RESUMO
Ohjective To investigate the associations between the Arg389Gly polymorphism of the β_1-adrenergiecreceptor gene (ADRB1) and vasovagal syncope (VVS) in Chinese children. Methods Genotype of ADRB1 was determined by polymerase chain reaction-restriction fragment length pelymorphism analysis. Case-control studies and quantitative trait analysis were carried out by comparing between carriers (one or two copies of the Gly389 allele) and non-carriers (Arg389 genotype) of the ADRBI in 54 patients with unexplained syncope and in 54 healthy control subjects. Patients were subdivided into two groups according to head up tilt test (HUTT) : positive HUTT, known as VVS group and negative HUTT group. Distribution of Arg389Gly genetype in VVS group and the relationship to three clinical patterns were also analyzed. Results An allele frequency of Arg389 was 73.15% and Gly389 was 26.85% in healthy subjects. Higher Gly389 allele frequency was found in VVS group (n = 30) than that in negative HUTT group (33.33% vs. 14.58%, P < 0.05). In VVS group, the frequencies of the Gly389 allele in cardioinhibitory pattern (n = 6), mixed pattern (n = 9) and vasodepressor pattern (n = 15) was 66.67%, 33.3% and 23.33%, respectively, which had significant differences between the cardioinhibitory pattern from any of the other two patterns (both P < 0.05). Conclusions An association of positive HUTT with a single nucleotide pelymorphism of Gly to Arg switch at position 389 of the ADRB1 was found. This polymorphism may contribute to susceptibility to VVS.