Lack of association between genetic polymorphisms affecting sympathetic activity and tilt-induced vasovagal syncope.

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.