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Objective: To explore the relationship between electrocardiographic (ECG) and genetic mutations of patients with hypertrophic cardiomyopathy (HCM), and early ECG changes in HCM patients., Methods: Clinical, 12-lead ECG and echocardiographic examination as well as genetic examinations were made in a three-generation Chinses HCM pedigree with 8 family members (4 males). The clinical characterization and ECG parameters were analyzed and their relationship with genotypes in the family was explored., Results: Four missense mutations (MYH7-H1717Q, MYLK2-K324E, KCNQ1-R190W, TMEM70-I147T) were detected in this pedigree. The proband carried all 4 mutations and 5 members carried 2 mutations. Corrected QTc interval of KCNQ1-H1717Q carriers was significantly prolonged and was consistent with the ECG characterization of long QT syndrome. MYLK2-K324E and KCNQ1-R190W carriers presented with Q wave and(or) depressed ST segment, as well as flatted or reversed T waves in leads from anterolateral and inferior ventricular walls. ECG results showed ST segment depression, flat and inverted T wave in the gene mutation carriers with normal echocardiographic examination results. ECG and echocardiographic results were normal in TMEM70-I147T mutation carrier., Conclusions: The combined mutations of the genes associated with cardiac ion channels and HCM are linked with the ECG phenotype changes in this HCM pedigree. The variations in ECG parameters due to the genetic mutation appear earlier than the echocardiography and clinical manifestations. Variation in ECG may become one of the indexes for early diagnostic screening and disease progression of the HCM gene mutation carriers.

Objective: To search for the mutations of potassium voltage-gated channel, KQT-like subfamily member 1(KCNQ1) gene in 31 Chinese long QT syndrome(LQTS) families., Methods: Due to the genetic heterogeneity, the genotype of patients was first predicted based on the spectrum of ST-T-wave patterns on ECG. Ten of 31 probands were considered as LQT1. Then the mutation of KCNQ1 gene was screened by the polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) technique combined with DNA sequencing in all members of these 10 families. To avoid omitting some LQT1 patients without typical characteristics and also to do methodological comparison, the mutations of KCNQ1 gene on 16 exons were screened by PCR and direct DNA sequencing in the rest 21 non-LQT1 probands only. Co-segregation analysis was carried out after the finding of an abnormal sequence. In case that the abnormality existed in patients only, the test of such exon was performed in 50 irrelevant normal individuals., Results: Two missense mutations and three single nucleotide polymorphisms (SNPs) were found in the LQT1 predicted families. The two mutations were S277L (1 family) and G306V (1 family) in exon 5 and were not reported previously. Three polymorphisms were 435C-->T (7 families), 1632C-->A (1 family), and IVS1+9 C-->G (3 families). Only a splice mutation IVS1+5G-->A (2 families) and a polymorphism IVS10+18C-->T (1 family) were found in the non-LQT1 predicted probands. All three mutations were localized within the functional domain of KCNQ1 and were co-segregated with the disease, and were not found in 50 normal individuals., Conclusion: Two novel missense mutations, 1 splice mutation and four SNPs on KCNQ1 gene were found in the 31 LQTS families. Combined with ECG-based genotype prediction, PCR-SSCP could find most mutations on KCNQ1 and be a simple and economic method for screening LQTS.

Objective: Congenital long QT syndrome (LQTS) is an inherited disorder of cardiac repolarization characterized by prolongation of QT interval and polymorphic ventricular tachycardia torsade de pointes (TdP) in the electrocardiogram (ECG). Clinical symptoms include recurrent syncope, seizure or even sudden death. It is caused by mutations of at least seven genes, six of them encoding ion channels that determine the duration of ventricular action potentials. One of these genes, KCNQ1, encodes an alpha-subunit of cardiac slowly activated delayed rectifier potassium channel. Patients carrying mutations of KCNQ1 are named as LQT1, which accounts for 42% of patients with LQTS. This study sought to analyze the clinical data of Chinese with LQTS and to screen for the mutations of KCNQ1., Methods: The universally accepted phenotypic criteria of LQTS was used for identification of probands. There were six families with LQTS. They were enrolled in this study. Clinical and ECG data of each family member were recorded. Genomic DNA was prepared from peripheral blood lymphocytes. Polymerase chain reaction-single strand conformation polymorphism analysis was used to screen for mutations throughout the whole coding region of KCNQ1 and DNA sequencing was performed to determine the exact mutation site., Results: There were totally 13 patients in the six LQTS families. Five were male and eight female. One suffered from sudden death, 10 had syncope and 2 were asymptomatic. Eleven of the 13 patients had ECG data. Their QT and QTc (mean +/- SD) were (0.460 +/- 0.058) s and (0.516 +/- 0.058) s, respectively. TdP was observed in 3 patients (27%) during the syncope attack. By PCR-SSCP analysis, two novel KCNQ1 deletion mutations 356-357 Delta QQ and 626-631 Delta GSGGPP were identified in 7 patients of 2 families. None of 50 normal individuals carried these mutations, indicating these two mutations were likely to cause the disease. In addition, P448R was found in one affected and some unaffected members in other two families and in 7 of 50 (14%) normal individuals, indicating that this might be a polymorphism. All the three mutations located in C-terminal domain of KCNQ1 protein., Conclusions: Two novel deletion mutations and one novel polymorphism of KCNQ1 gene were identified among 6 Chinese families with LQTS.