OBJECTIVE: Hereditary long QT syndrome (LQTS) is a cardiac disorder 
characterized by prolongation of QT interval on electrocardiograms (ECGs) and 
syncope and sudden death caused by a specific multi-polymorphic ventricular 
tachyarrhythmia known as torsade de pointes. LQTS is caused by mutations in 
cardiac sodium channel gene SCN5A; potassium channel subunit genes KCNQ1, KCNH2, 
KCNE1, KCNE2, KCNJ2; calcium channel gene Cav2.1. and ankyrin-B gene ANK2.
METHODS: We characterized 77 Chinese LQTS patients with clinical manifestations 
and mutations in the main LQTS genes, KCNQ1 and KCNH2 using PCR and sequence 
analysis.
RESULTS: The spectrum of ST-T-wave patterns of 24 (31.2%) probands were 
considered as LQT1, 42 (54.5%) as LQT2 and 3 (3.9%) as LQT3. The remaining 8 
(10.3%) could not be characterized. The average age for this population of LQTS 
patients was (27.6 +/- 16.4) years and the average QTc (561 +/- 70) ms, and the 
age of the first syncopal attack was (17.6 +/- 14.7) years. The triggering 
factors for cardiac events happening in these mutation carriers included 
physical exercise, emotional excitement and auditory irritation. We identified 4 
KCNQ1 mutations and 7 KCNH2 mutations. Six of them were first identified with 
some data already shown. In this paper we showed the data of 6 other mutations.
CONCLUSIONS: LQT2 is the most common type of LQTS in Chinese; 2 mutations of 
KCNQ1 and KCNH2 were first identified in this report; there are some differences 
between Chinese and North American or European LQTS patients in clinical 
characters and ECG.