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Background: Adenosine may play a role in the pathogenesis of vasovagal syncope (VVS). The aim of the study was to evaluate the adenosine A(2A) receptor gene 1083 T > C polymorphism in patients with syncope and its possible association with results of head-up tilt test (HUT)., Methods: Three hundred and forty-seven consecutive patients (mean age 47.3 ± 18.5 years, 132 men, 215 women) with one or more syncopal episodes underwent HUT as part of standardized diagnostic evaluation. HUT was positive in 207 patients (75 males, mean age 44.7 ± 18.6 years) and negative in 140 patients (58 males, mean age 48.17 ± 18.8 years). One thousand and eighty-three T > C single nucleotide polymorphism in the adenosine A(2A) receptor gene (rs5751876) was evaluated in 347 patients with syncope and in 85 subjects without history of syncope (54 men, mean age 41.7 ± 16.3)., Results: Adenosine A(2A) receptor 1083 T > C polymorphism was not associated with the positivity of HUT. Blood pressure and heart rate response to tilting was similar in all genotypes. Low frequency (LF) power was significantly lower in CC genotype compared to CT genotype in early phase of tilt (log LF 2.69 ± 0.61 vs 3.20 ± 0.60; P = 0.01) and at the time of syncope (log LF 2.60 ± 0.63 vs 2.77 ± 0.48; P = 0.04)., Conclusions: Adenosine A(2A) receptor 1083 T > C polymorphism is not associated with the positivity of HUT and its proposed role in predisposition to VVS was not confirmed. CC genotype may be associated with lower sympathetic activity during HUT., (© 2015 Wiley Periodicals, Inc.)

Background: Vasovagal syncope is a common clinical condition, consequential to reduced cerebral blood flow resulting from a failure in cardiovascular homeostasis during orthostasis. Blood pressure regulation is the basis for syncope development. In this regulation, the α1a-adrenergic receptor plays a major role. Some studies have found a positive correlation between the Arg347Cys polymorphism of the α1a-adrenergic receptor to hypertension and heart autonomic control. The goal of this study is to evaluate the possible association between the Arg347Cys α1a-adrenergic receptor polymorphism and vasovagal syncope in a Mexican population., Methods/major Findings: A sample of 89 vasovagal syncope patients and 40 healthy controls were studied. Arg347Cys α1a-adrenergic receptor polymorphism was determined by the PCR-RFLP method. We found an increased frequency of genotype ArgArg in vasovagal syncope patients. In a logistic regression model significant associations were found in two genetic models, in codominant model (OR=13.21: CI 95% 3.69-54.99, p<0.001) and in additive model (OR=12.68: CI 95% 3.5-53.07, p<0.001) for ArgArg genotype with CysCys as reference., Conclusions: Our data suggests an important participation of Arg347Cys polymorphism as susceptibility factor in patients with vasovagal syncope. ArgArg genotype could be a marker for vasovagal syncope susceptibility in the Mexican population., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Objective: Vasovagal syncope (VVS) is the most frequent type of syncope and a common differential diagnosis of epilepsy. The role of genetic factors in VVS is debated. We performed a twin-family study to clarify this question and to analyze the putative mode of inheritance., Methods: Fifty-one same-sex twin pairs where at least 1 had syncope were ascertained. The twins were interviewed via telephone using a standardized questionnaire. Available medical records were obtained. Information on the affected status of first- and second-degree relatives was acquired., Results: There was a trend toward higher casewise concordance in monozygous (MZ, 0.75) than dizygous (DZ, 0.50) twins for any syncope (p = 0.06). Significant and strong effects on concordance between MZ and DZ twins were found for fainting at least twice unrelated to external circumstances (0.71 vs 0.27, p = 0.018) and for syncope associated with typical vasovagal triggers (0.62 vs 0.00, p < 0.001). Twelve of 19 concordant MZ twin pairs reported sparse or no other affected family members whereas in the other 7 pairs multiple close relatives were affected., Conclusions: The twin analysis provides strong evidence for the relevance of genetic factors in VVS. Analysis of the families suggests that complex inheritance (multiple genes ± environmental factors) is usual, with rarer families possibly segregating a major autosomal dominant gene.

Objective: A handful of studies suggest a familial predisposition to vasovagal syncope (WS) but the scope of information available to date is poor. The aim of our study was to evaluate the prevalence of vasovagal syncope and its familial occurrence in the young., Methods and Results: The studied group consisted of 281 women and 111 men, aged 18-32 years. Forty-seven percent of the population had one brother or sister, and the mean number of individuals per family was 4.4 +/- 1.0. The questionnaire consisted of 30 questions regarding syncopal history. Syncope was reported in 32.1% of the patients studied (36.7% in women vs. 20.7% in men; P < 0.05), 29.1% of mothers, 16.8% of fathers, 30.9% of sisters and 14.2% of brothers. Logistic regression analysis revealed that positive history regarding the syncope in the whole group of students was related to the female gender (OR 2.17; CI: 1.28-3.7), the history of a syncope in mother (OR 1.74; CI: 1.09-2.78) and the history of a syncope in father (OR 2.22; CI: 1.28-3.86; P < 0.001)., Conclusions: A positive history of syncope in male relatives increases the risk of syncope in men and women, whereas a positive history of syncope in female relatives increases the risk of syncope in women only. Female gender independently of the family history increases the risk of syncope. The genetics of the vasovagal syncope could be polygenic but the mechanisms of a transmission remain unclear to date.

Although the pathophysiology of vasovagal syncope is not completely understood, the involvement of sympathetic nervous system alterations has been suggested. Since predisposition to fainting during orthostatic challenge may be associated with genetic variations, we sought to explore the role of genetic polymorphisms affecting sympathetic nervous system function in the susceptibility to tilt-induced vasovagal syncope. We genotyped 129 subjects with recurrent unexplained syncope who underwent tilt testing, and investigated the recurrence of syncope. The analysed polymorphisms were Arg492Cys (ADRA1A gene), Ser49Gly and Arg389Gly (ADRB1), Arg16Gly and Gln27Glu (ADRB2), 825C/T (GNB3), -1021C/T (DBH) and S/L (SLC6A4). No association of the aforementioned genetic variants with both tilt test outcomes and new syncopal episodes during follow-up was found. None of the considered polymorphisms influencing sympathetic activity is a major risk factor for vasovagal syncope in Italian patients., (.)

Unlabelled: An impairment of cardiovascular reflexes may be the result of functional alterations in the G proteins intracellular signaling produced by functional genes' polymorphisms. The aim was to evaluate the relationships between single nucleotide polymorphisms in genes encoding G-proteins signaling pathways and syncopal patients with severe clinical manifestation., Methods and Results: From 307 syncopal patients free from any other diseases 83 (27%) had at least one malignant episode of syncope with a significant injury as fractures. There was 1.9 malignant spells per patient. All patients were tilted and genotyped by polymerase chain reaction followed by restriction fragment length polymorphism method. 74 healthy volunteers with negative history of syncope constituted the control group were also genotyped. Following polymorphisms were detected: C393T in gene encoding the alfa-subunit of Gs-protein (GNAS1), C825T of gene for G-protein beta 3 subunit (GNB3) and C1114G for the gene of cardiac regulator of G-protein signaling (RGS2). We found an association with lower risk of malignant syncope in positive tilting patients during passive phase of the test compared to NTG-enhanced (OR 0.38; 95% CI 0.15-0.95; P=0.04). No difference between healthy controls and patients in the alleles frequency was found (P>0.05). Neither the 393T allele of GNAS1 and 825T allele of GNB3 nor 1114G allele of RGS2 was associated with enhanced risk of severe clinical manifestation (P>0.05)., Conclusions: The studied single nucleotide polymorphisms of genes encoding G-proteins signaling pathways seem to be not connected with the severe clinical manifestation of syncope.

Objectives: As the endothelin system participates in the regulation of cardiovascular homeostasis, the aim of this study was to analyse the role of endothelin system polymorphisms in influencing tilt-induced vasovagal syncope., Methods: We evaluated 107 otherwise healthy subjects with recurrent unexplained syncope who underwent a head-up tilt test. All subjects were genotyped for the 3A/4A polymorphism of the EDN1 gene and the H323H T/C polymorphism of the EDNRA gene., Results: Fifty-eight patients (54%) fainted. In terms of the EDNRA polymorphism, eight subjects (8%) had the T/T genotype, 41 were heterozygous (38%) and 58 homozygous (54%) for the C allele. Sixty subjects (56%) carried homozygosis for the 3A allele of the EDN1 polymorphism and 47 were heterozygous (44%). The 4A allele was significantly more frequent in the patients who responded positively to the tilt test than in those who did not: the relative odds ratios and confidence intervals at univariate and multivariate analyses were respectively 2.37 (1.07-5.26) and 2.41 (1.05-5.49). Comparisons with a control group further supported these data. Among the tilt-positive patients, the carriers of the 4A allele were more likely to have a vasodepressive pattern than those who were homozygous for the 3A variant., Interpretation: The 3A/4A polymorphism of the EDN1 gene affects susceptibility to syncope, and the 4A variant associated with increased endothelin-1 expression may promote vasodepressive hemodynamic responses during tilt testing.

Objective: To investigate a possible familial predisposition in neurocardiogenic syncope., Methods: Cross-sectional survey with 252 subjects, with positive familial history for syncope, who underwent head-up tilt-test (TT) at Instituto de Cardiologia do Rio Grande do Sul, between September 2001 and September 2005. The relationship between familial history for neurocardiogenic syncope and TT result was analysed., Results: Familial history for neurocardiogenic syncope was identified in 40% (49/126 cases) of subjects with positive tilt-test results and 25% (31/126 ) of those with negative TT., Conclusion: There is a correlation between familial history for neurocardiogenic syncope and its occurence. A genetic component can possibly explain this relationship.

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.