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Objectives: The aim of this prospective study was to investigate the impact of genetic polymorphisms of β3 subunit of G-protein on the occurrence of vasovagal syncope, hemodynamic parameters and heart rate variability during head-up tilt test (HUT)., Background: G-proteins play an important role in the intracellular transmission of impulses in cardiovascular autonomic reflexes., Methods: In 157 patients with suspected vasovagal syncope HUT was performed. Ninety-one patients (38 men, 53 women, mean age 48 ± 17 years) had positive HUT. Control group consisted of 109 subjects (69 men, 40 women, mean age 37 ± 16 years) with no history of syncope. Results of HUT, hemodynamic parameters and LF, HF, LF/HF, SDNN, RMSSD parameters of heart rate variability were compared in patients with different genotypes. C825T polymorphism of β3 subunit of G-protein was determined in the study subjects., Results: There was no significant difference in the distribution of genotypes between patients and control group. Also, there was no significant difference in hemodynamic parameters. A statistically significant difference was found between genotypes in LF/HF in the early HUT (mean rank CC: 48.68 vs CT: 35.51 vs TT: 34.14; p = 0.039) and at RMSSD at the time of syncope (mean rank CC: 32.38 vs CT: 42.74 vs TT: 18.50; p = 0.026)., Conclusions: In this study, the relation of C825T polymorphism of β3 subunit of G-protein to vasovagal syncope was not documented (Tab. 2, Fig. 4, Ref. 37).

Objective: Investigate the association between GNB3C825T gene polymorphism and pediatric vasovagal syncope., Method: Syncope group consisted of 54 cases of unexplained syncope in children, including 18 males and 36 females, at the age of 11.8 years; control group consisted of 54 healthy children over the same period, of whom 20 were male and 34 female, at the age of 11.2 years. The patients underwent head-up tilt test (HUTT). According to HUTT test results, HUTT-positive group and HUTT-negative group were further classified. For cases in HUTT-positive group, based on the changes in blood pressure and in heart rate during HUTT, vasodepressor, mixed and cardioinhibitory patterns were studied. DNA was extracted from peripheral blood in all the patients. A pair of primers was designed flanking 825 polymorphic loci. Products were recovered by using polymerase chain reaction (PCR). GNB3C825T polymorphism was detected by using gene-side GNB3C825T sequencing. Allele distribution between the various groups were studied., Result: Among fifty-four children with syncope, HUTT was positive in 30 cases, including vasodepressor pattern in 15 cases (50.0%), mixed pattern in 9 cases (30.0%) and cardioinhibitory pattern in 6 cases (20.0%). Whereas the subjects in control group had negative HUTT response. GNB3C825T allele C in the control and syncope groups was 81.5% and 65.7%, respectively. GNB3C825T allele T in the control and syncope groups was 18.5% and 34.3%, respectively (χ(2) = 6.888, P < 0.05). GNB3C825T allele C in HUTT-positive and negative groups was 61.7% and 81.3%, respectively. And GNB3C825T allele T in HUTT-positive and negative groups was 38.3% and 18.7%, respectively (χ(2) = 4.905, P < 0.05). GNB3C825T allele frequency did not show statistically significant difference among the 3 hemodynamic patterns of VVS (χ(2) = 0.658, P > 0.05)., Conclusion: Study on GNB3C825T allele frequency in children with vasovagal syncope is of significant value for a better understanding of the pathophysiology of VVS and provide a molecular biologic basis for its mechanisms.

Objective: The G protein is responsible for signal intracellular transduction and participates in cardiovascular reflexes. C825T polymorphism of the gene encodes the B3 subunit of G protein (GNB3) and causes the increased intracellular signal transduction. The aim was the evaluation GNB3 C825T polymorphism manifestation in vasovagal patients with no other diseases., Methods: In 68 positive tilted patients genomic DNA was extracted from blood using an extraction kit. The GNB3 C825T polymorphism was diagnosed by restriction of the PCR amplicon with BseDI (MBI Fermentas). All patients were genotyped and next analyzed in regard to typical vasovagal history., Results: The prevalence of genotype CC was 38%. Genotypes CT and TT were found equally in 31% of cases. The C allele in comparison to the T allele appeared in 54% vs 46% (p>0.05). Typical vasovagal history was present in 83% of patients. The frequency of GNB3 825T allele was significantly higher in patients with non-typical vasovagal history than in group with typical history (p<0.001)., Conclusions: Genotype CC GNB3 is the most popular in vasovagal patients. The predisposition to vasovagal syncope seems to be not associated with the GNB3 825T allele. Further studies are planned to clarify the genotype/phenotype relationship in vasovagal patients.