, which may be a sign of predisposition to develop the disease. 
The novelty of our study involved the use of total mRNA isolated from human 
peripheral blood, and the very limited evidence in the literature to date 
regarding the assessment of gene expression profile of HERG and KCNQ1 in 
relation to the presence of prolonged QT syndrome.